Download Dietary Differences between Vegetarian and Omnivore in College

DIETARY DIFFERENCES BETWEEN VEGETARIAN AND OMNIVORE IN
COLLEGE STUDENTS
A Thesis
Presented to the
Faculty of
California State Polytechnic University, Pomona
In Partial Fulfillment
Of the Requirements for the Degree
Master of Science
in
Agriculture
By
Stephanie Bunawan
2015
SIGNATURE PAGE
THESIS:
DIETARY DIFFERENCES BETWEEN VEGETARIAN
AND OMNIVORE IN COLLEGE STUDENTS
AUTHOR:
Stephanie Bunawan
DATE SUBMITTED:
Fall 2015
College of Agriculture
Dr. Bonny Burns-Whitmore, R.D. _________________________________________
Thesis Committee Chair
Human Nutrition and Food Science
Dr. David Edens
_________________________________________
Human Nutrition and Food Science
Aleida Gordon , MPH, R.D.
_________________________________________
Human Nutrition and Food Science
ii
ACKNOWLEDGEMENTS
I would like to thank my advisor Dr. Bonny Burns-Whitmore. Thank you for
being patient and believing in me. Thank you for being my thesis committee chair, for
your constant support throughout this process all these years. Thank you Ms Aleida
Gordon for agreeing to be on the committee since my first year in here. Thank you for
helping me with my thesis and your support in my career goal. Thank you Dr. David
Edens for agreeing to be on the committee. Thank you for your help on the data and the
statistical analysis. Thank you Dr. Bidlack for agreeing to be in my past committee and
your support and kindness during my school year. I would like to also thank Dr. Gina
Siapco for your contributing help at Loma Linda University to the success of this thesis.
Thank you to all of my professors during my studies here. I would also like to thank my
family, my mom and dad for their love, support, and patience in me toward finishing my
master program. Lastly, thank you for all students who volunteered to participate in this
study, as well as research assistants, without you, this study would not be possible.
iii
ABSTRACT
The numbers of the vegetarians in the United States (US) are steadily increasing,
with 21% of college students are vegetarians. Vegetarian diet has been associated with
lower risks of certain chronic diseases; however, vegetarians may have nutrient risks due
to certain food limitation in their diets. The purpose of this study was to assess the
difference in dietary intake of vegetarians and omnivores diet in college students and to
determine whether each diet group meets the Dietary Reference Intakes (DRI) of
America. Thirty three18-35 years old college students completed five-day food and
activity records, they were then grouped into vegetarian group (n=12) and omnivore
group (n=21) based on the self-reported food records. The dietary intakes of both groups
were then compared to the DRIs. Vegetarians had lower intakes of protein, saturated fat,
cholesterol, selenium, and sodium; and higher intakes in fiber, vitamin A, beta-carotene,
vitamin K, copper, and magnesium when compared to omnivores. Vegetarians did not
reach the DRIs recommendation for n-3 PUFA, n-6 PUFA, vitamin D, calcium,
chromium, selenium, and choline. Omnivores had lower intakes than RDIs in dietary
fiber, vitamin D, folate, vitamin K, calcium, chromium, iron, magnesium, molybdenum,
and choline. At the macronutrient level, vegetarian diet was in better accordance with
DRIs than omnivore diet. At the micronutrient level, both groups fall short in certain
nutrients, suggesting a need for greater attention to ensure adequate diet of specific
nutrients.
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TABLE OF CONTENTS
Signature Page .................................................................................................................... ii
Acknowledgements ............................................................................................................ iii
Abstract .............................................................................................................................. iv
List of Tables ................................................................................................................... viii
List of Figures .................................................................................................................. viii
Chapter 1: Introduction ....................................................................................................... 1
Definitions ....................................................................................... 4
Abbreviations ................................................................................... 5
Chapter 2: Literature Review .............................................................................................. 7
Dietary Intakes ................................................................................. 8
Energy ......................................................................................................... 8
Carbohydrate ............................................................................................... 9
Protein ......................................................................................................... 9
Fat and Saturated Fat ................................................................................ 10
N-3 PUFAs................................................................................................ 10
Iron ............................................................................................................ 11
Calcium ..................................................................................................... 12
Vitamin D.................................................................................................. 13
Vitamin B12 .............................................................................................. 14
Statement of Problem ...................................................................... 19
Statement of Purpose ...................................................................... 19
Hypotheses ..................................................................................... 19
v
Significance of The Study ............................................................... 20
Assumptions ................................................................................... 20
Chapter 3: Methods ........................................................................................................... 21
Participants .................................................................................... 21
Recruitment .................................................................................... 21
Dietary Assessment ........................................................................ 22
Limitations and Delimitations ......................................................... 23
Chapter 4: Results ............................................................................................................. 26
Chapter 5: Discussion ....................................................................................................... 33
Macronutrients ............................................................................... 33
Energy ....................................................................................................... 33
Protein ....................................................................................................... 33
Fat ............................................................................................................. 34
N-3 pufa .................................................................................................... 35
Fiber .......................................................................................................... 36
Micronutrients ................................................................................ 37
Vitamin B12 ............................................................................................. 37
Vitamin D.................................................................................................. 39
Calcium ..................................................................................................... 40
Iron ............................................................................................................ 41
Zinc ........................................................................................................... 42
Chapter 6: Conclusion....................................................................................................... 44
References ......................................................................................................................... 49
vi
Appendix A IRB Approval Forms .................................................................................... 60
Appendix B Sample of Consent Form .............................................................................. 63
Appendix C Screening Questionnaire ............................................................................... 64
Appendix D Sample of Food and Activity Record ........................................................... 66
Appendix E Sample of Recruitment Flyer ........................................................................ 72
Appendix F Journal Article............................................................................................... 73
vii
LIST OF TABLES
Table 1
A Summary of Vegetarian Studies from Literature Review ............................ 15
Table 2
Participant characteristics by diet group .......................................................... 26
Table 3
Dietary intake (including supplements) analysis between omnivore and
vegetarian groups ............................................................................................. 27
Table 4
Macronutrient intake (including supplement) between female vegetarians and
female omnivores ............................................................................................. 29
Table 5
Dietary intake of vitamins and minerals (including supplement) between
female vegetarians and female omnivores ....................................................... 30
Table 6
Recommended Dietary Allowance (RDA), Adequate Intake (AI), and
Estimated Average Requirement (EAR) comparison to omnivore and
vegetarian group ............................................................................................... 32
Table 7
n-3 PUFA results between omnivores and vegetarians (include and exclude
supplements) ..................................................................................................... 35
Table 8
n-3 PUFA comparison of Recommended Dietary Allowance (RDA),
Adequate Intake (AI), and Estimated Average Requirement (EAR) to
omnivore and vegetarian groups (include and exclude supplements) .............. 36
Table 9
Vitamin B12 results between omnivores and vegetarians (include and
exclude supplements) ....................................................................................... 38
Table 10 Vitamin B12 comparison of Recommended Dietary Allowance (RDA),
Adequate Intake (AI), and Estimated Average Requirement (EAR) to
omnivore and vegetarian groups (include and exclude supplements) .............. 38
viii
LIST OF FIGURES
Figure 1. Flowchart of recruitment and dietary assessment process. ............................... 23
ix
CHAPTER 1
INTRODUCTION
There are many different types of diets. Most diets can be classified into
vegetarians and omnivorous (Craig & Mangels, 2009). Vegetarians are defined as
individuals who do not eat any meat (including fowl), poultry, fish, or products
containing these foods at all (Craig & Mangels, 2009). The food habits of vegetarians
may vary considerably. Based on their dietary intake, vegetarians may be classified as
either lacto ovo-vegetarians (LOVs) or vegans. LOVs are those who eat grains,
vegetables, fruits, legumes, seeds, nuts, dairy products, and eggs. Vegans (or total
vegetarians) are those who do not eat eggs, dairy, or other animal products. Omnivores
are people who do not have any dietary restrictions or people who include poultry,
poultry products, dairy, dairy products, fish, fish products, meat, and meat products in
their diet beside plant based foods (Craig & Mangels, 2009). Flexitarian or semivegetarians are those who eat grains, vegetables, fruits, legumes, seeds, nuts, dairy
products, and eggs on regular basis and may occasionally eat meat (Craig & Mangels,
2009).
Common reasons for choosing vegetarian diets are based on health concerns,
weight loss purposes, environmental concerns, animal welfare factors, economic reasons,
and religious reasons (Craig & Mangels, 2009; Fox & Ward, 2008; Janelle & Barr, 1995;
Smith, Burke, & Wing, 2000). Vegetarian diets may have health benefits due to intake of
low animal products, which are higher in saturated fat and cholesterol than plant products
(except palm and coconut oil). Vegetarian diets contain higher amount of photochemical
such as flavonoids, products such as fiber, and other compounds that may have health
1
benefits (Jenkins et al., 2002). Some people also choose not to eat meat and animal
products because of religious reasons such as those who follow Buddhism or Seventh
Day Adventist philosophies (Fox & Ward, 2008).
The increasing trend for college students to follow a vegetarian or semivegetarian diet indicates a need to make students and campus food services aware of the
special menus needed to ensure these students receive balanced nutritious diets. The
numbers of vegetarians in the United States (US) comprise only a small proportion of the
population, but their number is steadily increasing (McStay & Cunningham, 2009;
Stahler, 2006). Based on nationwide polls, the number of US adult population who
consistently followed a vegetarian diet increased from 2.3% in 2006 to 4% in 2012
(McStay & Cunningham, 2009; Stahler, 2006; Stahler, 2012). However, the percentage of
vegan decreased slightly from 1.4% to 0.8% (McStay & Cunningham, 2009; Stahler,
2006). This means that approximately 7.5 million people in the US are vegetarians. A
recent survey showed that 21 % of college students are vegans or vegetarians or
flexitarians as determined by limiting meat consumption, eating only certain types of
meat, or eating meat only occasionally (Techtomic, 2011).
The increased number of people consuming vegetarian diets influence
foodservices, and they responded by offering vegetarian option at all meals. Sodexo
reported that 71% of their foodservice clients in the US are offering vegetarian option at
their sites (Sodexo, 2010). A survey of chefs found that meatless entrees were considered
a “hot trend” by 62% and vegan entrees by 59% by members of the American Culinary
Federation (National Restaurant Association, 2011; National Restaurant Association,
2
2015). Additionally, the total US retail sales of vegetarian foods increased significantly
from $ 815 million in 2001 to $ 1.4 billion in 2008 (Mintel, 2007).
It is possible that one type of diet may be more adequate than other diets, if it
complies with the Dietary Reference Intakes (DRIs) (Food and Nutrition Board, Institute
of Medicine, & National Academies, 2011), Healthy Eating Index (Guenther et al., 2013),
or My Plate (United States Department of Agriculture, 2014) . Additionally, there might
be lower risks for certain chronic diseases when certain types of diets are followed.
Vegan diets combined with very low fat diets appeared to be useful for increasing the
intake of protective nutrients (antioxidant vitamins, carotenoids, and fiber) and
phytochemicals. This diet combination also minimize intake of pathogenic dietary factors
such as saturated fat and cholesterol, which are implicated in some chronic diseases
(Dewell, Weidner, Sumner, Chi, & Ornish, 2008).
It is important to look for low intakes of nutrients in certain diets, because of the
health risks that can accompany nutrient deficiencies or chronic low intake of important
nutrients in the diet, such as the risk of bone fracture due to calcium and vitamin D
deficiency (Appleby, Roddam, Allen, & Key, 2007), anemia due to iron and zinc
deficiency (Lozoff, Brittenham, Viteri, Wolf, & Urrutia, 1982), neurological symptoms
due to vitamin B12 deficiency and n-3 polyunsaturated fatty acids (PUFAs) (Janelle &
Barr, 1995; Trumbo, Schlicker, Yates, & Poos, 2002). The nutrient shortfalls for the
vegan diet are calcium, iron, zinc, vitamin B12, vitamin D, riboflavin, and n-3 PUFAs
(Alexander, Ball, & Mann, 1994; Craig, 2010; Davey, Spencer, Appleby, Allen, Knox, &
Key, 2003; Larsson & Johansson, 2002). Vegetarians have nutrient risks similar to vegan
such as iron, zinc, and vitamin B12; however they would have adequate intake of
3
calcium, vitamin D, riboflavin and n-3 PUFAs since they still consume eggs and dairy
products (Craig, 2010). Since milk is the major source of calcium, LOVs who include
milk in their diet showed similar intake to, or higher intake, than those of omnivores
(Weaver & Plawecki, 1994).
The overall purpose of this study is to evaluate the dietary intake of vegetarians
and omnivores diet in college students. The diet comparison is being conducted to
evaluate whether differences in essential vitamins and minerals exist among those
consuming a vegetarian or an omnivorous diet. Each diet group will also be compared to
DRIs to determine whether each group is receiving adequate or less than or greater than
adequate amounts of both essential nutrients and non-essential foods (saturated fat/ trans
fatty acids).
This study will provide information about diet differences on vegetarians and
omnivores in college students. This study might be able to provide information whether
or not college student diets have nutritional adequacy, fall short of adequacy or exceed
adequacy. This study might also provide valid information for college students to
increase or decrease certain nutrients in their diet as well as providing information to
student foodservice operations or campus food vendors to reduce or increase certain food
offerings that are good or high sources of essential nutrients, or decrease certain offerings
that may put students at risk for possible adverse health effects that might result from
excesses of non-essential foods such as saturated fat and trans fatty acids.
Definitions
AI. The recommended average daily intake level based on observed or experimentally
determined approximations or estimates of nutrient intake by a group (or groups) of
4
apparently healthy people that are assumed to be adequate; used when an RDA cannot be
determined (Institute of Medicine, 2006).
EAR. The average daily nutrient intake level that is estimated to meet the requirements
of half of the healthy individuals in a particular life stage and gender group (Institute of
Medicine, 2006).
Flexitarian or semi-vegetarians. Individuals who eat grains, vegetables, fruits, legumes,
seeds, nuts, dairy products, and eggs on regular basis and eat meat occasionally (Craig,
2010).
Lacto-ovo vegetarians. Individuals who eat grains, vegetables, fruits, legumes, seeds,
nuts, dairy products, and eggs (Craig, 2010).
Omnivores. Individuals who do not have any dietary restrictions or people who include
poultry, poultry products, dairy, dairy products, fish, fish products, meat, and meat
products in their diet beside plant based foods (Craig, 2010).
RDA. The average daily dietary nutrient intake level that is sufficient to meet the nutrient
requirements of nearly all (97-98 percent) healthy individuals in a particular life stage
and gender group (Institute of Medicine, 2006).
Vegans. Those who do not eat eggs, dairy, or other animal products (Craig, 2010).
Vegetarians. Individuals who do not eat any meat (including fowl), poultry, fish, or
products containing these foods at all (Craig, 2010).
