Download Nutrient intake and iron status of Australian male vegetarians

European Journal of Clinical Nutrition (1999) 53, 189±194
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Nutrient intake and iron status of Australian male vegetarians
AK Wilson1 and MJ Ball1*
School of Nutrition and Public Health, Deakin University, Melbourne, Australia
Objective: The study was designed to investigate the iron intake and status of Australian, male vegetarians aged
between 20 and 50 y.
Design: Cross-sectional comparison of male vegetarians and age=sex matched omnivores.
Setting: Free-living community subjects.
Subjects: 39 ovolactovegetarians, 10 vegans and 25 omnivores were recruited by local advertisement.
Outcome measures: A 12-d semiquantitative dietary record to assess iron and zinc intake. Iron status was
assessed by measurement of serum ferritin and haemoglobin concentrations.
Results: Mean (s.d.) daily iron intakes of both the ovolactovegetarians (20.4 (7.7) mg=d) and vegans (22.9 (6.2)
mg=d), were signi®cantly higher than the omnivores' intake of 15.8 (4.5) mg=d. Ovo-lactovegetarians and
vegans had signi®cantly (P < 0.001 and P < 0.05, respectively) lower serum ferritin concentrations than
omnivores: mean (s.d.): 64 (46.9), 65 (49.9) and 121 (72.5) ng=ml, respectively. Signi®cantly more ovolactovegetarians and vegans than omnivores had serum ferritin concentrations below 25 ng=ml and below 12 ng=ml
(P < 0.05). A higher proportion of omnivores had concentrations above 200 ng=ml (P < 0.05). The differences in
serum ferritin concentrations between the vegetarians and omnivores remained signi®cant even after exclusion of
iron supplement users.
Conclusion: Australian male vegetarians had iron intakes higher than those of omnivores and above
recommended levels, but their iron status was signi®cantly lower.
Sponsorship: Deakin University.
Descriptors: dietary iron; ferritin; iron status; vegetarianism
Introduction
Compared to omnivores, vegetarians have been reported to
have a lower incidence of a number of chronic diseases,
such as coronary heart disease (Havala & Dwyer, 1993),
diabetes, osteoporosis, arthritis, kidney stones and some
cancers (Dwyer, 1988). In addition, vegetarians generally
have lower blood pressure and body weight closer to
desired levels (Dwyer, 1988). These factors may be attributed to several dietary differences between omnivores and
vegetarians and also to many positive lifestyle practices of
vegetarians. As demonstrated by Burr and Butland (1988) it
is dif®cult to determine which aspects of the vegetarian diet
and lifestyle are protective. However, despite these health
bene®ts, the vegetarian diet has been associated with
vitamin B12 , ribo¯avin, vitamin D, calcium, zinc and iron
de®ciencies (Gibson, 1990; Dwyer, 1991; Havala &
Dwyer, 1993).
Owing to the physiological importance of iron and zinc,
the adequacy of vegetarian diets with respect to both
minerals has been the focus of study by several investigators (Latta & Liebman, 1984; Levin et al, 1986; Alexander
et al, 1994; Donovan & Gibson, 1996).
Dietary iron intake is a concern in vegetarians, as animal
foods are the exclusive source of haem iron, which is the most
bioavailable form of dietary iron with an absorption ef®ciency
of 15 ± 25% (Monsen et al, 1978; Winston, 1994). Non-haem
iron, which is found in fruit, vegetables, cereals, dairy
products and eggs (Monsen et al, 1988; Winston, 1994), is
*Correspondence: M Ball, School of Nutrition and Public Health, Deakin
University, Melbourne, Australia.
Received 22 August 1998; revised 28 September 1998; accepted 12
October 1998.
the only form of iron in vegetarian diets and is less bioavailable. In addition, food components that may limit the bioavailability of non-haem iron are typically present in high
amounts in vegetarian diets. These components include
phytates (Oberleas & Harland, 1981; Hallberg et al, 1987;
Ferguson et al. 1989), phenolic compounds (Brune et al,
1989), calcium (Freeland Graves et al, 1980; Gibson, 1990)
and ®bre (Freeland Graves et al, 1980).
