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Chapter 6
Vitamins
Chapter Objectives
1. Understand the importance of vitamins.
2. Define vitamins.
3. Explain how the dietary needs for vitamins are represented.
4. Learn the functions of water-soluble vitamins, effects on energy systems, their deficiency and toxicity symptoms,
their importance to sports performance, and vitamin-rich food sources and meal-planning tips.
5. Learn the functions of fat-soluble vitamins, their effects on energy systems, their deficiency and toxicity
symptoms, their importance to sports performance, and vitamin-rich food sources and meal-planning tips.
6. Recognize which vitamins or compounds have antioxidant properties.
7. Define phytochemicals.
Chapter Outline
I. What's the big deal about vitamins?
A. Without vitamins, the body could not function; as a result, vitamins are considered to be essential.
B. Some vitamins can be synthesized in the body.
C. Many vitamins are precursors for different processes, whereas others are critical for the development of
various compounds in the body.
D. Although it is clear that vitamins are crucial for body functions, less is known about the potential role
they play in improving or hindering sport performance.
E. Although the performance effect may not be proven, certain athlete populations are more prone to
nutrient deficiencies, thus justifying a greater emphasis on a specific vitamin or mineral.
F. This chapter will discuss the recommended intake levels for vitamins, antioxidants, and phytochemicals.
It will also present:
1. The functions of these nutrients.
2. Their effects on energy systems.
3. Their deficiency and toxicity symptoms.
4. Their importance to sport performance.
5. Food sources for these nutrients.
6. Meal-planning tips so athletes can meet their needs for these nutrients.
II. What are vitamins?
A. There are two classifications of vitamins: water soluble and fat soluble.
1. Water-soluble vitamins include the B vitamins, vitamin C, and choline.
a. Water-soluble vitamins dissolve in water.
b. They are transported easily in the blood.
c. They are turned over in the body; as a result, they are not stored in the body in
appreciable amounts. Therefore, regular intake is important.
d. Utilization of water-soluble vitamins occurs on an as-needed basis; excess amounts are
excreted in the urine.
2. Fat-soluble vitamins include vitamins A, D, E, and K.
a. Fat-soluble vitamins do not dissolve easily in water.
b. They require dietary fat for intestinal absorption and transport in the bloodstream.
c. They are stored in the body primarily in fat tissue and the liver. They are also stored in
other organs, although in smaller amounts. When taken in excess, stored levels of fatsoluble vitamins can build up and become toxic to the body.
d. Dietary intake from foods rarely causes a toxic buildup, but intake via high-dosage
supplements can quickly and easily build these vitamins to toxic levels.
B. Water- and fat-soluble vitamins are vital to human health. An emphasis should be placed on food
sources of vitamins, rather than on supplements. High-vitamin foods should be consumed on a daily basis.
III. How are the dietary needs for vitamins represented?
A. The Dietary Reference Intakes (DRIs) include several ways to quantify nutrient needs or excesses of
vitamins and minerals.
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B. Detailed descriptions of the different DRI categories are included in Chapter 1.
C. Each vitamin may have one or more of the DRIs, depending on availability of current research data
(refer to Table 6.1).
IV. What are the water-soluble vitamins?
A. Water-soluble vitamins include the B-complex vitamins (thiamin, riboflavin, niacin, B 6, B12, folate,
biotin, and pantothenic acid), choline, and vitamin C.
1. They are involved in many different processes within the body. They act as coenzymes, and are
critical for energy production, especially during exercise.
2. Water-soluble vitamins can be obtained naturally from a large variety of food sources, as well
as from vitamin-fortified foods and beverages.
3. To maximize the benefit of eating foods rich in the B-complex and C vitamins, foods should be
eaten raw or cooked for short periods of time. The exception to this rule is any meat product,
which should be cooked thoroughly.
4. Foods rich in water-soluble vitamins should be consumed on a daily basis.
B. Thiamin (Vitamin B1)
1. Functions
a. Plays a major role in energy production.
b. It is important for developing and maintaining a healthy nervous system.
c. A component of the coenzyme thiamin pyrophosphate converts pyruvate into acetyl
CoA, which then enters into the Krebs cycle during aerobic energy production.
d. Plays a role in the conversion and utilization of glycogen for energy, as well as the
catabolism of branched chain amino acids.