Abbreviations
AI =
Adequate Intakes
ALA =
Alpha-linolenic acid
ANOVA = Analysis of Variance
5
BMD =
Bone Mineral Density
CHD =
Coronary Heart Disease
DH =
Diet History
DHA =
Docosohexanoic acid
DLW =
doubly labeled water
DRIs =
Dietary Reference Intakes
EPA =
Eicosapentanoic acid
FFQ =
Food Frequency Questionnaire
HEI =
Healthy Eating Index
LOV =
Lacto-ovo vegetarian
MDS =
Mediterranean Diet Score
n-3 PUFA = omega 3 polyunsaturated fatty acid
n-6 PUFA = omega 6 polyunsaturated fatty acid
PUFA =
Poly Unsaturated Fatty Acids
RDA =
Recommended Dietary Allowances
6
CHAPTER 2
LITERATURE REVIEW
The term “vegetarian” refers to very broad categories of different diet practices
which is described by what is omitted from the diet. The two most common ways of
defining vegetarian diets are vegan diets and vegetarian diets. Vegan diets refer to
practices which devoid of all animal foods, and vegetarian diets refer to practices which
devoid all flesh foods, but still include egg (ova) and/or dairy (lacto) products. Other
types of vegetarian diets may also include diet practices such as macrobiotic, raw foods,
and fruitarian diets. The macrobiotic diet is based largely on grains, legumes, and
vegetables, while fruits, nuts, and seeds are less consumed. Some people following a
macrobiotic diet still eat limited amounts of fish. A raw foods diet consists mainly of
uncooked and unprocessed foods. The foods used include fruits, vegetables, nuts, seeds,
and sprouted grains and beans, and may contain raw animal products and flesh. Fruitarian
diet is a vegan diet based on fruits, nuts, and seeds. Other vegetables, grains, beans, and
animal products are excluded. Some people will consider themselves as vegetarian but
still eat fish, chicken, or even meat occasionally. These types of diet may be identified as
semi-vegetarians or flexitarian (Craig, 2010).
Several common reasons for adopting vegetarian diets are based on health
concern, weight loss purposes, environmental concerns, animal welfare factors, economic
reasons, and also religious reasons (Craig & Mangels, 2009; Fox & Ward, 2008; Janelle
& Barr, 1995; Smith, Burke, & Wing, 2000). In Western countries, the major motivation
for choosing vegetarian diets is for health reasons. Some believe that it lower the risks of
foodborne diseases that are common in unhygienic preparation of animal products
7
(Dwyer, 2003). Animal products also contain higher saturated fat and cholesterol than
plant products. Others also choose vegetarian diets because of the phytochemicals content
in plants that may have health benefits (Fox & Ward, 2008).
Dietary Intakes
Vegetarians have nutrient risks like iron, zinc, and vitamin B12; however they
may have adequate intake of calcium, vitamin D, riboflavin and n-3 PUFAs since they
still consume eggs and dairy products (Craig, 2010). Since milk is the major source of
calcium, LOVs who include milk in their diet showed similar intake to, or higher intake,
than those of omnivores (Weaver & Plawecki, 1994).
Energy
Vegans tend to have lower energy intakes and lower Body Mass Index (BMI)
than omnivores or other vegetarians (Alexander, Ball, & Mann, 1994; Larsson &
Johansson, 2002; McStay & Cunningham, 2009; Smith, Burke, & Wing, 2000; Tonstad,
Butler, Yan, & Fraser, 2009). The differences are less consistent, especially among those
who adopt other vegetarian patterns. In one study between health conscious omnivores
and vegetarians, there was no difference in the observed energy intake (Janelle & Barr,
1995). Vegans tend to have lower intakes of calorie, protein, saturated fat, and cholesterol
than those of omnivores. Research indicated that vegetarians were at lower risk of death
from ischemic heart disease than omnivores (Key et al., 1999). This lower risk was seen
in both LOVs and vegans. Even after adjustment for BMI, the difference in risk still
persisted, suggesting that lower BMI in vegetarians might be one factor that influences
this risk.
8
Carbohydrate
Intakes of carbohydrates, especially complex carbohydrates and dietary fiber, tend
to be higher in vegetarians than omnivores (Janelle & Barr, 1995; Smith, Burke, & Wing,
2000). Vegetarians consume between 50% and 100% more fiber than omnivores. Vegans
have higher intakes of fiber than LOVs. In one meta-analysis study, among the sources of
dietary fiber, consumption of cereals and fruits was inversely associated with risk of
CHD, but not for vegetable fiber (Pereira et al., 2004).
Protein
Vegetarians usually have a lower intake of total protein than omnivores. Although
the intakes of vegan women were marginal, but the intakes of vegans and LOVs usually
meet the requirement of protein recommendation (Alexander, Ball, & Mann, 1994;
Larsson & Johansson, 2002; McStay & Cunningham, 2009; Smith, Burke, & Wing,
2000; Tonstad, Butler, Yan, & Fraser, 2009). The differences between plant and animal
products are due to the different concentrations of proteins and essential amino acids. In
some plant foods, the protein concentration and quality may be too low to be sole sources
of proteins. For example, soy protein is low in sulfur-containing amino acids; however,
cottonseed, peanut, and grains are deficient mainly in lysine. A combination of soy
protein, which is high in lysine, with grains that contains good amount of sulfurcontaining amino acids can results in a nutritional complementation (Young & Pellett,
1994). Studies indicated that complementary proteins in plant foods in appropriate
amounts are able to supply adequate protein for maintenance of health and function. The
complementary proteins do not need to be consumed at the same time, eating it over the
course of a day can provide all essential amino acids (Young & Pellett, 1994).
9
Fat and Saturated Fat
Most vegetarian diets are lower in fat, saturated fat, and cholesterol, and higher in
polyunsaturated and monounsaturated fats than omnivore diets are. In one of a cohort
study (Davey, Spencer, Appleby, Allen, Knox, & Key, 2003), the percentage of energy
from saturated fat was significantly different across the four diet groups (vegans, LOVs,
fish-eaters, and meat-eaters). Vegans had less saturated fat intake than half the mean
intake of meat-eaters. The levels of saturated fatty acids are directly correlated with CHD
(Simon, Hodgkins, Browner, Neuhaus, Bernert, & Hulley, 1995).
n-3 PUFAs
Vegetarian diets are generally rich in n-6 PUFAs, but low in n-3 PUFAs. N-3
PUFAs are essential fatty acids since it cannot be synthesized endogenously and must be
provided in the diet (Food and Nutrition Board & Institute of Medicine, 2005). The major
sources of n-3 PUFAs include seafood, meat, and eggs (Meyer, Mann, Lewis, Milligan,
Sinclair, & Howe, 2003). Consequently, vegetarians, who do not eat meat or fish, and
vegans, who also do not eat animal products at all, might have very low or negligible
intakes of eicosapentaenoid acid (EPA) and docosahexanoic acid (DHA). EPA and DHA
are n-3 PUFAs important for cardiovascular health as well as eye and brain development.
Although EPA and DHA can be synthesized in the body from α-linolenic acid, which is
largely available in plant-based foods, the conversions to EPA is limited (less than 10%).
The conversion to DHA is substantially less than the conversion to EPA from α-linolenic
acid (Rosell, Lloyd-Wright, Appleby, Sanders, Allen, & Key, 2005).
Vegetarians, especially vegans tend to have lower blood levels of EPA and DHA
than omnivores. The duration of adherence to vegetarian or vegan diet did not
10
significantly affect the proportions of plasma long chain n-3 PUFAs. It suggests that
when animal foods are excluded totally from the diet, the endogenous production of EPA
and DHA results in low but stable plasma concentrations of these fatty acids. N-3 PUFAs
are also associated with lower risk of developing CHD (Simon, Hodgkins, Browner,
Neuhaus, Bernert, & Hulley, 1995). DHA supplements derived from microalgae are well
absorbed and positively influence blood levels of DHA and EPA through retroconversion
(Rosell, Lloyd-Wright, Appleby, Sanders, Allen, & Key, 2005).
Iron
The iron intake of vegetarians is usually similar to omnivores. However, the
bioavailability of iron in plants is lower than from animal products because iron
absorption is influenced by other substances which are contained in plants, such as
polyphenols, phytates, fiber, and tannins (Dwyer, 2003).The differences in the chemical
form of iron from plant which is nonheme iron also influence the iron absorption (Hunt,
2003) . The elimination of meat may be accompanied by an increased consumption of
beans and legumes, fruit and vegetables, and whole grain. Such diet choices can enhance
or inhibit the intestinal efficiency in the absorption of nonheme iron.
Vitamin C and other organic acids found in fruits and vegetables can enhance iron
absorption and reduce the effect of phytate. Ascorbic acid forms an easily absorbable
chelate consisting of ascorbic acid and ferric iron. It also prevents the formation of
insoluble and unabsorbable iron compounds between nonheme iron and inhibitors
(Hallberg, Brune, & Rossander, 1989). Therefore, the efficiency of nonheme iron
absorption is dependent on the enhancing and inhibiting food substances being consumed
concurrently. The lower availability of iron from plant-based food resulted in the
11
recommendation of iron intakes for vegetarians as 1.8 times as those of omnivores (Food
and Nutrition Board & Institute of Medicine, 2001). Iron deficiency will cause anemia
which can further impair work performance and cognitive process; however, low intakes
of iron over a long term period will lead to adaptation where the iron absorption will
increase and iron losses will decrease (Hunt & Roughead, 2000). Furthermore, incidence
of iron deficiency anemia is similar to that of omnivores. The vegetarian adults have
normal serum ferritin levels, which indicate that their iron status is within the normal
range (Alexander, Ball, & Mann, 1994).
Calcium
Foods that contain substantial amounts of calcium include dairy products,
calcium-set tofu, some roots and legumes, some green vegetables, calcium-fortified fruit
drinks, and calcium-fortified soy milk (Weaver & Plawecki, 1994). Calcium absorption is
considerably reduced by oxalates and phytates, which are found in plant sources. Oxalate
can bind ionized calcium and decrease its absorption. Diets high in fat may decrease
calcium absorption by forming unabsorbable calcium soaps. These soaps are ionically
formed between the acid portion of a fatty acid and calcium (Medeiros & Wildman,
2011). Since milk is the major source of calcium, LOVs who include milk in their diet,
showed similar intake to, or higher intake than those of omnivores (Weaver & Plawecki,
1994). A large cohort study showed that vegans have a considerably lower mean calcium
intake than nonvegans (Davey, Spencer, Appleby, Allen, Knox, & Key, 2003). Some
studies also showed that vegans had considerably lower intakes than recommended
intakes of calcium (Janelle & Barr, 1995; Larsson & Johansson, 2002). Diet rich in meat,
dairy products, nuts, and grains produces a high renal acid load. Calcium resorption from
12
bone helps to buffer this acid load, led to increased loss of calcium. A high sodium intake
also promotes urinary calcium losses. On the other hand, potassium and magnesium rich
diet produce high renal alkaline load which slow bone calcium resorption and decrease
the calcium losses in urine (Craig & Mangels, 2009).
Calcium is considered one of the factors known to influence bone health and
fracture risk. The risk of bone fracture between LOVs and omnivores were not
significantly different, whereas vegans had a 30% higher risk of fracture possibly because
of their considerably low mean calcium intake (Appleby, Roddam, Allen, & Key, 2007).
Another meta-analysis study showed that bone mineral density (BMD) was 4% lower in
vegetarians as compared to non-vegetarians. The fracture risk was 10% greater for
vegetarians but the risk was clinically insignificant (Ho-Pham, Nguyen, & Nguyen,
2009).
Vitamin D
A cohort study showed progressive decreases in dietary vitamin D intakes from
omnivores, through fish eaters, and vegetarians to vegans (Davey, Spencer, Appleby,
Allen, Knox, & Key, 2003). Vegan and macrobiotic groups who did not take vitamin D
supplements or fortified foods had low vitamin D intakes (Janelle & Barr, 1995; Larsson
& Johansson, 2002), low serum 25-dehydroxyvitamin D levels (Janelle & Barr, 1995),
and reduced bone mass (Parsons, van Dusseldorp, van der Vliet, van de Werken,
Schaafsma, & van Staveren, 1997). The rate of bone mineral formation reaches its
maximum state during adolescence, and peak bone mass subsequently attained is
considered as one of the major determinant of fracture risk in later life (Parsons, van
Dusseldorp, van der Vliet, van de Werken, Schaafsma, & van Staveren, 1997).
13
The major source of vitamin D is from exposure of the skin to sunlight (Holick,
1994). Only a few foods contain vitamin D, which are fish liver oils, fatty fish, liver, and
eggs. Other sources are fortified foods like cereals and milk (Lips, Graafmans, Ooms,
Bezemer, & Bouter, 1996). If sun exposure and fortified foods are insufficient to meet
needs, vitamin D supplements are needed. Although vitamin D is also recognized as
importance for bone health, dietary vitamin D is a poor indicator of vitamin D status
because vitamin D production is mostly from endogenous vitamin D formation from
exposure to sunlight, which varies (Appleby, Roddam, Allen, & Key, 2007).
Vitamin B12
Vitamin B12 is naturally present exclusively in animal products. Therefore,
individuals who do not have intake from animal products at all like vegans are likely to
develop vitamin B12 deficiency. Study in young Swedes (Larsson & Johansson, 2002),
showed vitamin B12 intake from vegans which was lower than the average requirement.
In the same study, although one of the vegan participants took B12 supplements, the
nutritional status was still lower than normal, indicating a failure in absorption rather than
low intake. LOVs can obtain adequate vitamin B12 from dairy foods, eggs, or other
reliable vitamin B12 such as fortified foods and supplements if regularly consumed;
however, one study showed that even LOV did not meet the vitamin B12 requirement
from diet alone (Janelle & Barr, 1995). Vegetarian diets are usually rich in folate, with
vegan diet as the highest intake of folate. High level of folate may mask the symptoms of
vitamin B12 deficiency until it reaches neurological symptoms (Gilsing et al., 2010).
14
Table 1
A Summary of Vegetarian Studies from Literature Review
Study Investigators
(Date, Journal)
Clarys et al.
2013
Nutrition Journal
(Clarys,
Deriemaeker,
Huybrechts,
Hebbelinck, &
Mullie, 2013)
Objective
Methodology
Results
Compare dietary
intake using two
different dietary
pattern analyses in
matched vegetarian
and omnivorous
participants.
n = 69 vegetarians
matched with n= 69
omnivores, 3 days
food diaries were
analyzed with
BECEL software.
HEI and MDS score
diet adequacy.
Vegetarians had ↓
intakes in protein,
total fat, saturated,
monounsaturated,
and cholesterol; and
↑ carbohydrate
intake. Fiber intake
≈2x in vegetarians.
The HEI-2010 score
and MDS score ↑ in
vegetarians,
indicating more
favorable diet.
Davey et al.
2002
Public Health
Nutrition
(Davey, Spencer,
Appleby, Allen,
Knox, & Key,
2003)
Describe the
lifestyle
characteristics and
nutrient intakes of
the European
Prospective
Investigation into
Cancer and
Nutrition (EPIC)
Oxford cohort.
n= 65,429 men and
women, 20-97 years
of age. n= 33,883
meat-eaters, n=
10,110 fish-eaters,
n=18,840 LOVs,
and n=2,596
vegans.
Assessment:
anthropometrics +
lifestyle
characteristics using
7 day food diaries
and FFQ.