The Australian Recommended Daily Intake (RDI) for iron
is 12 ± 15 mg for adolescents and menstruating women, and
7 mg for men and post-menopausal women (NHMRC, 1991).
However, owing to the variation in iron bioavailability of
different foods and in diets with various food combinations
(Winston, 1994), assessment of adequacy of iron intake in
terms of meeting RDIs is a dif®cult task and subject to
considerable error. The daily zinc requirement for adults has
been set in the range of 6 ± 12 mg (NHMRC, 1991). In the
Australian National Nutrition Survey (McLennan & Podger,
1995), the mean daily intake for adult men in Victoria
(determined from diet recall and food frequency questionnaires (FFQ)) was 16.8 mg iron and 14.4 mg zinc.
Several studies have been carried out to assess the
adequacy of vegetarian iron intake. However, few have
used diet records over a 12 to 14-d period, considered
necessary to reliably determine iron intake (Basiotis et al,
1987). One such study, conducted by Alexander and
colleagues in New Zealand, found the iron intake of both
male and female vegetarians to be signi®cantly higher than
that of omnivores (Alexander et al, 1994). This difference
was particularly evident in males. These ®ndings are
consistent with studies of Kelsay et al (1988) and others
(Levin et al, 1986; McEndree et al, 1983).
Studies by Alexander et al (1994) and others (Faber et al,
1986; Helman & Darnton Hill, 1987) assessed iron status by
Nutrient and iron status of vegetarians
AK Wilson and MJ Ball
190
measurement of the serum ferritin concentration, which is a
measure of body iron status (Pilon et al, 1981). Results
showed both male and female vegetarians to have signi®cantly lower serum ferritin levels than omnivores. In other
studies, a signi®cant difference in iron status between vegetarians and omnivores was not shown when different methods
of iron status assessment were used that are considered to have
low sensitivity relative to the serum ferritin measurement
(Latta & Liebman, 1984; Levin et al, 1986).
A number of studies (Freeland Graves et al, 1980; Levin et
al, 1986) have also assessed both the adequacy of vegetarian
zinc intake and zinc status. Using a 24 h recall and FFQ as the
diet assessment methods, results indicate there are no differences in vegetarian and omnivore zinc intake. However, a
study of adolescents by Donovan and Gibson (1996) using 3 d
weighed records shows a higher probability estimate of
inadequacy for zinc and iron. Kadrabova et al (1995) also
found plasma zinc concentration in vegetarians to be signi®cantly lower than in omnivores, although they provided no
dietary data and plasma zinc may not be a particularly reliable
measure of zinc status.
Interestingly, the small study by Alexander et al (1994)
raised particular concern for the iron status of vegetarian
men, as a signi®cant proportion had serum ferritin levels
below 12 ng=ml, indicating storage iron depletion. Despite
these results, and the increasing incidence of male vegetarianism in Australia, most concern is typically given to
women, with very little focus on men. In fact there has been
only one published Australian study investigating iron
status of vegetarian males (Helman & Darnton Hill,
1987), and none speci®cally addressing the adequacy of
iron and zinc intake.
The aim of this study was to assess the iron and zinc
intake and iron status of healthy Australian male adult
vegetarians using a 12 d semiquantitative food record and
serum ferritin and haemoglobin measurements and to
compare the results with age- and sex-matched omnivores.
Methods
Fifty vegetarians aged 20 ± 50 y were recruited in the
Melbourne Metropolitan area, by advertisement in magazines, restaurants and health food shops. Twenty-®ve
healthy omnivores, of the same age and similar body
mass index (BMI) to the vegetarian subjects, were also
recruited as `friend controls' of the vegetarians and by
advertisement. For the purpose of this study, an ovolactovegetarian was de®ned as someone who never consumed
red meat and consumed chicken or ®sh no more than once a
week; a vegan was de®ned as someone who ate no meat,
eggs or dairy products. Unless otherwise speci®ed, `vegetarian' includes both of these groups. An omnivore was
someone who consumed red meat. Subjects were included
only if they had been practising the particular diet for at
least 6 months, were non-smokers, were in good health and
were not using any medications regularly. Deakin University Ethics Committee approved this study, and each
participant gave written informed consent.