2. RDA/AI for thiamin
a. 1.2 milligrams for males
b. 1.1 milligrams for females
c. The RDA is based on the notion that humans need approximately 0.5 milligrams of
thiamin per 1,000 calories ingested daily. Therefore, thiamin requirements escalate with
increased calorie intake.
d. Thiamin is also critical for the proper metabolism of carbohydrates; as carbohydrate
intake increases, so does the requirement for thiamin.
3. Complications of thiamin deficiency
a. Typically due to an athlete consuming very few calories or having a diet composed
mainly of processed foods.
b. Signs and symptoms of thiamin deficiency include decreased appetite, mental
confusion, headaches, fatigue, muscle weakness, nerve degeneration, and pain in the calf
muscles.
c. If a severe deficiency is left untreated for as little as 10 days, the disease Beriberi can
develop, which can lead to damage to the heart and nervous system.
d. With regard to performance, studies have found that athletes with low intakes of
thiamin and other water-soluble vitamins over the course of 11 weeks suffer decreases in
maximal work capacity, peak power, and mean power output.
4. The risk for thiamin toxicity is low; therefore, no upper limit has been set for thiamin intake.
5. Foods rich in thiamin
a. Thiamin is found in a variety of foods including whole grains, legumes, wheat germ,
nuts, pork, and fortified foods, such as refined flours, grains, and breakfast cereals.
b. Refer to Figure 6.1.
6. Suggestion for a thiamin-rich meal or snack
a. Breakfast: One packet of instant oatmeal, made with 8 oz soy milk and topped with 1/4
cup sunflower or pumpkin seeds
b. Total thiamin content = 0.768 milligrams
7. Thiamin supplementation
a. Research on the ergogenic effects of thiamin supplementation is limited and has
provided inconclusive results.
b. The focus should first be on nutrient-rich foods and then a supplement, if indicated.
C. Riboflavin (vitamin B2)
1. Functions
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a. Highly involved in the aerobic production of energy [i.e., adenosine triphosphate
(ATP)] from carbohydrates, proteins, and fats.
b. It is a component of two coenzymes—flavin mononucleotide and flavin adenine
dinucleotide. These enzymes are involved in the transport of electrons to the electron
transport chain during aerobic energy production at rest and during exercise.
2. RDA/AI for riboflavin
a. 1.3 milligrams for males
b. 1.1 milligrams for females
3. Complications of riboflavin deficiency
a. Riboflavin deficiency is recognized by symptoms such as red lips, cracks at the corners
of the mouth, a sore throat, or an inflamed tongue.
b. In athletics, a riboflavin deficiency may contribute to poor performance.
4. No upper limit has been set for riboflavin.
5. The following foods are rich in riboflavin:
a. Milk, yogurt, bread, cereal products, mushrooms, cottage cheese, and eggs are all good
sources of riboflavin. Similar to thiamin, bread and cereal products in the United States
are fortified with riboflavin.
b. Refer to Figure 6.2.
6. Suggestion for a riboflavin-rich meal or snack:
a. Salad-bar creation: 2 cups of romaine lettuce with 1/2 cup each of mushrooms, carrots,
and cottage cheese, and 2 T of almonds
b. Total riboflavin content = 0.661 milligrams
7. Riboflavin supplementation
a. Minimal research has been conducted on the performance effects of riboflavin
supplementation.
b. More research is warranted to make a recommendation on whether athletes require
more riboflavin than the current RDA.
c. Daily riboflavin needs can typically be met through a balanced and calorically
adequate diet.
D. Niacin (vitamin B3) = nicotinic acid and nicotinamide
1. Functions
a. Highly involved in energy production and mitochondrial metabolism; thus it affects
muscular and nervous system function.
b. Niacin is a component of two coenzymes that are important for the anaerobic and
aerobic energy systems: nicotinamide adenine dinucleotide (NAD+) and nicotinamide
adenine dinucleotide phosphate (NADP+).
2. RDA/AI for niacin
a. 16 milligrams for males
b. 14 milligrams for females
c. Niacin is obtained through the diet, but it can also be formed within the body from the
amino acid tryptophan. Therefore, the RDA refers to niacin equivalents (NE).
d. For foods rich in tryptophan, 60 milligrams of tryptophan is equivalent to 1 milligram
of niacin.