Energy intakes=
14% ↓ in vegans
than to meat-eaters.
Carbohydrate &
fiber intakes=
highest in vegans &
lowest in meateaters. Protein & fat
intakes= highest in
meat-eaters and
lowest in vegans.
Vegans had the
highest intakes in
vitamin B1, folate,
vitamin C, vitamin
E, magnesium, and
iron; and the lowest
intakes of vitamin
B2, niacin, vitamin
B6, calcium, and
zinc. The fish-eater
and LOVs values
were intermediate
between groups.
15
Table 1
A Summary of Vegetarian Studies from Literature Review (continued)
Study Investigators
(Date, Journal)
Gilsing et al.
2010
European Journal
of Clinical
Nutrition
(Gilsing et al.,
2010)
Objective
Methodology
Results
Compare the
vitamin B12 and
folate status
between omnivores,
vegetarians, and
vegans, and to
ascertain whether
vitamin B12
concentrations
differed between
age and time on the
diet.
n = 689 men (226
omnivores, 231
vegetarians, and 232
vegans) from the
EPIC Oxford
cohort.
Serum vitamin B12=
highest in omnivores
 vegetarians 
vegans. 52% vegans,
7% vegetarians, 1%
omnivores were
deficient in vit. B12.
No significant
association between
age or time on the
diet with vitamin
B12.
Folate = highest in
vegan, intermediate
in vegetarians, &
lowest in omnivores.
2 men in omnivores
were folate
deficient.
Knurick et al.
2015
Nutrients
(Knurick, Johnston,
Wherry, & Aguayo,
2015)
Compare
correlations between
indicators of bone
health and bone
mineral density
(BMD) in meat
based, LOV, and
vegan diet.
n = 27 meat based, n
= 27 LOV, and n =
28 vegan. A 24 h
diet recall, 24 h
urine specimen, and
fasting blood
sample were
collected.
BMD did not differ
significantly
between groups
(4%-5% reduction in
LOVs and vegans).
LOVs and vegans
consumed
~30% less protein
than meat based diet.
Vegans consumed
more Mg, folate, and
vit K. Vit B12
intakes were
significantly reduced
in vegetarian diets.
Data suggested that
plant-based diets
were not detrimental
to bone health in
young adults.
16
Table 1
A Summary of Vegetarian Studies from Literature Review (continued)
Study Investigators
(Date, Journal)
Lockie et al.
1985
Journal of the
Royal College of
General
Practitioners
(Lockie, Carlson,
Kipps, & Thomson,
1985)
Objective
Methodology
Results
Compare vegans,
LOVs, whole-food
omnivores, and
average omnivores
dietary habits suing
clinical, laboratory,
and psychological
studies.
n=10 in each group
(5 males & 5
females), 3 were
removed later.
9 days food records,
psychological
assessments using
health
questionnaire, &
nutrient status.
Vegan group had ↓
energy intakes than
the RDA, the lowest
fat intake level,
dietary cholesterol,
& highest
carbohydrate intake.
Vegans were
deficient in vitamin
D, riboflavin, and
vitamin B12. All
groups were low in
folic acid, with the
average omnivore
groups being the
lowest.
Rizzo et al.
2013
Journal of the
Academy of
Nutrition and
Dietetics
(Rizzo, JaceldoSiegl, Sabate, &
Fraser, 2013)
Compare dietary
intakes between non
vegetarian, semivegetarian,
pescovegetarian,
LOV, and vegan.
n = 71,751 from the
Adventist Health
Study 2. Mean age=
59 y.o. Dietary
intakes assessment:
semi-quantitative
FFQ. Nutrient
differences between
dietary patterns
were analyzed using
ANOVA and chi
square test.
Non vegetarians had
the lowest intakes of
proteins, fiber, beta
carotene, &
magnesium; and the
highest intakes of
saturated, trans,
arachidonic, and
DHA fatty acids.
Vegetarians had
inadequate intakes
of some nutrient
distributions. Mean
BMI is highest in
non vegetarians and
the lowest in vegans.
17
Table 1
A Summary of Vegetarian Studies from Literature Review (continued)
Study Investigators
(Date, Journal)
Schupbach et.al
2015
European Journal
of Nutrition
(Schupbach,
Wegmuller,
Berguerand, Bui,
& Herter-Aeberli,
2015)
Objective
Methodology
Results
Assess dietary
intake and status of
vitamins and
minerals between
vegetarian and
vegan adults in
Switzerland.
n = 100 omnivores,
n= 53 vegetarians,
and n = 53 vegans.
Mean age = 18 – 50
y.o. 3 days dietary
intake and nutrition
status assessment.
Omnivores had the
lowest intake of Mg,
vit C, vit E, niacin,
and folic acid.
Vegans had low
intakes of Ca and
low marginal
intakes of vit D and
B12. 58% of
omnivores had folic
acid deficiencies,
58% and 34% of
vegetarians had
vitamin B6 and
niacin deficiencies,
and 47% of vegans
group had Zn
deficiency. Iron
deficient was
comparable across
all diet groups.
Vegans had
adequate status of
vit B12 due to
widespread use of
supplements.
Welch et.al.
2010
The American
Journal of Clinical
Nutrition
(Welch, ShakyaShrestha, Lentjes,
Wareham, &
Khaw, 2010)
Compare the n-3
PUFAs intakes,
food sources, and
nutritional status
between fish-eaters,
non-fish eating
meat-eaters,
vegetarian, and
vegan.
n=14,422 from the
EPIC Norfolk
cohort. Mean age=
39-78 y.o.
7 days diary data
with intakes and
status of n-3
PUFAs were
measured.
Non-fish eaters had
↓ n-3 PUFA intakes
(57-80%) than fish
eaters. The n-3
PUFA status
between the groups
were insignificant.
The estimated
precursor-product
ratio was greater in
non-fish eaters than
fish eaters.
18
Statement of Problem
There are considerable amount of studies done on vegetarians; however, study
that targets college students have not been done.
Statement of Purpose
The purpose of this study is to assess the dietary intake of vegetarians and
omnivores diet in college students by comparing the energy and nutrient intake of each
diet group to each other and assessing whether each diet group meets the Dietary
Reference Intakes of America.
Hypotheses
Null Hypotheses
1. There will be no significant difference of energy intake between vegetarians and
omnivores
2. There will be no significant difference of nutrient intakes between vegetarians and
omnivores.
3. Each diet group will meet the nutrient recommendation of Dietary References
Intakes (DRIs).
Alternative Hypotheses
1. There will be significant difference of energy intake between vegetarians and
omnivores.
2. There will be significant difference of nutrient intake between vegetarians and
omnivores.
3. Each diet group will not meet the nutrient recommendation of DRIs
19
Significance of the study
This study is a preliminary study on diet information of college students in the
US. This can be used as the baseline data on nutrient intake in two different eating habits
for further research question pertaining to college students.
Assumptions
Since the data is based on self-reporting food-record, it is assumed that
participants recorded the actual food intakes in detail.
20
CHAPTER 3
METHODS
Participants
This study is a self- reported study that evaluates nutrient intake in vegetarian and
omnivorous diets. The study was performed at California State Polytechnic (Cal Poly)
University Pomona and Loma Linda University. The Cal Poly Pomona Institutional
Review Board and Loma Linda University Institutional Review Board approved the
study protocol (IRB protocol # 11-138; Appendix A) and all participants provided written
informed consent (Appendix B). Approximately 30-35 students for each diet group
(vegetarian and omnivore) were to be invited to participate (total n= 60-75). The power to
test the difference of the diet groups from a sample size of 30 for each group is 93%
(Tukey/HSD test) (Lenth, 2007).
Recruitment
Participants were a convenience sample of healthy Cal Poly Pomona and Loma
Linda University students. Participants were recruited in the beginning of February 2011
until December 2014 via emails, presentation, and flyers on Cal Poly Pomona campus
and Loma Linda University. With the permission of the teaching professor, a 5-minute
recruitment presentation explaining the study was made to each class. The students in
online classes were emailed the recruitment advertisement along with the consent form
by the researcher with permission of the teaching professor. Students who wished to
participate were given a consent form, and after they signed the consent form, they were
given a screening questionnaire about their diet (Appendix C). The researcher also sent
out mass emails. In the emails, the researcher explained what the study was about and the
21
criteria to participate in this study. Some recruitment was also accomplished by the word
of mouth, in which participants were asked to speak with acquaintances about the study.
The inclusion criteria for this study were participants had to be healthy, between
the ages of 18 and 35 years, not pregnant or lactating. Pregnant or lactating women were
not included in the study, since this was a temporary condition requiring additional
nutrients and calories that could potentially skew and bias the study results.
Dietary Assessment
After the participants signed the consent form and filled out the screening
questionnaire, five randomized day food and activity records were given for them to
complete (Appendix D). In the screening questionnaire, participants answered the
questions given about their habitual diet (what diet are they considering themselves
practicing, age, gender, how often they eat meat and fish, how often do they eat dairy,
and what type of supplements they take) (See Appendix C). Their physical activity level
was also asked, since it may relate to the amount of food they consumed. The answers to
the screening questions were reviewed and were compared with the actual food records to
determine whether they fit into vegetarian and omnivorous diets. LOV individuals are
defined as those who eat only plants, eggs, dairy, egg products, and dairy products.
Vegan individuals are defined as those who eat only plants and plant products.
Omnivorous individuals are defined as those who eat plants, eggs, dairy, meat, and meat
products. The participants then submitted five day food and physical activity records.
The five days for which the participants kept the food records were randomized
by the researcher using a random number generator for each diet group (Graphpad
Software Inc., 2005). The five day food and physical activity records were completed
22
within 90 days. After filling out the diet and exercise log, the participant emailed or gave
the form back to the researcher.
The nutritional composition of each food was determined using the Food
Processor Nutrition and Fitness software (ESHA Research, 2010). The amount of
nutrients in each diet group were calculated and averaged, and then compared to nutrient
recommendations by Dietary Reference Intakes (DRIs) (Food and Nutrition Board,
Institute of Medicine, & National Academies, 2011). The mean of the energy and nutrient
intakes were also used for comparison for two different diet groups that were being
studied. Figure 1 shows the recruitment and dietary assessment procedures for each
participant.
Figure 1. Flowchart of recruitment and dietary assessment process.
Limitations and Delimitations
Since the data was based on self-reporting food-records, it was assumed that
participants recorded the actual food intakes in sufficient detail and accuracy. However,
there may have been some bias in the measurement of the diet. Study indicates that there
is a significant decrease in validity of the collected information in the fifth and later days
23
of a seven day recording period in contrast to collected information in the earlier days
(Gersovitz, Madden, & Smiciklas-Wright, 1978). To reduce the fatigue of recording
dietary records continuously, the five days of which participants need to do the food
records were randomized and participants were asked to only do the food record one day
at a time. Participants were also given directions on how to do the food and activity
record to minimize inaccuracy in recording their diet and activities. The directions
included how to record each food by estimating the serving size of the food, reading the
labels of the foods they consume, including the name brand or the food name if
applicable. Contact and review of the food record after one day of recording was made to
clarify entries and to probe for forgotten foods.
Another limitation of this study was that actual nutritional status analyses might
have been required to confirm the effect of nutrient intake on nutritional status in the
body. However, due to time and cost, the data on nutrients collected from participants
was compared with the assumption that nutrient intake reflected the nutritional status in
the body. The results were also compared with data that were available in the research
journals. There may have been a chance that the sample of students might not reflect the
actual population of college students because the majority of samples were from the
College of Agriculture, and there were an uneven ratio between female and male
participants.
Statistical Analysis
Statistical information was obtained using SPSS for WINDOWS (version 22;
SPSS Inc., Chicago, IL, USA). Data were reported as mean ± SD. A p value of ≤ 0.05was
considered statistically significant. The first objective of this study was to compare the
24
energy intake of each diet group to the other diet group using independent-samples T-test.
The second objective of this study was to compare the nutrient intake of each diet group
to each other using independent-samples T-test. The nutrients that were evaluated were
all nutrients that are recommended by DRIs. The third objective of this study was to
compare the nutrient value to the DRI requirements (RDA, AI, and EAR) using Student’s
t-test.
25
CHAPTER 4
RESULTS
A total of 74 participants signed the consent forms and completed the screening
questionnaires. The five day food and activity records were returned by 33 participants.
Based on self-reported diet habits, participants were grouped into two diet groups,
vegetarian (n = 12) and omnivore (n = 21). Participants in the vegetarian group were all
female. Participants in the omnivore group were 2 males and 19 females. Age, body
weight, height, and BMI did not differ significantly between vegetarians and omnivores.
Table 2 shows the characteristics of the study population by diet group.
Table 2
Participant characteristics by diet group
Omnivore
Vegetarian
Mean ± SD
Mean ± SD
Gender, M/F
2/19
0/12
Age (year)
23.3 ± 3.08
25.1 ± 5.27
Body weight (lb)
133 ± 23.4
132 ± 26.9
Height (inch)
58.6 ± 3.08
64.2 ± 2.63
2
BMI (lb/inch )
23.3 ± 3.85
22.5 ± 4.46
The data are expressed as mean ± SD (standard deviation)
p-value
0.286
0.937
0.345
0.604
Results from the five days of food records were averaged for each participant and
were used for group comparisons, as shown in Table 3 mean total energy intake was
comparable between vegetarian and omnivorous participants (p > 0.05). Protein,
saturated fat, cholesterol, selenium, and sodium intakes were significantly lower for the
vegetarians compared to the omnivore participants. Fiber, soluble fiber, vitamin A, folate,
vitamin K, copper, magnesium, and selenium intakes were significantly higher for the
vegetarians compared to the omnivore participants.