At an initial meeting, all subjects completed a questionnaire on their dietary habits, use of supplements and
medications, previous de®ciencies related to diet, smoking
habit and usual levels of exercise. Subjects were given
detailed instructions on how to complete accurately a
validated, 12 d semiquantitative food record (Edington et
al, 1988) on either 12 consecutive days or from three
sequences of 4 consecutive days followed by a few days
rest but overall including 3 ± 4 weekend days. The importance of the 12 d recording period being representative of
their normal eating patterns was explained to subjects. A
set of electronic scales was provided for each subject to
weigh food. In situations where weighing of food was not
possible, subjects were instructed to estimate food portion
sizes by referring to photographs in the food dairy.
After completion of the diary, it was examined to clarify
any queries. A fasting, venous blood sample was taken for
estimation of serum ferritin and haemoglobin concentration. Weight and height were measured on a set of `Seca'
digital scales, with minimal clothing and no shoes, and
body mass index (BMI: weight (kg)=height (m2 )) was
calculated. Waist and hip circumference were measured
to the nearest millimetre using a standard, non-extensible
measuring tape, and the waist=hip ratio was calculated.
Sitting systolic and diastolic blood pressure were determined using an oscillomate 93 (Wallace Instruments Pty
Ltd, Australia).
Haematological measurements
Haemoglobin was measured immediately using an electronic counter (HemoCue AB: Mallinckrodt Medical Pty Ltd,
Nottinghill, Australia). Serum was separated by centrifugation at 4 C for 15 min (3000 rpm) after allowing the blood
to clot at room temperature for 1 h. Serum samples were
stored at 7 20 C for later analysis of serum ferritin. Serum
ferritin measurements were performed at the `Inter-Lab'
pathology laboratory by a two-site chemiluminometric
immunoassay, using a Ciba Corning Automated Chemiluminescence System (ACS: 180 Australian Diagnostics
Corporation Pty Ltd, Ciba Corning Diagnostics Corp,
Scoresby).
Diet analysis
The food and beverage intakes recorded on the 12 days by
each participant were entered into the dietary analysis
program `Diet-3', whose data is based on Australian Food
Composition Tables (Xyris 1987 ± 91, version 3.22). When
composite foods eaten were not present on the database,
recipes were entered.
Statistical analysis
All statistical analyses were performed using the Statistical
Package for Social Sciences version 6.0 (SPSS Pty Ltd,
Chicago, IL, USA). Nonparametric analyses using the Kruskal ± Wallis one-way ANOVA were performed to determine
differences between omnivores, ovolactovegetarians and
vegans for nutrient intake and haematological measurements.
The Mann ± Whitney U-test was then performed with the
Bonferroni adjustment (Matthews & Farewell, 1988) to
identify which groups had signi®cant differences. Multiple
regression analyses were performed to assess the relationship
between dietary variables and serum ferritin concentrations.
The Fisher exact test was used to demonstrate whether the
three dietary groups were different with respect to having
values below and above certain limits.
Results
The vegetarian group that completed the study consisted of
39 ovolactovegetarians and 10 vegans. The ovolactovegetarians and vegans had been following their dietary
Nutrient and iron status of vegetarians
AK Wilson and MJ Ball
practices for a mean of 11 y (range 0.5 ± 44) and 6 y (range
1.5 ± 14), respectively. The 25 omnivore controls who
participated did not differ signi®cantly from either the
ovolactovegetarians or vegans with respect to age,
BMI, waist=hip ratio, and blood pressure (Table 1),
although their weight was higher than the ovolactovegatarians.
The daily nutrient intakes of the three dietary groups are
shown in Table 2. While total energy intake was similar for
omnivores, ovolactovegetarians and vegans, the vegetarians derived a signi®cantly lower proportion of their energy
from protein compared to omnivores. A much higher
proportion of energy derived from carbohydrate compensated for this. Total fat intake and percentage of energy
derived from fat were lower for ovolactovegetarians than
for omnivores, as was saturated fat intake, with vegans
consuming less than half the saturated fat of omnivores.