3. Complications of niacin deficiency
a. Signs and symptoms of niacin deficiency include loss of appetite, skin rashes, mental
confusion, lack of energy, and muscle weakness.
b. If the deficiency is left untreated, the disease pellagra develops.
4. Symptoms of niacin toxicity
a. The upper dietary limit is 35 milligrams per day.
b. Common side effects of high niacin intake include flushing of the face, arms, and
chest; itchy skin rashes; headaches; nausea; glucose intolerance; blurred vision; and
ultimately, liver complications.
c. Doses several times the RDA are used medicinally for lowering low-density
lipoprotein (LDL) cholesterol and raising high-density lipoprotein (HDL) cholesterol;
must be under physician care.
5. Foods rich in niacin
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a. Refined flours, grains, and cereals are fortified with niacin.
b. Other dietary sources include protein-rich foods such as beef, poultry, fish, legumes,
liver, and seafood, as well as whole-grain products and mushrooms.
c. Refer to Figure 6.3.
6. Suggestion for a niacin-rich meal or snack
a. Dining out—Italian: Chicken Marsala (4 oz chicken in 1 cup mushroom sauce) on 2
cups spaghetti
b. Total niacin content = 24 milligrams
7. Niacin supplementation
a. Recent research reviews have concluded that well-nourished athletes do not benefit
from niacin supplements.
b. Supplements are not recommended because high doses of niacin can affect fat
metabolism and increase blood flow to the skin.
Author Note: Discuss why many sports beverages, bars, and other supplements are fortified with thiamin, riboflavin,
and niacin. What are the pros and cons of this fortification?
E. Vitamin B6 = pyridoxine, pyridoxal, pyridoxamine, pyridoxine phosphate, pyridoxal phosphate, and
pyridoxamine phosphate
1. Functions
a. B6 is a component of more than 100 enzymes, some of which facilitate the breakdown
of glycogen for energy as well as gluconeogenesis in the liver, the synthesis of amino
acids via transamination, the conversion of tryptophan to niacin, the formation of
neurotransmitters, the production of the red blood cells' hemoglobin ring, and the
production of white blood cells.
b. A dietary protector against heart disease; it decreases blood levels of homocysteine
(refer to Figure 6.4).
2. RDA/AI for vitamin B6
a. The RDA for men and women aged 19 to 50 is 1.3 milligrams.
b. Because of the role of vitamin B6 in protein metabolism, requirements are based on
protein intake. Individuals following a high-protein diet may need to consume more
vitamin B6.
3. Complications of vitamin B 6 deficiency
a. Deficiencies in vitamin B6 in male and female athletes are rare.
b. Deficiency usually explained by low energy intake and poor food choices.
c. Symptoms include nausea, impaired immune function (due to low numbers of white
blood cells), convulsions, depression (related to the improper functioning of
neurotransmitters), skin disorders, mouth sores, weakness, and anemia (due to low levels
of red blood cell production).
4. Symptoms of vitamin B6 toxicity
a. The upper limit for vitamin B6 is 100 milligrams per day.
b. Irreversible nerve damage can occur at levels of 1,000 to 2,000 milligrams per day.
5. Foods rich in vitamin B6
a. The richest sources include high-protein foods such as beef, poultry, fish, and eggs.
b. Other significant sources include whole grains, brown rice, wheat germ, white
potatoes, starchy vegetables, fortified soy-based meat analogs, and bananas.
c. Refer to Figure 6.5.
6. Suggestion for a meal or snack rich in vitamin B 6
a. Lunch: Egg-salad sandwich on whole-wheat bread and a banana
b. Total vitamin B6 content = 0.834 milligrams
7. Vitamin B6 supplementation
a. Current research on the athletic performance benefits of vitamin B6 supplementation is
equivocal.
b. More research is warranted to determine the exact changes in vitamin B 6 metabolism
during short- and long-duration exercise to establish recommendations for
supplementation during training or competition.
F. Vitamin B12 (cobalamin)
1. Functions
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a. Plays a role in the health and performance of the nervous and cardiovascular systems,
the growth and development of tissues, and energy production.
b. Critical for folate metabolism, which in turn relates to DNA synthesis and tissue
growth.
c. Adequate intakes prevent the onset of pernicious anemia.
d. Involved in preparing fatty-acid chains to enter the citric acid cycle, thus facilitating
energy production.
e. Lowers homocysteine levels in the blood, thus aiding in the prevention of heart disease
(refer Figure 6.4).