26
Table 3
Dietary intake (including supplements) analysis between omnivore and vegetarian
groups
Diet
Calories (kcal)
Calories from Fat (kcal)
Calories from Saturated
Fat (kcal)
Protein (g)
Carbohydrates (g)
Total Fiber (g)
Soluble Fiber (g)
Total Sugars (g)
Monosaccharide (g)
Disaccharides (g)
Other Carbohydrate (g)
Fat (g)
Saturated Fat (g)
Mono Fat (g)
Poly Fat (g)
Trans Fatty Acid (g)
Cholesterol (mg)
Vitamin A-IU (IU)
Vitamin A-RAE (RAE)
Carotenoid RE (RE)
Retinol RE (RE)
Bet-Carotene (mcg)
Vitamin B1 (mg)
Vitamin B2 (mg)
Vitamin B3 (mg)
Vitamin B3-NE (mg)
Vitamin B6 (mg)
Vitamin B12 (mcg)
Biotin (mcg)
Vitamin C (mg)
Vitamin D-IU (IU)
Vitamin D-mcg (mcg)
Vitamin E-AlphaTocopherol (mcg)
Folate (mcg)
Omnivore
(n=21)
Mean ± SD
1717 ± 401
540 ± 144
164 ± 56.6
Vegetarian
(n=12)
Mean ± SD
1525 ± 405
472 ± 145
122 ± 41.1
t
df
pvalue
-1.32
-1.30
-2.23
31.0
31.0
31.0
0.198
0.204
0.033
76.9 ± 20.4
219 ± 57.2
18.7 ± 6.48
0.96 ± 0.70
75.2 ± 37.6
5.65 ± 5.86
7.62 ± 7.80
102 ± 29.7
60.2 ± 16.1
18.2 ± 6.29
10.7 ± 6.32
4.89 ± 2.36
0.62 ± 0.54
233 ± 164
7555 ± 4161
404 ± 229
569 ± 391
119 ± 93.2
2425 ± 1943
2.71 ± 8.76
2.90 ± 9.24
10.9 ± 8.50
17.6 ± 17.6
3.07 ± 9.31
5.34 ± 10.1
15.0 ± 33.4
162 ± 221
102 ± 97.3
2.10 ± 1.48
4.50 ± 6.01
52.4 ± 18.1
221 ± 85.3
29.3 ± 14.9
2.38 ± 1.68
77.9 ± 33.1
10.7 ± 9.96
6.16 ± 6.19
90.6 ± 47.4
52.7 ± 16.3
13.6 ± 4.57
11.8 ± 6.79
6.99 ± 4.48
0.34 ± 0.45
92.3 ± 92.6
12650 ± 6816
653 ± 283
1104 ± 641
102 ± 207
5334 ± 3947
1.00 ± 0.89
0.88 ± 0.55
8.02 ± 7.04
11.2 ± 7.99
1.15 ± 0.83
18.1 ± 57.9
184 ± 574
126 ± 98.8
72.6 ± 117
1.77 ± 2.95
9.74 ± 13.2
-3.44
0.05
2.34
2.80
0.21
1.85
-0.56
-0.85
-1.29
-2.23
0.48
1.50
-1.56
-2.72
2.35
2.75
2.63
-0.33
2.39
-0.67
-0.75
-1.00
-1.20
-0.71
0.76
1.02
-0.53
-0.80
-0.43
1.57
31.0
31.0
13.4
13.2
31.0
31.0
31.0
31.0
31.0
31.0
31.0
14.6
31.0
31.0
15.8
31.0
15.8
31.0
14.1
31.0
31.0
31.0
31.0
31.0
11.4
11.0
31.0
31.0
31.0
31.0
0.002
0.961
0.035
0.015
0.835
0.073
0.582
0.404
0.207
0.033
0.632
0.154
0.130
0.011
0.032
0.010
0.018
0.746
0.031
0.508
0.459
0.327
0.239
0.484
0.464
0.330
0.599
0.432
0.667
0.127
138 ± 71.8
300 ± 184
2.92
13.0
0.012
27
Table 3
Dietary intake (including supplements) analysis between omnivore vegetarian groups
(continued)
Omnivore
Vegetarian
(n=21)
(n=12)
Diet
Mean ± SD
Mean ± SD
Vitamin K (mcg)
40.6 ± 47.1
198 ± 159
Pantothenic Acid (mg)
3.83 ± 9.17
2.91 ± 2.96
Calcium (mg)
640 ± 222
720 ± 281
Chromium (mcg)
3.47 ± 6.52
4.31 ± 7.18
Copper (mg)
0.53 ± 0.34
0.86 ± 0.51
Fluoride (mg)
0.24 ± 0.41
0.21 ± 0.24
Iodine (mcg)
18.3 ± 26.5
13.7 ± 11.7
Iron (mg)
11.1 ± 3.17
16.0 ± 12.6
Magnesium (mg)
127 ± 64.6
209 ± 131
Manganese (mg)
1.48 ± 0.95
2.77 ± 2.19
Molybdenum (mcg)
8.33 ± 7.78
22.0 ± 21.5
Phosphorus (mg)
507 ± 222
511 ± 285
Potassium (mg)
1358 ± 660
1677 ± 985
Selenium (mcg)
42.1 ± 22.1
27.2 ± 11.3
Sodium (mg)
2944 ± 932
1747 ± 694
Zinc (mg)
6.03 ± 4.18
5.42 ± 4.49
n- 3 PUFA (g)
0.45 ± 0.28
0.42 ± 0.28
n- 6 PUFA (g)
8.59 ± 26.7
3.19 ± 1.74
Alcohol (g)
0.78 ± 3.38
0.31 ± 1.08
Caffeine (mg)
91.6 ± 173
62.1 ± 94.2
Choline (mg)
103 ± 55.6
92.6 ± 47.5
The data are expressed as mean ± SD (standard deviation)
t
df
pvalue
3.34
-0.33
0.91
0.34
2.21
-0.20
-0.56
1.32
2.43
1.93
2.04
0.04
1.11
-2.16
-3.87
-0.39
-0.28
-0.70
-0.46
-0.54
-0.56
12.1
31.0
31.0
31.0
31.0
31.0
31.0
11.8
31.0
13.4
11.5
31.0
31.0
31.0
31.0
31.0
31.0
31.0
31.0
31.0
31.0
0.006
0.742
0.369
0.735
0.035
0.843
0.580
0.212
0.021
0.075
0.065
0.966
0.274
0.038
0.001
0.698
0.782
0.492
0.649
0.591
0.581
The data of two male omnivorous participants was removed since there was no
male participant in the vegetarian group. The mean nutrient intakes of each diet groups
(19 females omnivores and 14 females vegetarian) then was compared again (Table 4
and Table 5). Each nutrient value was compared to Dietary Reference Intakes (DRIs) of
females in 19-40 years old life stage (Table 6). Nutrients that were compared were the
macronutrients, along with nutrients of concern in the vegetarian diets: vitamin B12,
vitamin D, riboflavin, calcium, iron, and zinc (Alexander, Ball, & Mann, 1994; Craig,
28
2010). The DRIs are reference values that are quantitative estimates of nutrient intakes to
be used for planning and assessing diets for healthy people (Institute of Medicine, 2006).
The reference values include the Estimated Average Requirement (EAR), Recommended
Dietary Allowance (RDA), the Adequate Intake (AI), the Tolerable Upper Intake Level
(UL), the Estimated Energy Requirement (EER), and the Acceptable Macronutrient
Distribution Range (AMDR). RDA and AI were commonly used in studies to measure
the nutrient adequacy in individuals. EAR was used to measure the nutrient adequacy in a
diet group (Institute of Medicine, 2006).
Table 4
Macronutrient intake (including supplement) between female vegetarians and female
omnivores
Omnivore
Vegetarian
(n
=
19)
(n=12)
Diet
Mean ± SD Mean ± SD
Calories (kcal)
1687 ± 403
1525 ± 405
Protein (g)
74.1 ± 19.1
52.4 ± 18.1
Carbohydrates (g)
220 ± 60.3
221 ± 85.3
Dietary Fiber (g)
19.0 ± 6.74
29.3 ± 14.9
Fat (g)
58.4 ± 15.1
52.7 ± 16.3
Saturated Fatty Acids (g) 17.7 ± 5.81
13.6 ± 4.57
Monounsaturated fat (g)
9.77 ± 5.50
11.8 ± 6.79
Polyunsaturated fat (g)
4.68 ± 2.27
6.99 ± 4.48
n- 3 PUFA (g)
0.46 ± 0.30
0.42 ± 0.28
n- 6 PUFA (g)
2.71 ± 1.37
3.19 ± 1.74
Trans Fatty Acid (g)
0.57 ± 0.51
0.34 ± 0.45
Cholesterol (mg)
233 ± 173
92.3 ± 92.6
Alcohol (g)
0.04 ± 0.11
0.31 ± 1.08
The data are expressed as mean ± SD (standard deviation)
t
df
p-value
-1.08
-3.14
0.04
2.27
-0.99
-2.07
.931
1.66
-0.41
-0.86
-1.28
-2.59
0.87
29.0
29.0
29.0
13.8
29.0
29.0
29.0
14.6
29.0
29.0
29.0
29.0
11.2
.287
.004
.970
.040
.330
.047
.359
.119
.688
.398
.210
.015
.404
Mean calories intake did not differ between vegetarian and omnivore participants
(p > 0.05) (Table 4). Macronutrient intake analysis showed no significant differences
between carbohydrate intake, total fat intake, n-3 PUFA, n-6 PUFA, and trans fatty acid
of vegetarian and the omnivore participants. Omnivore participants had significantly
29
higher protein, saturated fatty acids and cholesterol intakes; also significantly lower
dietary fiber intake.
Table 5
Dietary intake of vitamins and minerals (including supplement) between female
vegetarians and female omnivores
Diet
Omnivore
(n = 19)
Mean ± SD
417 ± 237
2555 ± 1998
2.92 ± 9.21
3.13 ± 9.71
17.7 ± 18.5
Vegetarian
(n=12)
Mean ± SD
653 ± 283
5334 ± 3947
1.00 ± 0.89
0.88 ± 0.55
11.2 ± 7.99
Vitamin A-RAE (RAE)
Beta-Carotene (mcg)
Vitamin B1 (mg)
Vitamin B2 (mg)
Vitamin B3-Niacin
Equivalent (mg)
Vitamin B6 (mg)
3.29 ± 9.78
1.15 ± 0.83
Vitamin B12 (mcg)
5.49 ± 10.6
18.1 ± 57.9
Biotin (mcg)
16.1 ± 35.0
183 ± 574
Vitamin C (mg)
169 ± 232
126 ± 98.8
Vitamin D-mcg (mcg)
2.18 ± 1.50
1.77 ± 2.95
Folate, DFE (mcg)
149 ± 106
299 ± 253
Vitamin K (mcg)
43.7 ± 48.5
198 ± 159
Calcium (mg)
645 ± 231
720 ± 281
Chromium (mcg)
3.58 ± 6.85
4.31 ± 7.18
Copper (mg)
0.54 ± 0.35
0.86 ± 0.51
Iron (mg)
11.2 ± 3.33
16.0 ± 12.6
Magnesium (mg)
125 ± 64.8
210 ± 131
Manganese (mg)
1.46 ± 0.93
2.77 ± 2.19
Molybdenum (mcg)
8.57 ± 8.17
22.0 ± 21.5
Phosphorus (mg)
487 ± 224
511 ± 285
Potassium (mg)
1364 ± 692
1678 ± 985
Selenium (mcg)
42.1 ± 23.3
27.2 ± 11.3
Sodium (mg)
2867 ± 948
1747 ± 694
Zinc (mg)
5.72 ± 4.28
5.42 ± 4.49
Choline (mg)
104 ± 58.3
92.6 ± 47.5
The data are expressed as mean ± SD (standard deviation)
t
df
p-value
2.50
2.26
-0.72
-0.79
29.00
14.61
29.00
29.00
.018
.039
.480
.433
-1.14
29.00
.263
-0.75
0.75
1.01
-0.61
-0.52
1.95
3.26
0.82
0.28
2.06
1.30
2.39
1.96
1.99
0.26
1.04
-2.05
-3.53
-0.19
-0.58
29.00
11.47
11.05
29.00
29.00
13.47
12.31
29.00
29.00
29.00
11.98
29.00
13.55
11.79
29.00
29.00
29.00
29.00
29.00
29.00
.458
.470
.334
.549
.610
.072
.007
.420
.779
.049
.220
.023
.071
.070
.800
.306
.049
.001
.851
.564
Table 5 showed significantly higher intakes of selenium and sodium in omnivore
group. Intake of vitamin A, beta-carotene, vitamin K, and magnesium, were significantly
lower in omnivore group. Folate, manganese, and molybdenum intakes were not
30
significant between vegetarians and omnivores. Their p-values were approaching 0.05
(0.072, 0.71, 0.70 respectively) which indicated with larger samples, the differences
might became significant.
Omnivore group met the RDA/AI requirements except for dietary fiber, n-3
PUFA, n-6 PUFA, vitamin A, vitamin D, folate DFE, vitamin K, calcium, chromium,
copper, iron, magnesium, molybdenum, phosphorus, potassium, selenium, zinc, and
choline. Omnivore group had significantly lower intake than EAR requirements in folate
DFE, calcium, iron, magnesium, and molybdenum.
Vegetarian had significantly lower intake compared to RDA/AI in n-3 PUFA, n-6
PUFA, vitamin B3, vitamin D, calcium, chromium, magnesium, molybdenum,
phosphorus, potassium, selenium, and choline. When compared to EAR requirements,
vegetarian group had significantly lower intake in calcium, iron, and selenium.
Some of the participants in both groups took nutritional supplements. Two
participants adhering to vegetarian diet (17%) were taking supplements: one participant
was taking vitamin B12 (500 mcg), vitamin C (500 mg), and folate (800mcg); another
participant was taking multivitamin supplement. Five participants (all females) adhering
to omnivorous diet (24%) were taking supplements: one participant was taking vitamin E
(400 IU); one participant was taking multivitamin supplement; one participant was taking
glucosamine HCl (1500 mg) with MSM (1500 mg); one participant was taking calcium
(500 mg) and vitamin C (1000 mg); and one participant was taking omega-3 (1000 mg),
vitamin B complex, vitamin C (500 mg), and glucosamine and chondroitin.
31
Table 6
Recommended Dietary Allowance (RDA), Adequate Intake (AI), and Estimated Average
Requirement (EAR) comparison to omnivore and vegetarian group
Diet
RDA
/AI*1
EAR2
Omnivore
(n=19)
Mean ± SD
220 ± 60.3
19.0 ± 6.74
0.46 ± 0.30
2.7 ± 1.37
417 ± 237
p1
p2
Vegetarian
(n=12)
Mean ± SD
221 ± 85.3
29.3 ± 14.9
0.42 ± 0.28
3.19 ± 1.74
653 ± 283
p1
p2
Carbohydrate (g) 130
100
.000 .000
.000 .000
Dietary Fiber (g)
25
-.001 -.335 -n-3 PUFA (g)
1.1
-.000 -.000 -n-6 PUFA (g)
12
-.000 -.000 -Vitamin A
500
.000 .145
.575 .088
700
(RAE)
Vitamin B1 (mg)
0.9
2.92 ± 9.21 .401 .352
1.00 ± 0.89
.701 .709
1.1
Vitamin B2 (mg)
0.9
3.13 ± 9.71 .375 .330
0.88 ± 0.55
.203 .920
1.1
Vitamin B3-NE
11
17.7 ± 18.5 .402 .135
11.2 ± 7.99
.001 .945
14
(mg)
Vitamin B6 (mg)
1.1
3.29 ± 9.78 .386 .342
1.15 ± 0.83
.544 .000
1.3
Vitamin B12
2
5.49 ± 10.6 .222 .170
18.1 ± 57.9
.367 .355
2.4
(mcg)
Biotin (mcg)
30
-16.1 ± 35.0 .101 -183 ± 574
.373 -Vitamin C (mg)
60
169
±
232
.094
.055
126
±
98.8
.101 .041
75
Vitamin D (mcg)
10
2.18 ± 1.50 .000 .000
1.77 ± 2.95
.000 .000
15
Folate, DFE
320
149 ± 106 .000 .000
299 ± 253
.195 .781
400
(mcg)
Vitamin K (mcg)
90
-43.7 ± 48.5 .001 -198 ± 159
.038 -Calcium (mg)
800
645 ± 231 .000 .009
720 ± 281
.005 .000
1000
Chromium (mcg)
25
-3.58 ± 6.85 .000
-4.31 ± 7.18
.000 -Copper (mg)
0.7
0.54 ± 0.35 .000 .064
0.86 ± 0.51
.775 .304
0.9
Iron (mg)
8.1
11.2 ± 3.33 .000 .010
16.0 ± 12.6
.584 .053
18
Magnesium (mg) 310
255
125 ± 64.8 .000 .000
210 ± 131
.022 .255
Manganese (mg)
1.8
-1.46 ± 0.93 .129 -2.77 ± 2.19
.153 -Molybdenum
34
8.57 ± 8.17 .000 .000
22.0 ± 21.5
.005 .095
45
(mcg)
Phosphorus (mg) 700
580
487 ± 224 .001 .089
511 ± 285
.000 .419
Potassium (mg)
4700
-1364 ± 692 .000 -1678 ± 985
.042 -Selenium (mcg)
45
42.1 ± 23.3 .026 .591
27.2 ± 11.3
.000 .000
55
Sodium (mg)
1500
-2867 ± 948 .033 -1747 ± 694
.243 -Zinc (mg)
6.8
5.72
±
4.28
.000
.288
5.42
±
4.49
.072 .310
8
Choline (mg)
425
-104 ± 58.3 .000 -92.6 ± 47.5
.000 -The data are expressed as mean ± SD (standard deviation)
* Recommended Dietary Allowances (RDAs) is in bold type and Adequate Intakes (AI)
is in ordinary type.