The vegetarians consumed a higher percentage of total fat
as polyunsaturated fat. Cholesterol intake was signi®cantly
different between all three dietary groups, with the omnivores consuming the most and the vegans the least. Dietary
®bre was signi®cantly higher in vegetarians than in omnivores. Mean calcium intakes did not differ signi®cantly and
were above the Australian RDI of 800 mg=d. Vitamin C
intake of all groups was also well above recommended
levels, with the vegans consuming signi®cantly greater
amounts, with a mean of nine times the Australian RDI
of 40 mg=d (NHMRC, 1991).
The mean daily iron and zinc intakes of omnivores,
ovolactovegatarians and vegans are shown in Table 3. Ovolactovegetarians and vegans had signi®cantly higher mean
daily iron intakes than omnivores (P < 0.05 and P < 0.01,
respectively). All the men had an intake above the RDI for
men of 7 mg=d, the mean intakes for omnivores, ovolactovegetarians and vegans being 226%, 291% and 320% of
RDI, respectively. Zinc intakes of the three groups were not
signi®cantly different, with a high proportion of the omnivores, ovolactovegetarians and vegans having intakes
below the Australian RDI of 12 mg=d (40%, 64% and
70%, respectively).
The dietary sources of iron of the omnivores and
vegetarians are indicated in Figure 1. Both ovolactovegetarians and vegans obtained their iron predominantly from
cereals, vegetables, fruits, seeds and nuts. Cereals were also
a main source of dietary iron for omnivores, but, in contrast
to vegetarians, omnivores obtained a high proportion of
iron from meat and meat products.
Serum ferritin and haemoglobin concentrations (Table
4) were signi®cantly lower in ovolactovegetarians and
vegans compared to those in omnivores (P < 0.001 and
P < 0.05, respectively). The distribution of serum ferritin
levels is shown in Figure 2. Differences between the three
dietary groups were signi®cant, with more ovolactovegetarians and vegans than omnivores having serum ferritin
concentrations below 25 ng=ml (P < 0.05). One ovolactovegetarian aged 23 years and two vegans aged 41 and 36
Table 1 Physical characteristics of omnivores, ovolactovegetarians and vegans; mean (s.d.)
Group
n
Omnivores
25
Ovolactovegetarians
39
Vegans
10
Age
(y)
Weight
(kg)
Height
(cm)
BMI
Systolic
BP
Diastolic
BP
32.7
(8.8)
33.3
(8.2)
31.0
(5.6)
79.8
(9.5)
70.6*
(11.2)
74.1
(14.2)
179.9
(5.9)
179.5
(7.9)
180.5
(8.0)
23.8
(2.7)
21.8
(2.5)
22.6
(3.1)
124.8
(15.7)
115.3
(12.6)
119.3
(9.5)
75.8
(8.4)
72.4
(12.8)
73.5
(9.6)
*Signi®cantly different from omnivores, P < 0.001.
Table 2 Comparison of daily nutrient intakes of male ovolactovegetarians vegans and omnivores; mean values or mean (s.d.)
Nutrient
Energy (MJ)
[Kcal]
Protein (g)
% total energy
Fat (g)
% total energy
Carbohydrate (g)
% total energy
Polyunsaturated fat (g)
% total fat
Monounsaturated fat (g)
% total fat
Saturated fat (g)
%total fat
Cholesterol (mg)
Dietary ®bre (g)
Sodium (g)
Calcium (mg)
Vitamin C (mg)
Vitamin A (mg)
Omnivore (n=25)
Ovo-lactovegetarians
(n=39)
Vegans
(n=10)
11.0 (1.9)
[2632]
108 (17.2)
17.3
98.3 (31.8)
33.5
291 (77.4)
44.9
14.6 (8.4)
16.1
34.6 (11.7)
38.1
41.3 (13.3)
45.8
289 (96)
26.3 (7.7)
3.4 (0.7)
961 (263)
151 (93)
981 (326)
10.5 (2.4)
[2548]
80 (16.4)b
15.5b
81.8 (28.1)a
28.2a
357 (92)
54.5b
19.7 (8.6)
27.5b
28.9 (15.0)a
38.3c
24.2 (9.1)b
35.0bd
102 (67)bc
49.8 (15.9)b
2.5 (0.8)b
899 (284)
218 (178)c
1266 (602)
11.6 (2.7)
[2815]
81 (24.3)a
12.4b
88 (37.6)
28.0
413.4 (96.8)
59.1b
27.2 (16.0)
31.8b
35.4 (16.3)
44.1a
18.3 (7.5)b
24.1b
22 (28)b
63.8 (14.6)b
1.7 (9.5)b
911 (471)
360 (179)a
1661 (497)b
Signi®cantly different from omnivores (aP < 0.01, bP < 0.001).