2. RDA/AI for vitamin B12
a. 2.4 micrograms for adults aged 19 to 50 years
b. Older adults have a decreased ability to absorb B 12. The synthetic form of B12 can be
absorbed more readily than food sources for these individuals; therefore, they should
focus on incorporating fortified foods and supplements into their daily diet.
c. Refer to Fortifying Your Nutrition Knowledge on page 162.
3. Complications of vitamin B 12 deficiency
a. Caused by either impaired absorption or decreased intake.
b. Individuals following a vegetarian, especially a vegan, diet will need to consume
fortified foods or take daily supplements to avoid deficiency problems.
c. Vitamin B12 deficiency can result in neurological problems and pernicious anemia.
d. A deficiency of vitamin B12 can lead to increased homocysteine levels and a greater
risk for heart disease.
4. Symptoms of vitamin B12 toxicity: Because no recognized detrimental effects from high doses
of B12 have been recognized, an upper limit has not been set.
5. Foods rich in vitamin B12
a. Naturally found only in animal products such as meats, dairy products, and eggs (refer
to Figure 6.6).
b. For vegetarians and vegans, fortified foods include breakfast cereals, soy milk, and
other soy-based products.
6. Suggestion for meal or snack rich in vitamin B 12
a. Dinner: 3-oz slice of meatloaf with 3/4 C mashed potatoes, 1 1/4 cups salad, and 12 oz
skim milk
b. Total vitamin B12 content = 2.45 micrograms
7. Vitamin B12 supplements
a. Vegetarian or vegan athletes may need supplemental B 12 from fortified vegetarian
foods, soy products, or multivitamins.
b. Masters or elderly athletes may also need B 12 supplements if they have atrophic
gastritis and/or low levels of intrinsic factor.
c. Those with diagnosed pernicious anemia will have enhanced performance after
consuming higher doses of B12.
d. Healthy athletes consuming a balanced diet may not benefit from vitamin B 12
supplements.
G. Folate: Folate is found in foods; folic acid is found in supplements.
1. Functions
a. It is critical for DNA synthesis and cell division; thus it plays an important role in the
growth and development of a fetus.
b. Adequate folate intake has been recognized as being key in the prevention of neural
tube defects during pregnancy.
c. Aids in the maturation of red blood cells and the repair of tissues (prevents the
development of megaloblastic, macrocytic anemia).
d. Helps to lower levels of homocysteine in the blood, thus potentially lowering the risk
for heart disease.
2. RDA/AI for folate
a. 400 micrograms per day for adult males and females
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b. Expressed in Dietary Folate Equivalents (DFE). One DFE equals 1 microgram of
folate from food, 0.6 micrograms of folic acid in fortified foods, or 0.5 micrograms of
folic acid in supplements taken on an empty stomach.
3. Complications of folate deficiency
a. If a mother consumes suboptimal levels of folate during pregnancy, the risk of fetal
neural tube defects increases considerably.
b. Low folate levels cause a change in DNA, affecting various cells, such as those in the
lining of the intestines, and causing absorption problems and chronic diarrhea.
c. Low folate levels may impair white blood cell development, contributing to poor
immune function.
d. Megaloblastic anemia (clarify reason for anemia—could be caused by a deficiency of
folate or vitamin B12).
e. Helps to lower levels of homocysteine in the blood, thus potentially lowering the risk
for heart disease.
4. Symptoms of folate toxicity (upper limit has been established for adults at 1,000 micrograms).
a. Toxicity is rare because ingesting high levels of folate in foods is difficult, and excess
folate is excreted in the urine.
b. High levels of folate can hide symptoms of vitamin B 12 deficiency, thus an UL has
been set for folate.
5. Foods rich in folate
a. Folate-rich foods include many plant-based products, such as dark green leafy
vegetables, strawberries, oranges, legumes, nuts, brewer's yeast, and fortified grains (refer
to Figure 6.7).
b. Folate is added to fortified grains and flours (mandated in 1996 and went into effect in
1998).