1,2
The comparison of nutrients mean value to RDA/AI and EAR respectively
32
CHAPTER 5
DISCUSSION
Macronutrients
Energy
There was no significant difference in energy intakes between vegetarian group
and omnivore group in total calories, total fat, and carbohydrate intakes. Total protein
intakes showed significant difference in protein intake Even though vegetarians are
often assumed to have lower BMI (Rizzo, Jaceldo-Siegl, Sabate, & Fraser, 2013), this
study showed similar BMI between the diet groups, which might due to similar energy
intake. Mean macronutrient compositions were significantly different between the diet
group in saturated fat, cholesterol, and protein, which were lower in vegetarian group.
The total carbohydrate, protein, and fat distribution in both group fell into the range of
AMDR (Food and Nutrition Board & Institute of Medicine, 2005).
Protein
The mean intake of protein in vegetarian group was significantly lower than
omnivore group. This finding was as expected, it was consistent with results from other
studies comparing vegetarian and omnivore diets (Clarys, Deriemaeker, Huybrechts,
Hebbelinck, & Mullie, 2013; Davey, Spencer, Appleby, Allen, Knox, & Key, 2003;
Knurick, Johnston, Wherry, & Aguayo, 2015). Although the intakes of vegan women
were marginal, but the intakes of vegans and LOVs usually meet the requirement of
protein recommendation (Alexander, Ball, & Mann, 1994; Larsson & Johansson, 2002;
McStay & Cunningham, 2009; Smith, Burke, & Wing, 2000; Tonstad, Butler, Yan, &
Fraser, 2009). Studies indicated that complementary proteins in plant foods in appropriate
33
amounts are able to supply adequate protein for maintenance of health and function. The
complementary proteins do not need to be consumed at the same time, eating it over the
course of a day can provide all essential amino acids (Young & Pellett, 1994).
Although the vegetarian protein intake in this study was higher than RDA
(46g/day), the lower intake in vegetarian compared to omnivore might be a concern.
Studies demonstrated that dietary protein is important for bone accrual and reduced
fracture risk in older adults. A cohort study in 1865 female participants with a 25 year
follow-up reported a significantly higher incidence of wrist fracture in vegetarians as
compared to omnivores and that higher intake of plant proteins reduced this risk by 68%
(Thorpe, Knutsen, Beeson, Rajaram, & Fraser, 2008). Another study also reported a
significant positive association of animal protein intake on bone accrual after controlling
for calcium intake (Nieves et al., 2010).
Fat
The results showed that vegetarians had lower intakes in saturated fat and
cholesterol compared to omnivores. It was in agreement with findings from other
studies. However, the vegetarians in those studies also consumed less fat and more
carbohydrate (Clarys, Deriemaeker, Huybrechts, Hebbelinck, & Mullie, 2013; Davey,
Spencer, Appleby, Allen, Knox, & Key, 2003). In the present study, there was no
significant difference in carbohydrate and total fat intake between vegetarians and
omnivores. Similar total fat intake in both diet groups indicating vegetarians made a
healthier diet choice in consuming less saturated fat, less cholesterol, more polyunsaturated fatty acid, and more mono-unsaturated fatty acid. Together with higher intake
of dietary fiber, vegetarians were at lower risk of death from ischemic heart disease than
34
omnivores (Key et al., 1999). The levels of saturated fatty acids are directly correlated
with CHD (Simon, Hodgkins, Browner, Neuhaus, Bernert, & Hulley, 1995).
n-3 PUFA
Adequate vegetarian group had a lower n-3 PUFA intakes compared to omnivore
group, although it is not statistically insignificant (p=0.436). Vegetarian group did not
meet the AI recommendation (1.1 g/day) with mean intake 38% of AI. Omnivore group
also did not meet the AI recommendation with 42% of AI. Only one participant was taking
omega-3 supplement (1000 mg), which did not influence the data analysis. Data analysis
still showed no statistical difference in n-3 PUFA intakes when all participants who were
taking supplements were excluded (Table 7). The new mean value for omnivore and
vegetarian did not meet the AI recommendation by 39% and 38% of AI respectively (Table
8).
Table 7
n-3 PUFA results between omnivores and vegetarians (include and exclude supplement)
Omnivore
Diet
n
Mean ± SD
n
19
0.46 ± 0.30
12
n-3 PUFA (g)
include suppl.
14
10
n-3 PUFA (g)
0.44 ± 0.27
exclude suppl.
The data are expressed as mean ± SD (standard deviation)
Vegetarian
Mean ± SD
pvalue
0.42 ± 0.28
.688
0.43± 0.30
.933
n-3 PUFAs are essential fatty acids since it cannot be synthesized endogenously
and must be provided in the diet (Food and Nutrition Board & Institute of Medicine,
2005). EPA and DHA are n-3 PUFAs important for cardiovascular health as well as eye
and brain development (Craig & Mangels, 2009). Although EPA and DHA can be
synthesized in the body from α-linolenic acid (ALA), which is largely available in plant-
35
based foods, the conversions to EPA is limited (less than 10%). The conversion to DHA
is substantially less than the conversion to EPA from α-linolenic acid (Rosell, LloydWright, Appleby, Sanders, Allen, & Key, 2005).
Table 8
n-3 PUFA comparison of Recommended Dietary Allowance (RDA), Adequate Intake (AI),
and Estimated Average Requirement (EAR) to omnivore and vegetarian groups (include
and exclude supplement)
Diet
n-3 PUFA (g)
include suppl.
RDA
/AI*1
1.1
Omnivore
p1
Vegetarian
p1
Mean ± SD
0.46 ± 0.30
.000
Mean ± SD
0.42 ± 0.28
.000
n-3 PUFA (g)
1.1
0.44 ± 0.27
.000
0.43± 0.30
.000
exclude suppl.
The data are expressed as mean ± SD (standard deviation)
* Recommended Dietary Allowances (RDAs) is in bold type and Adequate Intakes (AI)
is in ordinary type.
1,2
The comparison of nutrient’s mean value to RDA/AI
The similar results between vegetarians and omnivores might be due to low fish
consumption in omnivore participants. The EPIC-Norfolk cohort study reported that
vegans and meat-eaters, who did not consume any fish at all, had the lowest intake of
ALA. The total n-3 PUFA intakes were 57-80% lower in non-fish eaters than in fish
eaters. The status differences were significant, but considerably smaller than expected
(Welch, Shakya-Shrestha, Lentjes, Wareham, & Khaw, 2010). Low intake of n-3 PUFAs
in both group suggested the need to increase consumption of food rich of ALA or
supplements.
Fiber
In this study, the higher intake of dietary fiber among vegetarians than among
omnivores confirmed the results of another study of matched vegetarians and omnivores
participants (Clarys, Deriemaeker, Huybrechts, Hebbelinck, & Mullie, 2013). The present
36
study showed that vegetarians consumed more fiber-rich foods such as fruits, vegetables,
legumes, whole grains, and nuts (Dahl & Stewart, 2015). Studies have shown that higher
dietary fiber intakes reduce the risk of disease, including cardiovascular disease, type 2
diabetes, and colorectal cancer (Park et al., 2005; Threapleton et al., 2013; Ye, Chacko,
Chou, Kugizaki, & Liu, 2012). The RDI for fiber is the Adequate Intake (AI) as no
deficiency state has been demonstrated. The AI for fiber is based on the median fiber
intake level observed to achieve the lowest risk of coronary heart disease (CHD) (Food
and Nutrition Board & Institute of Medicine, 2005).
Micronutrients
Vitamin B12
The vitamin B12 intakes between vegetarians and omnivores were not
significantly different in this study. The mean intakes in both groups exceeded the EAR
requirement of 2 mcg/day; with omnivores met 275% of EAR and vegetarians met 755%
of EAR. As plant foods generally do not contain any vitamin B12, vegetarians, especially
vegans were expected to have lower intakes of this nutrient. The high intakes in both
groups might be due to intake of supplements which would influence the data analysis,
especially if the supplements were taken in high doses. One vegetarian participant was
taking 500 mcg of vitamin B12 and another participant was taking multivitamin
supplement. One omnivore participant was taking multivitamin supplement, and another
participant was taking vitamin B complex.
Table 9 showed the vitamin B12 mean intakes when all participants who were
taking supplements were excluded in analysis. Vegetarians showed significantly lower
mean vitamin B12 intake than omnivores. The mean intake of vitamin B12 in vegetarians
37
did not meet the EAR recommendation (46.5% of EAR), with omnivores met the EAR
recommendation (114.5% of EAR) (Table 10). The results were consistent with many
other studies, which showed low dietary vitamin B12 intakes in vegetarians and an
appropriate vitamin B12 intakes from diet only in omnivores (Davey, Spencer, Appleby,
Allen, Knox, & Key, 2003; Janelle & Barr, 1995; Schupbach, Wegmuller, Berguerand,
Bui, & Herter-Aeberli, 2015).
Table 9
Vitamin B12 results between omnivores and vegetarians (include and exclude
supplements)
Diet
n
19
Omnivore
Mean ± SD
5.49 ± 10.6
n
12
Vitamin B12 (mcg)
include suppl.
14
10
Vitamin B12 (mcg)
2.29 ± 1.42
exclude suppl.
The data are expressed as mean ± SD (standard deviation)
Vegetarian
Mean ± SD
18.1 ± 57.9
pvalue
.470
0.93 ± 0.79
.007
Table 10
Vitamin B12 comparison of Recommended Dietary Allowance (RDA), Adequate Intake
(AI), and Estimated Average Requirement (EAR) to omnivore and vegetarian groups
(include and exclude supplement)
Diet
RDA
/AI*1
EAR2
Omnivore
Mean ± SD
5.49 ± 10.6
p1
p2
Vegetarian
p1
p2
Mean ± SD
18.1 ± 57.9
Vitamin B12 (mcg) 2.4
2
.222 .170
.367 .355
Include suppl.
Vitamin B12 (mcg) 2.4
2
2.29 ± 1.42 .767 .464 0.93 ± 0.79 .000 .002
Exclude suppl.
The data are expressed as mean ± SD (standard deviation)
* Recommended Dietary Allowances (RDAs) is in bold type and Adequate Intakes (AI)
is in ordinary type.
1,2
The comparison of nutrient’s mean value to RDA/AI and EAR respectively
Vegetarians, with the exception of vegans, can obtain adequate vitamin B12 from
dairy foods, eggs, or other reliable vitamin B12 such as fortified foods; however, one
38
study showed that even LOV did not meet the vitamin B12 requirement from diet alone
(Janelle & Barr, 1995). Different study in young adults showed the results with no
supplement, that dietary vitamin B12 intakes in vegetarians were very low; however, the
prevalence of vitamin B12 deficiency was low throughout all participants, including
vegans and vegetarians. The author stated that 43% of vegans was taking supplements
sporadically, with no supplements were consumed throughout the duration of dietary
records (Larsson & Johansson, 2002). The other study in vegans showed one vegan
participant still had low vitamin B12 status despite taking vitamin B12 supplement,
which indicate the possibility of absorption failure (Larsson & Johansson, 2002). Despite
contrasting results in studies, it is advised for vegetarians to include vitamin B12 fortified
foods and/or dietary supplements in their diets to minimize the vitamin deficiency status
and meet the requirement intake of 2.4 mcg/day (RDA) for individuals (National
Academy of Sciences, Institute of Medicine, & Food and Nutrition Board, 1998).
Vitamin D
There is no difference in vitamin D intakes between omnivores and vegetarians.
Both mean intakes were significantly lower than EAR recommendation (5 mcg). The
mean intake of omnivores was 21.8% of EAR and the mean intake of vegetarians was
17.7% of EAR. These findings were in line with another study that showed lower vitamin
D intakes in vegetarian and vegan groups. Their overall vitamin D intake was also low in
all three diet groups (Schupbach, Wegmuller, Berguerand, Bui, & Herter-Aeberli, 2015).
Low intake of vitamin D may not indicate a potential risk for low vitamin D status. The
active metabolite of vitamin D, 1.25-dihydroxyvitamin D3, can be synthesized in the skin
through sunlight exposure, which varies between individuals; therefore vitamin D intake
39
is a poor indicator of vitamin D status (Appleby, Roddam, Allen, & Key, 2007). Only a
few foods contain vitamin D, which are mostly from animal source such as fish liver oils,
fatty fish, liver, and eggs. Other sources are fortified foods like cereals, milk, and soy
drinks (Larsson & Johansson, 2002; Lips, Graafmans, Ooms, Bezemer, & Bouter, 1996).
If sun exposure and fortified foods are insufficient to meet needs, vitamin D supplements
may be needed (Appleby, Roddam, Allen, & Key, 2007).
Calcium
Calcium is one of the factors known to be associated with bone health and
fracture risk (Appleby, Roddam, Allen, & Key, 2007). This study showed similar intake
in calcium between vegetarians and omnivores; however, both mean intakes were
significantly lower than EAR recommendation (800 mg/day). The mean intake of
vegetarian group was 90% of EAR and the mean intake of omnivore group was 81% of
EAR. Since most of the participants in vegetarian group were LOVs, milk was also
included in their diet. It explained the similar intake to omnivore group in this study. This
result was consistent with some studies that showed that LOVs who include milk in their
diet had similar intake to, or higher intake than those of omnivores (Davey, Spencer,
Appleby, Allen, Knox, & Key, 2003; Janelle & Barr, 1995; Schupbach, Wegmuller,
Berguerand, Bui, & Herter-Aeberli, 2015). A meta-analysis study showed that vegetarian
diets, particularly vegan diets, were associated with lower bone mineral density (BMD),
but the association was clinically insignificant (Ho-Pham, Nguyen, & Nguyen, 2009).