Signi®cantly different between ovolactovegetarians and vegans (cP < 0.05, P < 0.01, eP < 0.001).
a,b
c,d,e
191
Nutrient and iron status of vegetarians
AK Wilson and MJ Ball
192
Table 3 Daily intakes of iron and zinc of omnivores, ovolactovegetarians and vegans. Mean intakes for iron are given as a percentage of Australian RDI.
The proportion of subjects with zinc intakes below the Australian RDI is also given
Iron intake (mg=d)
Zinc intake (mg=d)
Group
n
Mean (s.d.)
Range
% of RDI
Mean (s.d.)
Range
< RDI (%)b
Omnivores
Ovo-lactovegetarians
Vegans
25
39
10
15.8 (4.5)
20.4 (7.7a
22.9 (6.2)b
8.2 ± 27.5
8.5 ± 42.3
15.2 ± 35.1
226
291
320
12.7 (2.4)
12.0 (4.4)
12.6 (3.8)
9.3 ± 16.9
5.8 ± 26.1
7.4 ± 18.1
40
64
70
a
The mean iron intake as a percentage of the Australian RDI for iron of 7 mg=d.
The percentage of subjects below the Australian RDI for zinc of 12 mg=d.
a,b
Signi®cantly different from omnivores (aP < 0.05, bP < 0.01).
b
Figure 1 Serum ferritin concentration (ng=ml) in vegetarians and omnivores.
years had serum ferritin concentrations below 12 ng=ml
(11, 8 and 10 ng=ml, respectively). All three subjects had
iron and vitamin C intakes well above Australian RDIs and
had not taken iron supplements, and the ovolactovegetarian
consumed ®sh and chicken once or twice a month. More
omnivores than vegetarians had serum ferritin concentrations above 200 ng=ml (P < 0.05).
Three subjects, two ovolactovegetarians and one vegan,
had haemoglobin concentrations (125, 129 and 120 g=l)
below the reference range of 130 ± 150 g=l: one had a serum
Figure 2 Dietary sources of iron in omnivores (j) and vegetarians (u).
ferritin concentration of 153 ng=ml (in the normal range),
while the other two subjects had low concentrations.
Eight ovolactovegetarians and two omnivores were
either currently taking iron supplements or had taken
them in the previous two years. The serum ferritin concentrations of this group ranged from 24 to 117 ng=ml.
Twenty-one vegetarians (including 4 who also took iron
supplements) currently took a vitamin supplement that did
not contain iron. Additionally, 11 ovolactovegetarians consumed either ®sh a few times a year or chicken once or
twice a month (three of whom also took iron supplements).
After exclusion of all iron-supplement users, and of ovolactovegetarian ®sh=chicken eaters the serum ferritin levels
of omnivores remained signi®cantly higher than those of
the ovolactovegetarians (P < 0.001) and vegans (P < 0.01).
Multiple regression analysis showed there was no signi®cant correlation between age, alcohol, calcium, iron or
®bre intake and serum ferritin concentrations for the
vegetarians and omnivores. However, a highly signi®cant,
positive correlation was found between vitamin C intake
and serum ferritin concentrations (r 2 ˆ 0.52, P < 0.001).
Discussion
The adequacy of the vegetarian diet with respect to nutrient
and vitamin intake has been the focus of a number of
investigations. However, the present study is one of only
two Australian studies that we are aware of that have
assessed the adequacy of adult male vegetarian iron
Nutrient and iron status of vegetarians
AK Wilson and MJ Ball
193
Table 4 Subjects with serum ferritin in certain ranges and haemoglobin (g=L) concentrations in omnivores, ovo-lactovegetarians and vegans
Group
n
Mean
(s.d.)