6. Suggestion for a folate-rich meal or snack
a. Refer to Black-Eyed Peas with Chinese Greens recipe on page 165.
b. Refer to Figure 6.7.
7. Folate supplements
a. A multivitamin can be used to ensure adequate intake.
b. To date, no studies suggest that extra folate increases exercise capacity
Author Note: Develop meal plans for special-population athletes (masters, vegetarian, and pregnant) with adequate
quantities of the vitamins that are of particular concern for these groups.
H. Biotin
1. Functions
a. Plays a role in synthesizing DNA for healthy cell development and energy production
for endurance activities.
b. Cofactor for several carboxylase enzymes involved in the metabolism of
carbohydrates, proteins, and fats.
c. Biotin also helps produce energy by facilitating gluconeogenesis.
2. RDA/AI for biotin
a. Very little research exists on the biotin requirements for a healthy adult. Therefore, no
RDA has been set.
b. Adequate Intake level for adults is 30 micrograms per day.
3. Complications of biotin deficiency
a. Rare, because so little is required.
b. Some documented signs and symptoms of biotin deficiency include fatigue,
depression, nausea, dermatitis, and muscular pains.
4. Symptoms of biotin toxicity: Biotin appears to be safe even at high levels, so no upper limit has
been set.
5. Foods rich in biotin
a. Legumes, cheese, egg yolks, nuts, and green leafy vegetables
b. Biotin content has not been determined for most foods, and therefore is not listed on
most food composition charts.
6. Suggestion for a biotin-rich meal or snack
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a. Breakfast: 3 scrambled eggs with 1/4 cup shredded cheddar cheese and 2 T peanut
butter on 1 slice of whole wheat toast
b. Total biotin content = 57 micrograms
7. Biotin supplements
a. Very little research has been conducted on biotin and exercise performance.
b. Because no toxic level has been detected, supplemental biotin may not be harmful to
health or performance, but it also may not be necessary.
I. Pantothenic acid
1. A component part of coenzyme A, a molecule critical for the passage of metabolic
intermediates from fat, carbohydrate, and protein metabolism into the citric acid cycle.
2. RDA/AI for pantothenic acid
a. No RDA has been set for pantothenic acid.
b. Adequate Intake is set at 5 milligrams per day for adults aged 19 to 50 years.
3. Complications of pantothenic acid deficiency
a. Signs and symptoms include fatigue, sleep disturbances, impaired coordination,
nausea, hypoglycemia, and muscle cramps.
b. Deficiencies are very rare
4. Symptoms of pantothenic acid toxicity: No upper limit has been set.
5. Foods rich in pantothenic acid
a. Beef, poultry, fish, whole grains, dairy products, legumes, potatoes, oats, and tomatoes
(refer to Figure 6.8)
b. Fresh and whole foods; freezing, canning, processing, and refining foods decreases the
foods' pantothenic acid content considerably.
6. Suggestion for a meal or snack rich in pantothenic acid
a. Lunch: Baked potato topped with 3/4 cup garbanzo beans, 1/4 cup salsa, and 2 T
melted cheese, and an 8 oz glass of skim milk
b. Total pantothenic acid content = 2.4 milligrams
7. Pantothenic acid supplements
a. Deficiencies are rare, therefore supplementation for athletes does not appear to be
required.
b. Existing research does not provide enough information to warrant supplementation for
enhanced athletic performance.
J. Choline
1. Functions
a. Required for the formation of the neurotransmitter acetylcholine, which is involved in
muscle activation.
b. It helps maintain the structural integrity of cell membranes.
2. RDA/AI for choline
a. Because of the lack of research on choline, an RDA has not been set.
b. Adequate Intake has been set at 550 and 425 milligrams per day for men and women,
respectively.
3. Complications of choline deficiency
a. Risk is low because it is found in a wide variety of foods.
b. The human body also makes choline endogenously, further decreasing the risk for
deficiency.
4. Symptoms of choline toxicity
a. Signs and symptoms include low blood pressure, diarrhea, and a fishy body odor.
b. Upper limit for choline is 3,500 milligrams per day.
5. Foods rich in choline
a. Lecithin, egg yolks, liver, nuts, milk, wheat germ, cauliflower, and soybeans
b. Choline can be produced in the body from the amino acid methionine.
c. Very few foods have been tested to determine choline levels, thus food value databases
do not contain choline values.