Other study in BMD also showed that plant-based diets were not detrimental to bone in
young adults; however, the author stated that the study cannot provide insights regarding
the impact of vegetarian diets on bone health in older adults. Nonetheless, adequate levels
40
of dietary calcium (≥1000 mg/day of RDA) are necessary to ensure bone health (Knurick,
Johnston, Wherry, & Aguayo, 2015).
Iron
There was no significant difference in iron intakes between vegetarian diet and
omnivore diet. When compared to EAR recommendation (8.1 mg/day) both groups
achieved the recommendation by 137% for omnivore group and 196% for vegetarian
group. This results were consistent with previous studies that showed similar iron intakes
in omnivore and vegetarian diets, with vegan participants showing the highest intake in
iron (Davey, Spencer, Appleby, Allen, Knox, & Key, 2003; Janelle & Barr, 1995;
Larsson & Johansson, 2002). Despite the similar intakes in both groups, vegetarian diet
was likely to have less iron absorption because of differences in the chemical form of
iron and the presence of iron inhibitors such as phytates and tannins (Hunt, 2003).
The lower availability of iron from plant-based food resulted in the
recommendation of iron intakes for vegetarians as 1.8 times as those of omnivores (Food
and Nutrition Board & Institute of Medicine, 2001). Iron deficiency will cause anemia
which can further impair work performance and cognitive process; however, low intakes
of iron over a long term period will lead to adaptation where the iron absorption will
increase and iron losses will decrease (Hunt & Roughead, 2000). A study also showed
that although vegans had the highest iron intakes, omnivores had a significantly higher
iron status compared to vegetarians and vegans (Schupbach, Wegmuller, Berguerand,
Bui, & Herter-Aeberli, 2015). Another study showed the incidence of iron deficiency
anemia is similar to that of omnivores. The vegetarian adults have normal serum ferritin
41
levels, which indicate that their iron status is within the normal range (Alexander, Ball, &
Mann, 1994).
The lower availability of iron from plant-based food resulted in the
recommendation of iron intakes for vegetarians as 1.8 times as those of omnivores (Food
and Nutrition Board & Institute of Medicine, 2001). Iron deficiency will cause anemia
which can further impair work performance and cognitive process; however, low intakes
of iron over a long term period will lead to adaptation where the iron absorption will
increase and iron losses will decrease (Hunt & Roughead, 2000).
Zinc
This study found similar zinc intake in both groups, in contrast with previous
studies resulting in higher zinc intake in omnivores compared to vegetarian (Davey,
Spencer, Appleby, Allen, Knox, & Key, 2003; Larsson & Johansson, 2002). Both diet
groups consumed less zinc than recommended by EAR (6.8 mg/day) (Food and Nutrition
Board & Institute of Medicine, 2001), 84% of EAR for omnivores and 80% of EAR for
vegetarians; however, it was not significant. Although the zinc intakes were similar
between vegetarians and omnivores, vegetarians were likely to have lower zinc status due
to the high amount of phytic acid, a zinc absorption inhibitor, in plant foods rich in zinc
such as legumes, whole grains, nuts, and seeds. Bioavailability of zinc is enhanced by
dietary protein, but plant sources of protein are also generally high in phytic acid (Hunt,
2003). The Dietary Reference Intakes for zinc suggested that, because of lower
absorption of zinc, those consuming vegetarian diets may require as much as 50% more
zinc than nonvegetarians (Food and Nutrition Board & Institute of Medicine, 2001). LOV
42
and vegan diets were categorized by World Health Organization publication with 30-35%
absorption in zinc bioavailability (World health Organization, 1996).
43
CHAPTER 6
CONCLUSION
There are many different types of diets. Most diets can be classified into
vegetarians and omnivorous (Craig & Mangels, 2009). Vegetarians are defined as
individuals who do not eat any meat (including fowl), poultry, fish, or products
containing these foods at all (Craig & Mangels, 2009). The food habits of vegetarians
may vary considerably. Based on their dietary intake, vegetarians may be classified as
either lacto ovo-vegetarians (LOVs) or vegans. LOVs are those who eat grains,
vegetables, fruits, legumes, seeds, nuts, dairy products, and eggs. Vegans (or total
vegetarians) are those who do not eat eggs, dairy, or other animal products. Omnivores
are people who do not have any dietary restrictions or people who include poultry,
poultry products, dairy, dairy products, fish, fish products, meat, and meat products in
their diet beside plant based foods (Craig & Mangels, 2009).
The numbers of vegetarians in the US is steadily increasing even though it
comprise only a small proportion of the population. Based on nationwide polls, the
number of US adult population who consistently followed a vegetarian diet increased
from 2.3% in 2006 to 4% in 2012 (McStay & Cunningham, 2009; Stahler, 2006; Stahler,
2012). However, the percentage of vegan decreased slightly from 1.4% to 0.8% (McStay
& Cunningham, 2009; Stahler, 2006). This means that approximately 7.5 million people
in the US are vegetarians. A recent survey showed that 21 % of college students are
vegans or vegetarians or flexitarians as determined by limiting meat consumption, eating
only certain types of meat, or eating meat only occasionally (Techtomic, 2011).
44
The increased number of people consuming vegetarian diets influence
foodservices, and they responded by offering vegetarian option at all meals. Sodexo
reported that 71% of their foodservice clients in the US are offering vegetarian option at
their sites (Sodexo, 2010). Additionally, the total US retail sales of vegetarian foods
increased significantly from $ 815 million in 2001 to $ 1.4 billion in 2008 (Mintel, 2007).
It is possible that one type of diet may be more adequate than other diets, if it
complies with the Dietary Reference Intakes (DRIs) (Food and Nutrition Board, Institute
of Medicine, & National Academies, 2011), Healthy Eating Index (Guenther et al., 2013),
or My Plate (United States Department of Agriculture, 2014) . Additionally, there might
be lower risks for certain chronic diseases when certain types of diets are followed.
Vegan diets combined with very low fat diets appeared to be useful for increasing the
intake of protective nutrients (antioxidant vitamins, carotenoids, and fiber) and
phytochemicals. This diet combination also minimize intake of pathogenic dietary factors
such as saturated fat and cholesterol, which are implicated in some chronic diseases
(Dewell, Weidner, Sumner, Chi, & Ornish, 2008).
It is important to look for low intakes of nutrients in certain diets, because of the
health risks that can accompany nutrient deficiencies or chronic low intake of important
nutrients in the diet, such as the risk of bone fracture due to calcium and vitamin D
deficiency (Appleby, Roddam, Allen, & Key, 2007), anemia due to iron and zinc
deficiency (Lozoff, Brittenham, Viteri, Wolf, & Urrutia, 1982), neurological symptoms
due to vitamin B12 deficiency and n-3 polyunsaturated fatty acids (PUFAs) (Janelle &
Barr, 1995; Trumbo, Schlicker, Yates, & Poos, 2002). The nutrient shortfalls for the
vegan diet are calcium, iron, zinc, vitamin B12, vitamin D, riboflavin, and n-3 PUFAs
45
(Alexander, Ball, & Mann, 1994; Craig, 2010; Davey, Spencer, Appleby, Allen, Knox, &
Key, 2003; Larsson & Johansson, 2002). Vegetarians have nutrient risks similar to vegan
such as iron, zinc, and vitamin B12; however they would have adequate intake of
calcium, vitamin D, and n-3 PUFAs since they still consume eggs and dairy products
(Craig, 2010). Since milk is the major source of calcium, LOVs who include milk in their
diet showed similar intake to, or higher intake, than those of omnivores (Weaver &
Plawecki, 1994Weaver & Plawecki, 1994).
There were considerable amount of studies done on vegans or vegetarians;
however, study that targets college students has not been done. The purpose of this study
was to assess the dietary intake of vegetarians and omnivores diet in college students by
comparing the energy and nutrient intake of each diet group to each other and assessing
whether each diet groups meet the Dietary Reference Intakes of America. The first
objective of this study was to determine if the energy intake of vegetarians is higher or
lower than the energy intake of omnivores. The second objective was to determine if
there are significant differences of nutrient intakes between vegetarians and omnivores.
The third objective was to determine whether each diet group meets the nutrient
recommendation based on Dietary Reference Intakes (DRIs), the Estimated Average
Requirements (EARs) and Adequate Intake (AIs).
To meet the first and second objectives, use of screening questionnaire and five
day-food and activity records were administered to 33 participants (n= 12 vegetarians
and n = 21 omnivores) on a volunteer basis. The answers to the screening questions were
reviewed and compared with the actual food records to determine whether the
participants fit into vegetarian or omnivorous diets. Lacto-ovo vegetarian (LOV)
46
individuals are defined as those who eat only plants, eggs, dairy, egg products, and dairy
products. Vegan individuals are defined as those who eat only plants and plant products.
Omnivorous individuals are defined as those who eat plants, eggs, dairy, meat, and meat
products. The participants then submitted five day food and physical activity records.
Results on the 33 participants were further analyzed using SPSS for WINDOWS (version
22; SPSS Inc., Chicago, IL, USA).
Within comparison of energy intake in both groups, it was determined that the pvalue of energy intakes between vegetarians and omnivores was more than 0.05 (p =
0.198). It suggested that there were no significant difference in energy intakes between
the two diet groups.
To determine the second null hypothesis (Ho) which stated “There will be no
significant difference of nutrient intakes between vegetarians and omnivores,” analysis of
mean intake values of the macronutrients and micronutrients were done using the
independent-sample T-test. The data of two male omnivorous participants were removed
since there was no male participant in the vegetarian group. Vegetarians had lower
intakes of protein, saturated fat, cholesterol, selenium, and sodium compared to the
omnivores participants. Fiber, vitamin A, beta-carotene, vitamin K, copper, and
magnesium intakes were significantly higher for the vegetarians compared to the
omnivore participants.
The determine whether nutrient intakes in each diet group meet the RDIs, the
mean nutrient intakes of each diet groups (19 females omnivores and 14 females
vegetarian) were compared to the recommendation values (RDA, AI, or EAR) using
Student’s T-test. The mean nutrient intakes that were lower than recommendation, with
47
p-values below 0.05 indicate the nutrient intakes did not meet the DRI recommendations.
Omnivore group had significantly lower intakes than AI/EAR in dietary fiber, n-3 PUFA,
n-6 PUFA, vitamin D, folate DFE, vitamin K, calcium, chromium, iron, magnesium,
molybdenum, and choline. The vegetarian group had significantly lower intakes than
AI/EAR in n-3 PUFA, n-6 PUFA, vitamin D, calcium, chromium, selenium, and choline.
According to this results, the dietary intake of vegetarian in college students were
able to meet the macronutrient recommendations of DRIs. However, it is advised for
vegetarians to include dietary supplement of n-3 PUFA, calcium, vitamin D, and vitamin
B12 in their diets. Based on this study, the omnivore college students might also need to
include more nutrient dense food in their diet and some dietary supplement like n-3
PUFA, calcium, and vitamin D.
Further research with bigger sample and nutritional status analyses are needed to
confirm the effect of nutrient intake on nutritional status in college students.
48
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APPENDIX A
IRB APPROVAL FORMS
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61
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APPENDIX B
SAMPLE OF CONSENT FORM
63
APPENDIX C
SCREENING QUESTIONNAIRE
64
5. How often do you eat dairy foods (milk, cheese, yogurt)?
Never
Occasionally (Once or twice a month)
A few times per week
Daily
6. How often do you eat egg and its products?
Never
Occasionally (Once or twice a month)
A few times per week
Daily
7. How often do you exercise (planned and structured physical activities)?
Once a week
Twice a week
Three times a week
More than three times a week
Not at all
Others _____________________________________
8. What type of exercises do you do everyday? (Please list types of
activities/exercises & how long you exercised for/do those activities)
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________
9. Which of these supplements are you taking?
Vitamins
Minerals
Herbal and Plant
Omega-3 or cod liver oil
Glucosamine and chondroitin
I do not take any supplements
Others not listed _____________________________________
2 of 2
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APPENDIX D
SAMPLE OF FOOD AND ACTIVITY RECORD
Diet Record
Directions: Record what you eat and drink on the sheets provided or similar. As you
record each food, make careful note of the amount and how it was prepared (fried, baked
etc.). Estimate the amount to the nearest weight or fluid ounce, quarter cup, tablespoon,
or other common measure. It is suggested to bring a measuring cup with you to meals.
In guessing at the sizes of meat portions, it helps to know that a piece of meat the size of
the palm of your hand weighs about 3 or 4 ounces. It also helps to know that a slice of
cheese (such as sliced American cheese) or a 1 1/2-inch cube of cheese weighs about 1
ounce. If you are unable to estimate serving sizes, measure out servings the size of a cup,
tablespoon, and teaspoon onto a plate or into a bowl to see how they look. You may have
to break down mixed dishes to their ingredients.
The closer your approximations, the closer your actual intake will be reflected. Some
common errors include using weight ounces instead of fluid ounces. Record the liquids as
fluid ounces and the solids as weight oz. It is also very helpful to read the labels of the
foods you consume. If you eat name brand foods, please also include the name brand of
the food or the restaurant chain name if applicable.
Please record any nutrient supplements you take. Write your food records on the provided
charts (provided with this assignment). Be sure to list the amounts of foods eaten.
Some Common Portion Sizes:
http://www.win.niddk.nih.gov/publications/just_enough.htm
Serving Sizes
Everyday Objects
1 cup of cereal = a fist
1/2 cup of cooked rice, pasta, or potato = 1/2 baseball
66
1 baked potato = a fist
1 medium fruit = a baseball
1/2 cup of fresh fruit = 1/2 baseball
1 1/2 ounces of low-fat or fat-free cheese = 4 stacked
dice
1/2 cup of ice cream = 1/2 baseball
2 tablespoons of peanut butter = a ping-pong ball
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Activity Charts
Intensity:
Light: most sitting and standing activities. Activity examples are: Attending class,
studying, using a computer, watching TV, talking, doing homework, sleeping.
Moderate: breathing rate increases, but conversation is possible. Activity examples are:
walking moderately, cycling briskly, scrubbing floors, raking, car-washing, waiting
tables, washing dishes, social dancing, swimming, hitting a punching bag.
Vigorous or intense: too out of breath to easily carry on a conversation. Activity
examples are: hiking uphill, carrying heavy items, heavy construction work, running or
jogging, high impact exercises classes-aerobic or spinning, most competitive sports
Activity Chart-Day 1
Time
12:00 am
12:15 am
12:30 am
12:45 am
1:00 am
1:15 am
1:30 am
1:45 am
2:00 am
2:15 am
2:30 am
2:45 am
3:00 am
3:15 am
3:30 am
3:45 am
4:00 am
4:15 am
4:30 am
4:45 am
5:00 am
5:15 am
5:30 am
5:45 am
6:00 am
6:15 am
6:30 am
6:45 am
7:00 am
7:15 am
7:30 am
Date ____________
Activity
Intensity
68
Activity Chart Day -1
Time
7:45 am
8:00 am
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Activity
Intensity
69
Activity Chart Day -1
Time
Activity
Intensity
6:00 pm
6:15 pm
6:30 pm
6:45 pm
7:00 pm
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All activities should be completely filled in. Include sleeping hours.