Omnivores
Ovo-lactovegetarians
Vegans
25
39
10
121 (73)
64 (47)c
65 (50)b
HB (g=l)
Range
Ferritin
< 12 ng=ml n (%)a
Ferritin
< 25 ng=ml n (%)a
Ferritin
> 200 ng=ml n (%)a
Mean (s.d.)
Range
44 ± 313
11 ± 238
8 ± 137
0 (0)
1 (3)
2 (25)
0 (0)
8 (20.5)b
3 (30)
5 (20)
1 (2.6)b
0 (0)b
173 (19)
140 (40)c
158 (28)b
144 ± 206
125 ± 195
129 ± 201
a
Number and percentage of subjects with serum ferritin in the stated range.
Signi®cantly different from omnivores (bP < 0.05, cP < 0.001).
c,d
status. Adequacy of iron intake was assessed using a
quantitative food record over an adequate period of time,
and serum ferritin and haemoglobin concentrations were
measured as an indication of iron status.
Iron intakes of both ovolactovegetarians and vegans
were signi®cantly higher than those of omnivores, with
all dietary groups having intakes well above the Australian
RDI of 7 mg=d. A study conducted by Alexander et al
(1994) on a vegetarian population in New Zealand consisting of 36 females and 14 males also found male vegetarian
iron intake to be above recommended levels and higher
than that of omnivores. The intakes (mean 20.4 mg=d and
20.2 mg=d, respectively), using the same dietary methodology, were very similar to those in our study. The differences in iron intake between vegetarians and omnivores are
consistent with those found by Kelsay et al (1988), who
compared iron intakes of Asian-Indian and American
vegetarian groups to an American omnivore group. Other
investigators ®nding similar results include Levin et al
(1986), who studied an Israeli population consisting of 92
vegetarians and 113 omnivores, and McEndree et al (1983),
who investigated a vegetarian group in Nebraska.
A common methodological feature of our study and the
studies conducted by Alexander et al (1994) and Kelsay et
al (1988) is that nutrient intakes were assessed using 12 d
and 14 d semiquantitative, diet records. This method of
dietary assessment has been shown by Edington et al
(1988) to have similar reliability to weighed food records,
which are considered the most precise method. As calculated by Bingham (1987), 12 days are required to record
individual, long-term iron intake within 10% of the mean.
In contrast, studies that used records over shorter periods of
3 ± 7 days (Latta & Liebman, 1984; Faber et al, 1986) have
not shown a difference in vegetarian and omnivore iron
intake.
Ovolactovegetarians obtained their dietary iron exclusively from non-haem iron sources such as fruits, vegetables, cereals, dairy products and eggs, while for vegans,
fruit, vegetables and cereals were the only iron source.
Although the amount of iron consumed was above the RDI,
the actual amount absorbed may be considerably lower,
owing to the low bioavailability of non-haem iron and food
components inhibiting absorption.
Iron status was thus measured and, as indicated by
serum ferritin concentration, was signi®cantly lower in
the vegetarians compared to the omnivores. Twenty-eight
per cent of vegetarians had serum ferritin levels below
25 ng=ml, which may indicate the beginning of iron storage
depletion (Bothwell et al, 1979). Furthermore, one ovolactovegetarian and two vegans had serum ferritin concentrations below 12 ng=ml, indicating depletion of storage iron
(Cook et al, 1992). Although these subjects' haemoglobin
levels were in the normal range, these storage levels might
prove insuf®cient to provide for periods of stress or an
episode of blood loss, and continued low availability of
iron may result in iron de®ciency. The fact that iron intakes
of all subjects with ferritin levels below 25 ng=ml were
similar to or higher than those of other vegetarians and
omnivores with ferritin concentrations in the normal range,
indicates inter-person variation in absorption. Intake of
ascorbic acid was well above recommended intakes for
these individuals, and this is relevant as absorption of nonhaem iron is enhanced by consumption of ascorbic acid in
the same meal (Cook & Monsen, 1977). However, overall
ef®ciency of non-haem iron absorption is dependent on a
balance between inhibiting components and ascorbic acid
intake (Hallberg & Rossander, 1982). Vegetarians whose
non-haem iron and ascorbic acid intakes are similar may
have different levels of serum ferritin. Young Chinese
Buddhist vegetarians have half the ferritin level of nonvegetarian fellow students, and this was at least partly
attributed to their high phytate and soy intake (Shaw et
al, 1995). The higher serum ferritin levels in omnivores can
easily be explained by the consumption of the more
ef®ciently absorbed haem iron.