70
Food Records Day- 1
TIME
FOOD/ BEVERAGE
Supplements Taken
Today
COOKING
METHOD
Brand
Amount
Taken
71
AMOUNT
What does it do?
APPENDIX E
SAMPLE OF RECRUITMENT FLYER
72
APPENDIX F
JOURNAL ARTICLE
Dietary differences between vegetarian and omnivore in college students
Stephanie Bunawan, Dr. Bonny Burn-Whitmore,
Dr. David Edens, and Aleida Gordon
California State Polytechnic University, Pomona
Abstract
Background. The numbers of the vegetarians in the United States (US) are
steadily increasing [1, 2], with 21% of college students are vegetarians [3].
Vegetarian diet has been associated with lower risks of certain chronic diseases;
however, vegetarians may have nutrient risks due to certain food limitation in their
diets [4, 5]. Objective. The purpose of this study was to assess the difference in
dietary intake of vegetarians and omnivores diet in college students and to
determine whether each diet group meets the Dietary Reference Intakes (DRI) of
America. Methods. Thirty three18-35 years old college students completed five-day
food and activity records, they were then grouped into vegetarian group (n=12) and
omnivore group (n=21) based on the self-reported food records. The dietary intakes
of both groups were then compared to the DRIs. Results. Vegetarians had lower
intakes of protein, saturated fat, cholesterol, selenium, and sodium; and higher
intakes in fiber, vitamin A, beta-carotene, vitamin K, copper, and magnesium when
compared to omnivores. Vegetarians did not reach the DRIs recommendation for n3 PUFA, n-6 PUFA, vitamin D, calcium, chromium, selenium, and choline. Omnivores
had lower intakes than RDIs in dietary fiber, n-3 PUFA, n-6 PUFA, vitamin D, folate,
vitamin K, calcium, chromium, iron, magnesium, molybdenum, and choline.
Conclusions. At the macronutrient level, vegetarian diet was in better accordance
with DRIs than omnivore diet. At the micronutrient level, both groups fall short in
certain nutrients, suggesting a need for greater attention to ensure adequate diet of
specific nutrients.
Introduction
There are many different types of diets. Most diets can be classified into
vegetarians and omnivorous [5]. Common reasons for choosing vegetarian diets are
based on health concerns, weight loss purposes, environmental concerns, animal
welfare factors, economic reasons, and religious reasons [5-8].
The numbers of vegetarians in the United States (US) comprise only a small
proportion of the population, but their number is steadily increasing [1, 9]. Based on
nationwide polls, the number of US adult population who consistently followed a
73
vegetarian diet increased from 2.3% in 2006 to 4% in 2012 [1, 2, 9]. A recent survey
showed that 21 % of college students are vegans or vegetarians or flexitarians [3].
The increased number of people consuming vegetarian diets influence foodservices,
and they responded by offering vegetarian option at all meals. Sodexo reported that
71% of their foodservice clients in the US are offering vegetarian option at their
sites [10]. Additionally, the total US retail sales of vegetarian foods increased
significantly from $ 815 million in 2001 to $ 1.4 billion in 2008 [11].
Vegetarian diets may have health benefits due to intake of low animal products,
which are higher in saturated fat and cholesterol than plant products (except palm
and coconut oil). Vegetarian diets contain higher amount of photochemical such as
flavonoids, products such as fiber, and other compounds that may have health
benefits [4].
It is possible that one type of diet may be more adequate than other diets, if it
complies with the Dietary Reference Intakes (DRIs) [12], Healthy Eating Index [13],
or My Plate [14] . Additionally, there might be lower risks for certain chronic
diseases when certain types of diets are followed. Vegan diets combined with very
low fat diets appeared to be useful for increasing the intake of protective nutrients
(antioxidant vitamins, carotenoids, and fiber) and phytochemicals. This diet
combination also minimize intake of pathogenic dietary factors such as saturated fat
and cholesterol, which are implicated in some chronic diseases [15].
It is important to look for low intakes of nutrients in certain diets, because of the
health risks that can accompany nutrient deficiencies or chronic low intake of
important nutrients in the diet [6, 16-18]. The nutrient shortfalls for the vegan diet
are calcium, iron, zinc, vitamin B12, vitamin D, riboflavin, and n-3 PUFAs [19-22].
Vegetarians have nutrient risks similar to vegan such as iron, zinc, and vitamin B12;
however they would have adequate intake of calcium, vitamin D, riboflavin and n-3
PUFAs since they still consume eggs and dairy products [19] Therefore, the overall
purpose of this study is to evaluate the dietary intake of vegetarians and omnivores
diet in college students. The diet comparison is being conducted to evaluate whether
differences in essential vitamins and minerals exist among those consuming a
vegetarian or an omnivorous diet. Each diet group will also be compared to DRIs to
determine whether each group is receiving adequate or less than or greater than
adequate amounts of both essential nutrients and non-essential foods (saturated
fat/ trans fatty acids).
Methods
Participants
The study was performed at California State Polytechnic (Cal Poly)
University Pomona and Loma Linda University (LLU). The Cal Poly Pomona
Institutional Review Board and LLU Institutional Review Board approved the study
protocol # 11-138. All participants were provided written informed consent.
74
Participants were recruited of February 2011 until December 2014 via emails,
presentation, and flyers on Cal Poly Pomona campus and LLU. Some recruitment
was also accomplished by the word of mouth, in which participants were asked to
speak with acquaintances about the study. The inclusion criteria for this study were
participants had to be healthy, between the ages of 18 and 35 years, not pregnant or
lactating. Thirty three healthy age 18-35 year old college students completed the
course of the study. Based on self-reported diet habits and the actual food records,
participants were grouped into two diet groups, vegetarian (n=12) and omnivore
(n=21).
Dietary Assessment
After the participants signed the consent form and filled out the screening
questionnaire, five randomized day food and activity records were given for them to
complete. In the screening questionnaire, participants answered the questions given
about their habitual diet (what diet are they considering themselves practicing, age,
gender, how often they eat meat and fish, how often do they eat dairy, and what type
of supplements they take). Their physical activity level was also asked, since it may
relate to the amount of food they consumed. The answers to the screening questions
were reviewed and were compared with the actual food records to determine
whether they fit into vegetarian and omnivorous diets. LOV individuals are defined
as those who eat only plants, eggs, dairy, egg products, and dairy products. Vegan
individuals are defined as those who eat only plants and plant products.
Omnivorous individuals are defined as those who eat plants, eggs, dairy, meat, and
meat products. The participants then submitted five day food and physical activity
records.
The five days for which the participants kept the food records were randomized by
the researcher using a random number generator for each diet group [23]. The five
day food and physical activity records were completed within 90 days. After filling
out the diet and exercise log, the participant emailed or gave the form back to the
researcher.
Data analysis
The nutritional composition of each food was determined using the Food
Processor Nutrition and Fitness software [24]. The amount of nutrients in each diet
group were calculated and averaged, and then compared to nutrient
recommendations by Dietary Reference Intakes (DRIs) [12]. The mean of the energy
and nutrient intakes were also used for comparison for three different diet groups
that were being studied.
Statistical methods
Statistical information was obtained using SPSS for WINDOWS (version 22;
SPSS Inc., Chicago, IL, USA). Data were reported as mean ± SD. A p value of ≤
0.05was considered statistically significant.
75
The first objective of this study was to compare the energy intake of each diet
group to the other diet group using independent-samples T-test. The second
objective of this study was to compare the nutrient intake of each diet group to each
other using independent-samples T-test. The nutrients that were evaluated were all
nutrients that are recommended by DRIs. The third objective of this study was to
compare the nutrient value to the DRI requirements (RDA, AI, and EAR) using
Student’s t-test.
Results
A total of 74 participants signed the consent forms and completed the
screening questionnaires. The five day food and activity records were returned by
33 participants. Based on self-reported diet habits, participants were grouped into
two diet groups, vegetarian (n = 12) and omnivore (n = 21). Participants in the
vegetarian group were all female. Participants in the omnivore group were 2 males
and 19 females. Age, body weight, height, and BMI did not differ significantly
between vegetarians and omnivores (p>0.05). Table 1 shows the characteristics of
the study population by diet group.
Table 1 Participant characteristics by diet group
Gender, M/F
Age (year)
Body weight (lb)
Height (inch)
BMI (lb/inch2)
Omnivore
Mean ± SD
2/19
23.3 ± 3.08
133 ± 23.4
58.6 ± 3.08
23.3 ± 3.85
Vegetarian
Mean ± SD
0/12
25.1 ± 5.27
132 ± 26.9
64.2 ± 2.63
22.5 ± 4.46
p-value
0.286
0.937
0.345
0.604
The data of two male omnivorous participants was removed since there was
no male participant in the vegetarian group. The mean nutrient intakes of each diet
groups (19 females omnivores and 14 females vegetarian) then was compared
again (Table 2 and Table 3).
Each nutrient value was compared to Dietary Reference Intakes (DRIs) of
females in 19-40 years old life stage (Table 4). Nutrients that were compared were
the macronutrients, along with nutrients of concern in the vegetarian diets: vitamin
B12, vitamin D, riboflavin, calcium, iron, and zinc (Alexander, Ball, & Mann, 1994;
Craig, 2010). The DRIs are reference values that are quantitative estimates of
nutrient intakes to be used for planning and assessing diets for healthy people [25].
The reference values include the Estimated Average Requirement (EAR),
Recommended Dietary Allowance (RDA), the Adequate Intake (AI), the Tolerable
Upper Intake Level (UL), the Estimated Energy Requirement (EER), and the
76
Acceptable Macronutrient Distribution Range (AMDR). RDA and AI were commonly
used in studies to measure the nutrient adequacy in individuals. EAR was used to
measure the nutrient adequacy in a diet group [25].
Table 2 Macronutrient intake (including supplement) between female vegetarians and
female omnivores
Diet
Calories (kcal)
Protein (g)
Carbohydrates (g)
Dietary Fiber (g)
Fat (g)
Saturated Fatty Acids (g)
Monounsaturated fat (g)
Polyunsaturated fat (g)
n- 3 PUFA (g)
n- 6 PUFA (g)
Trans Fatty Acid (g)
Cholesterol (mg)
Alcohol (g)
Omnivore
(n = 19)
Mean ± SD
1687 ± 403
74.1 ± 19.1
220 ± 60.3
19.0 ± 6.74
58.4 ± 15.1
17.7 ± 5.81
9.77 ± 5.50
4.68 ± 2.27
0.46 ± 0.30
2.71 ± 1.37
0.57 ± 0.51
233 ± 173
0.04 ± 0.11
Vegetarian
(n=12)
Mean ± SD
1525 ± 405
52.4 ± 18.1
221 ± 85.3
29.3 ± 14.9
52.7 ± 16.3
13.6 ± 4.57
11.8 ± 6.79
6.99 ± 4.48
0.42 ± 0.28
3.19 ± 1.74
0.34 ± 0.45
92.3 ± 92.6
0.31 ± 1.08
t
df
p-value
-1.08
-3.14
0.04
2.27
-0.99
-2.07
.931
1.66
-0.41
-0.86
-1.28
-2.59
0.87
29.0
29.0
29.0
13.8
29.0
29.0
29.0
14.6
29.0
29.0
29.0
29.0
11.2
.287
.004
.970
.040
.330
.047
.359
.119
.688
.398
.210
.015
.404
The data are expressed as mean ± SD (standard deviation)
Mean calories intake did not differ between vegetarian and omnivore
participants (p > 0.05) (Table 2). Macronutrient intake analysis showed no
significant differences between carbohydrate intake, total fat intake, n-3 PUFA, n-6
PUFA, and trans fatty acid of vegetarian and the omnivore participants. Omnivore
participants had significantly higher protein, saturated fatty acids and cholesterol
intakes; also significantly lower dietary fiber intake. Table 5 showed significant
higher intakes of selenium and sodium in omnivore group. Intake of vitamin A, betacarotene, vitamin K, and magnesium were significantly lower in omnivore group.
77
Table 3 Dietary intake of vitamins and minerals (including supplement) between
female vegetarians and female omnivores
Diet
Vitamin A-RAE (RAE)
Beta-Carotene (mcg)
Vitamin B1 (mg)
Vitamin B2 (mg)
Vitamin B3-Niacin
Equivalent (mg)
Vitamin B6 (mg)
Vitamin B12 (mcg)
Biotin (mcg)
Vitamin C (mg)
Vitamin D-mcg (mcg)
Folate, DFE (mcg)
Vitamin K (mcg)
Calcium (mg)
Chromium (mcg)
Copper (mg)
Iron (mg)
Magnesium (mg)
Manganese (mg)
Molybdenum (mcg)
Phosphorus (mg)
Potassium (mg)
Selenium (mcg)
Sodium (mg)
Zinc (mg)
Choline (mg)
Omnivore (n
= 19)
Mean ± SD
417 ± 237
2555 ± 1998
2.92 ± 9.21
3.13 ± 9.71
17.7 ± 18.5
3.29 ± 9.78
5.49 ± 10.6
16.1 ± 35.0
169 ± 232
2.18 ± 1.50
149 ± 106
43.7 ± 48.5
645 ± 231
3.58 ± 6.85
0.54 ± 0.35
11.2 ± 3.33
125 ± 64.8
1.46 ± 0.93
8.57 ± 8.17
487 ± 224
1364 ± 692
42.1 ± 23.3
2867 ± 948
5.72 ± 4.28
104 ± 58.3
Vegetarian
(n=12)
Mean ± SD
653 ± 283
5334 ± 3947
1.00 ± 0.89
0.88 ± 0.55
11.2 ± 7.99
1.15 ± 0.83
18.1 ± 57.9
183 ± 574
126 ± 98.8
1.77 ± 2.95
299 ± 253
198 ± 159
720 ± 281
4.31 ± 7.18
0.86 ± 0.51
16.0 ± 12.6
210 ± 131
2.77 ± 2.19
22.0 ± 21.5
511 ± 285
1678 ± 985
27.2 ± 11.3
1747 ± 694
5.42 ± 4.49
92.6 ± 47.5
t
df
p-value
2.50
2.26
-0.72
-0.79
29.00
14.61
29.00
29.00
.018
.039
.480
.433
-0.75
0.75
1.01
-0.61
-0.52
1.95
3.26
0.82
0.28
2.06
1.30
2.39
1.96
1.99
0.26
1.04
-2.05
-3.53
-0.19
-0.58
29.00
11.47
11.05
29.00
29.00
13.47
12.31
29.00
29.00
29.00
11.98
29.00
13.55
11.79
29.00
29.00
29.00
29.00
29.00
29.00
.458
.470
.334
.549
.610
.072
.007
.420
.779
.049
.220
.023
.071
.070
.800
.306
.049
.001
.851
.564
-1.14
The data are expressed as mean ± SD (standard deviation)
29.00
.263
Omnivore group met the AI requirements except for dietary fiber, n-3 PUFA,
n-6 PUFA, vitamin K, chromium, and choline. Omnivore group had significantly
lower intake than EAR requirements in folate DFE, calcium, iron, magnesium, and
molybdenum. Vegetarian had significantly lower intake compared to AI in n-3 PUFA,
n-6 PUFA, chromium, and choline. When compared to EAR requirements, vegetarian
group had significantly lower intake in calcium, iron, and selenium.