Interestingly, one ovolactovegetarian who ate chicken
and ®sh a few times a year, and 20% of omnivores, had
serum ferritin concentrations above 300 ng=ml. Such high
levels may not be advantageous. In the Kuopio Ischaemic
Heart Disease Risk Factor Study (Salonen, 1993), a mean
serum ferritin concentration greater than 200 ng=ml was
found to correspond to a 2.2-fold increased risk of acute
myocardial infarction. Although these ®ndings have not
been con®rmed in subsequent American studies (and disagreement in results could be explained by differences in
serum cholesterol levels, as the risk due to elevated serum
ferritin decreases when cholesterol levels are below
5 mmol=l), it may indicate relative advantage for most
vegetarians.
Signi®cant differences in iron status between vegetarians and omnivores are consistent with ®ndings by Alexander et al (1994) and others (Faber et al, 21986; Helman
& Darnton Hill, 1987). Serum ferritin concentrations were
lower for both vegetarians and omnivores in the New
Zealand population compared to those in the Australian
study, despite similar iron intakes (Alexander et al, 1994).
This may be explained by the fact the Australian vegetarians consumed more vitamin C than the New Zealanders.
Helman and colleagues (Helman & Darnton Hill, 1987)
also studied an Australian vegetarian population (60 males
and 60 females) but did not consider males and females
separately, so comparison is not possible. There are, however, a number of papers reporting no signi®cant difference
in vegetarian and omnivore iron status. In some cases this
may be due to use of supplements by many subjects; for
example, in the study by Locong (1986), 50% of the
Nutrient and iron status of vegetarians
AK Wilson and MJ Ball
194
vegetarians studied (22 females and 14 males) ate ®sh=
poultry once a month and 61% took vitamin and mineral
supplements. Animal ¯esh enhances iron absorption by
stimulating the absorption of non-haem iron and providing
some haem iron (Hallberg et al, 1986). In other studies, the
method of iron status assessment used is less sensitive than
serum ferritin (Pilon et al, 1981). Latta and Leibman (1984)
assessed the iron status of 36 American male vegetarians by
determination of whole-blood hematocrit, plasma iron and
total iron binding capacity, and there can be poor iron status
when these parameters are normal.
As in previous studies (Freeland Graves et al, 1980;
Levin et al, 1980; Levin et al, 1986), zinc intakes in the
ovolactovegetarian, vegans and omnivores were found to
be similar. Dietary phytates (Oberleas & Harland, 1981),
calcium and insoluble ®bre (Freeland Graves et al, 1980)
inhibit zinc absorption, and the high content of these food
components and the exclusion of animal meats from the
vegetarian diet may lead to a low zinc status in vegetarians.
In the present study, a high proportion of subjects in all
three dietary groups had zinc intakes below the Australian
RDI of 12 mg=d. Therefore, consideration should be given
to measurement of zinc status in vegetarians who consume
large amounts of calcium and ®bre and phytate-rich foods
such as rye bread, apples, rice, oatmeal and wheat cereals
(Turnlund et al, 1984).
The present study demonstrates that vegetarians had
intakes of most macronutrients, minerals and vitamins
closer to Recommended Intakes than did omnivores, particularly with respect to quantity and type of fat intake,
sodium, antioxidant vitamin and ®bre intake. This may
provide health bene®ts, particularly with respect to coronary heart disease. However, more consideration needs to be
given to iron status in these men, even when their intake
appears to meet the RDI. In fact, the RDI may need to be
higher than 7 mg for male vegetarians. Attention should be
given to optimising non-haem iron absorption by education
about meal planning. Main meals containing non-haem iron
should be eaten in combination with foods high in ascorbic
acid while high phytate, phenolic and calcium foods should
generally be avoided at the same time.
Acknowledgements ÐWe thank Professor Andy Sinclair, Duo Li and Neil
Mann, RMIT for assisting in recruiting volunteers.
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