78
Table 4 Recommended Dietary Allowance (RDA), Adequate Intake (AI), and Estimated
Average Requirement (EAR) comparison to omnivore and vegetarian group
RDA
/AI*1
EAR2
Carbohydrate (g) 130
Dietary Fiber (g)
25
n-3 PUFA (g)
1.1
n-6 PUFA (g)
12
Vitamin A (RAE)
700
Vitamin B1 (mg)
1.1
Vitamin B2 (mg)
1.1
Vitamin B3-NE
14
(mg)
Vitamin B6 (mg)
1.3
Vitamin B12
2.4
(mcg)
Biotin (mcg)
30
Vitamin C (mg)
75
Vitamin D (mcg)
15
Folate, DFE (mcg) 400
Vitamin K (mcg)
90
Calcium (mg)
1000
Chromium (mcg)
25
Copper (mg)
0.9
Iron (mg)
18
Magnesium (mg) 310
Manganese (mg)
1.8
Molybdenum
45
(mcg)
Phosphorus (mg) 700
Potassium (mg)
4700
Selenium (mcg)
55
Sodium (mg)
1500
Zinc (mg)
8
Choline (mg)
425
Diet
Omnivore
(n=19)
p1
p2
Vegetarian
(n=12)
p1
p2
100
---500
0.9
0.9
11
Mean ± SD
220 ± 60.3
19.0 ± 6.74
0.46 ± 0.30
2.71 ± 1.37
417 ± 237
2.92 ± 9.21
3.13 ± 9.71
17.7 ± 18.5
.000
.001
.000
.000
.000
.401
.375
.402
.000
---.145
.352
.330
.135
Mean ± SD
221 ± 85.3
29.3 ± 14.9
0.42 ± 0.28
3.19 ± 1.74
653 ± 283
1.00 ± 0.89
0.88 ± 0.55
11.2 ± 7.99
.000
.335
.000
.000
.575
.701
.203
.001
.000
---.088
.709
.920
.945
-60
10
320
-800
-0.7
8.1
255
-34
16.1 ± 35.0
169 ± 232
2.18 ± 1.50
149 ± 106
43.7 ± 48.5
645 ± 231
3.58 ± 6.85
0.54 ± 0.35
11.2 ± 3.33
125 ± 64.8
1.46 ± 0.93
8.57 ± 8.17
.101
.094
.000
.000
.001
.000
.000
.000
.000
.000
.129
.000
-.055
.000
.000
-.009
-.064
.010
.000
-.000
183 ± 574
126 ± 98.8
1.77 ± 2.95
299 ± 253
198 ± 159
720 ± 281
4.31 ± 7.18
0.86 ± 0.51
16.0 ± 12.6
210 ± 131
2.77 ± 2.19
22.0 ± 21.5
.373
.101
.000
.195
.038
.005
.000
.775
.584
.022
.153
.005
-.041
.000
.781
-.000
-.304
.053
.255
-.095
1.1
2
580
-45
-6.8
--
3.29 ± 9.78
5.49 ± 10.6
487 ± 224
1364 ± 692
42.1 ± 23.3
2867 ± 948
5.72 ± 4.28
104 ± 58.3
.386
.222
.001
.000
.026
.033
.000
.000
.342
.170
.089
-.591
-.288
--
1.15 ± 0.83
18.1 ± 57.9
511 ± 285
1678 ± 985
27.2 ± 11.3
1747 ± 694
5.42 ± 4.49
92.6 ± 47.5
.544
.367
.000
.042
.000
.243
.072
.000
.000
.355
.419
-.000
-.310
--
The data are expressed as mean ± SD (standard deviation)
* Recommended Dietary Allowances (RDAs) is in bold type and Adequate Intakes
(AI) is in ordinary type.
1,2 The comparison of nutrient’s mean value to RDA/AI and EAR respectively
Discussion
Macronutrients
Energy. There was no significant difference in energy intakes between
vegetarian group and omnivore group. Even though vegetarians are often assumed
79
to have lower BMI [26], this study showed similar BMI between the diet groups.
Mean macronutrient compositions were significantly different between the diet
group in saturated fat, cholesterol, and protein, which were lower in vegetarian
group. The total carbohydrate, protein, and fat distribution in both group fell into
the range of AMDR [27].
Protein. The mean intake of protein in vegetarian group was significantly
lower than omnivore group. This finding was as expected. It was consistent with
results from other studies comparing vegetarian and omnivore diets [21, 28, 29].
The studies showed that although the intakes of vegan women were marginal, but
the intakes of vegans and LOVs usually meet the requirement of protein
recommendation [7, 9, 20, 22, 30]. Studies indicated that complementary proteins in
plant foods in appropriate amounts are able to supply adequate protein for
maintenance of health and function [31].
Although the vegetarian protein intake in this study was higher than RDA
(46g/day), the lower intake in vegetarian compared to omnivore might be a
concern. Studies demonstrated that dietary protein is important for bone accrual
and reduced fracture risk in older adults. A cohort study in 1865 female participants
with a 25 year follow-up reported a significantly higher incidence of wrist fracture
in vegetarians as compared to omnivores and that higher intake of plant proteins
reduced this risk by 68% [32]. Another study also reported a significant positive
association of animal protein intake on bone accrual after controlling for calcium
intake [33].
Fat. The results showed that vegetarians had lower intakes in saturated fat
and cholesterol compared to omnivores. It was in agreement with findings from
other studies. However, the vegetarians in those studies also consumed less fat and
more carbohydrate [21, 28]. In the present study, there was no significant difference
in carbohydrate and total fat intake between vegetarians and omnivores. Similar
total fat intake in both diet groups indicating vegetarians made a healthier diet
choice in consuming less saturated fat, less cholesterol, more poly-unsaturated fatty
acid, and more mono-unsaturated fatty acid. Another study showed that together
with higher intake of dietary fiber, vegetarians were at lower risk of death from
ischemic heart disease than omnivores [34]. The levels of saturated fatty acids are
directly correlated with CHD [35].
n-3 PUFA. Adequate vegetarian group had a lower n-3 PUFA intakes
compared to omnivore group, although it is not statistically insignificant (p=0.436).
Vegetarian group did not meet the AI recommendation (1.1 g/day) with mean intake
38% of AI. Omnivore group also did not meet the AI recommendation with 42% of AI.
Only one participant was taking omega-3 supplement (1000 mg), which did not
influence the data analysis. Data analysis still showed no statistical difference in n-3
PUFA intakes when all participants who were taking supplements were excluded (p=
80
0.933). The new mean value for omnivore and vegetarian did not meet the AI
recommendation by 39% and 38% of AI respectively.
n-3 PUFAs are essential fatty acids since it cannot be synthesized
endogenously and must be provided in the diet [27]. EPA and DHA are n-3 PUFAs
important for cardiovascular health as well as eye and brain development [5].
Although EPA and DHA can be synthesized in the body from α-linolenic acid (ALA),
which is largely available in plant-based foods, the conversions to EPA is limited
(less than 10%). The conversion to DHA is substantially less than the conversion to
EPA from α-linolenic acid [36].
The similar results between vegetarians and omnivores might be due to low
fish consumption in omnivore participants. The EPIC-Norfolk cohort study reported
that vegans and meat-eaters, who did not consume any fish at all, had the lowest
intake of ALA. The total n-3 PUFA intakes were 57-80% lower in non-fish eaters
than in fish eaters. The status differences were significant, but considerably smaller
than expected [37]. Low intake of n-3 PUFAs in both group suggested the need to
increase consumption of food rich of ALA or supplements.
Fiber. In this study, the higher intake of dietary fiber among vegetarians than
among omnivores confirmed the results of another study of matched vegetarians
and omnivores participants [28]. The present study showed that vegetarians
consumed more fiber-rich foods such as fruits, vegetables, legumes, whole grains,
and nuts [38]. Studies have shown that higher dietary fiber intakes reduce the risk
of disease, including cardiovascular disease, type 2 diabetes, and colorectal cancer
[39-41].
Micronutrients
Vitamin B12. The vitamin B12 intakes between vegetarians and omnivores were
not significantly different in this study. The mean intakes in both groups exceeded the
EAR requirement of 2 mcg/day; with omnivores met 275% of EAR and vegetarians met
755% of EAR. As plant foods generally do not contain any vitamin B12, vegetarians,
especially vegans were expected to have lower intakes of this nutrient. The high intakes
in both groups might be due to intake of supplements which would influence the data
analysis, especially if the supplements were taken in high doses. One vegetarian
participant was taking 500 mcg of vitamin B12 and another participant was taking
multivitamin supplement. One omnivore participant was taking multivitamin supplement,
and another participant was taking vitamin B complex.
Vegetarians showed significantly lower mean vitamin B12 intake than
omnivores when the supplements were excluded. The mean intake of vitamin B12 in
vegetarians did not meet the EAR recommendation (46.5% of EAR) (p=0.02), with
omnivores met the EAR recommendation (114.5% of EAR) (p=0.767). The results
were consistent with many other studies, which showed low dietary vitamin B12
81
intakes in vegetarians and an appropriate vitamin B12 intake from diet only in
omnivores [6, 21, 42].
Vegetarians, with the exception of vegans, can obtain adequate vitamin B12
from dairy foods, eggs, or other reliable vitamin B12 such as fortified foods;
however, one study showed that even LOV did not meet the vitamin B12
requirement from diet alone [6]. Different study in young adults showed the results
with no supplement, that dietary vitamin B12 intakes in vegetarians were very low;
however, the prevalence of vitamin B12 deficiency was low throughout all
participants, including vegans and vegetarians. The author stated that 43% of
vegans was taking supplements sporadically, with no supplements were consumed
throughout the duration of dietary records [22]. The other study in vegans showed
one vegan participant still had low vitamin B12 status despite taking vitamin B12
supplement, which indicate the possibility of absorption failure [22]. Despite
contrasting results in studies, it is advised for vegetarians to include vitamin B12
fortified foods and/or dietary supplements in their diets to minimize the vitamin
deficiency status and meet the requirement intake of 2.4 mcg/day (RDA) for
individuals [43].
Vitamin D. There is no difference in vitamin D intakes between omnivores
and vegetarians. Both mean intakes were significantly lower than EAR
recommendation (5 mcg). The mean intake of omnivores was 21.8% of EAR and the
mean intake of vegetarians was 17.7% of EAR. These findings were in line with
another study that showed lower vitamin D intakes in vegetarian and vegan groups.
Their overall vitamin D intake was also low in all three diet groups [42]. Low intake
of vitamin D may indicate a potential risk for low vitamin D status. The active
metabolite of vitamin D, 1.25-dihydroxyvitamin D3, can be synthesized in the skin
through sunlight exposure, which varies between individuals; therefore vitamin D
intake is a poor indicator of vitamin D status [16]. Only a few foods contain vitamin
D, which are mostly from animal source such as fish liver oils, fatty fish, liver, and
eggs. Other sources are fortified foods like cereals, milk, and soy drinks [22, 44]. If
sun exposure and fortified foods are insufficient to meet needs, vitamin D
supplements may be needed [16].
Calcium. Calcium is one of the factors known to be associated with bone
health and fracture risk [16]. This study showed similar intake in calcium between
vegetarians and omnivores; however, both mean intakes were significantly lower
than EAR recommendation (800 mg/day). The mean intake of vegetarian group was
90% of EAR and the mean intake of omnivore group was 81% of EAR. Since most of
the participants in vegetarian group were LOVs, milk was also included in their diet.
It explained the similar intake to omnivore group in this study. This result was
consistent with some studies that showed that LOVs who include milk in their diet
had similar intake to, or higher intake than those of omnivores [6, 21, 42]. A meta82
analysis study showed that vegetarian diets, particularly vegan diets, were
associated with lower bone mineral density (BMD), but the association was
clinically insignificant [45]. Other study in BMD also showed that plant-based diets
were not detrimental to bone in young adults; however, the author stated that the
study cannot provide insights regarding the impact of vegetarian diets on bone
health in older adults. Nonetheless, adequate levels of dietary calcium (≥1000
mg/day of RDA) are necessary to ensure bone health [29].
Iron. There was no significant difference in iron intakes between vegetarian
diet and omnivore diet. When compared to EAR recommendation (8.1 mg/day) both
groups achieved the recommendation by 137% for omnivore group and 196% for
vegetarian group. This results were consistent with previous studies that showed
similar iron intakes in omnivore and vegetarian diets, with vegan participants
showing the highest intake in iron [6, 21, 22]. Despite the similar intakes in both
groups, vegetarian diet was likely to have less iron absorption because of
differences in the chemical form of iron and the presence of iron inhibitors such as
phytates and tannins [46].
The lower availability of iron from plant-based food resulted in the
recommendation of iron intakes for vegetarians as 1.8 times as those of omnivores
[47]. Iron deficiency will cause anemia which can further impair work performance
and cognitive process; however, low intakes of iron over a long term period will
lead to adaptation where the iron absorption will increase and iron losses will
decrease [48]. A study also showed that although vegans had the highest iron
intakes, omnivores had a significantly higher iron status compared to vegetarians
and vegans [42]. Another study showed the incidence of iron deficiency anemia is
similar to that of omnivores. The vegetarian adults have normal serum ferritin
levels, which indicate that their iron status is within the normal range [20].
The lower availability of iron from plant-based food resulted in the
recommendation of iron intakes for vegetarians as 1.8 times as those of omnivores
[47]. Iron deficiency will cause anemia which can further impair work performance
and cognitive process; however, low intakes of iron over a long term period will
lead to adaptation where the iron absorption will increase and iron losses will
decrease [48].
Zinc. This study found similar zinc intake in both groups, in contrast with
previous studies resulting in higher zinc intake in omnivores compared to
vegetarian [21, 22]. Both diet groups consumed less zinc than recommended by EAR
(6.8 mg/day) [47], 84% of EAR for omnivores and 80% of EAR for vegetarians.
Although the zinc intakes were similar between vegetarians and omnivores,
vegetarians were likely to have lower zinc status due to the high amount of phytic
acid, a zinc absorption inhibitor, in plant foods rich in zinc such as legumes, whole
grains, nuts, and seeds. Bioavailability of zinc is enhanced by dietary protein, but
83
plant sources of protein are also generally high in phytic acid [46]. The Dietary
Reference Intakes for zinc suggested that, because of lower absorption of zinc, those
consuming vegetarian diets may require as much as 50% more zinc than
nonvegetarians [47]. LOV and vegan diets were categorized by World Health
Organization publication with 30-35% absorption in zinc bioavailability [49].
Conclusion
According to this results, the dietary intake of vegetarian in college students
were able to meet the macronutrient recommendations of DRIs. However, it is
advised for vegetarians to include dietary supplement of n-3 PUFA, calcium, vitamin
D, and vitamin B12 in their diets. Based on this study, the omnivore college students
might also need to include more nutrient dense food in their diet and some dietary
supplement like n-3 PUFA, calcium, and vitamin D. Further research with bigger
sample and nutritional status analyses are needed to confirm the effect of nutrient
intake on nutritional status in college students.
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