6. Suggestion for a choline-rich meal or snack
a. Roasted Broccoli and Cauliflower recipe (see page 167).
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b. Nutrient databases for choline are incomplete; therefore, a nutrient analysis is not
available.
7. Choline supplements
a. Current research results are equivocal for endurance sports as well as power and
strength sports.
b. More research is needed to clarify choline's role in physical activity and whether
supplementation is beneficial to athletes.
K. Vitamin C (ascorbic acid or ascorbate)
1. Function
a. It is an antioxidant (prevents LDL oxidation, thus reducing the risk for atherosclerosis).
b. Required for the formation of collagen, which is a fibrous protein found in connective
tissues of the body, such as tendons, ligaments, cartilage, bones, and teeth. Collagen
synthesis is also important in wound healing and the formation of scar tissue.
c. It plays a role in a healthy immune system.
d. It enhances iron absorption of nonheme iron, thus protecting the body against irondeficiency anemia.
e. It is required for the formation of various hormones.
f. It is required for the formation of neurotransmitters, such as epinephrine.
2. RDA/AI for vitamin C
a. The RDA is 90 milligrams per day for males and 75 milligrams per day for females.
b. If an individual smokes regularly, which increases oxidative stress and the metabolic
turnover of vitamin C, the RDA increases by 35 milligrams per day.
3. Complications of vitamin C deficiency
a. First signs of vitamin C deficiency are swollen gums and fatigue.
b. If left untreated, the scurvy can develop, causing degeneration of the skin, teeth, and
blood vessels due to low collagen production. The physical manifestations of scurvy
include bleeding gums, impaired wound healing, and weakness.
4. Symptoms of vitamin C toxicity
a. Vitamin C is a water-soluble vitamin, so it is relatively nontoxic.
b. Intakes of greater than 1,500 milligrams a day are not well absorbed, and excesses are
excreted in the urine.
c. Intake levels of greater than the established upper limit of 2,000 milligrams daily may
result in nausea, abdominal cramps, diarrhea, and nose bleeds.
d. Long-term megadoses of vitamin C can also contribute to kidney stones, decreased
absorption of other nutrients, and increased risk for heart disease.
5. Foods rich in vitamin C
a. Citrus fruits and their juices, tomatoes and tomato juice, potatoes, green peppers, green
leafy vegetables, kiwi, and cabbage
b. Refer to Figure 6.9.
6. Suggestion for a meal or snack rich in vitamin C.
a. Snack: Fruit salad made with 1 orange, 2 kiwis, and 3/4 cup cantaloupe
b. Total vitamin C content = 269 milligrams
7. Vitamin C supplements
a. Some research supports the notion that athletes need higher levels of vitamin C than
the RDA due to the oxidative stress of training and competition; other studies show little
or no benefit of vitamin C supplementation on athletic performance.
b. For athletes with adequate vitamin C status, supplementation with vitamin C does not
enhance exercise performance.
c. The U.S. Olympic Committee has approved vitamin C supplements at levels of 250 to
1,000 milligrams per day.
d. Supplements used to achieve higher doses of vitamin C should be consumed with
caution; supplementation can lead to excessive iron absorption and hemochromatosis (in
susceptible individuals).
Author Note: Students should research various sports supplements and vitamin supplements sold in stores and
online. Compare and discuss the levels of water-soluble vitamins present in the supplements, the pros/cons of the
supplements, and suggestions for appropriate use.
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V. What are the fat-soluble vitamins?
A. The fat-soluble vitamins include vitamins A, D, E, and K.
1. They require small amounts of dietary fat to help the body absorb, transport, and utilize them.
2. They can be stored in the body, primarily in fat tissues and the liver, but also in other organ
tissues in smaller amounts.
3. Levels of fat-soluble vitamins in the body can build over time, potentially causing toxicity.
Dietary intake from food rarely causes toxic buildup of the fat-soluble vitamins, but the risk for
accumulating toxic levels in the body increases with the use of supplements containing high levels
of these vitamins.
B. Vitamin A
1. Functions
a. It is found in three different forms—retinol, retinal, and retinoic acid. These three
forms are collectively called retinoids.
b. It plays a role in vision (refer to Figure 6.10).
c. Vitamin A also is involved in cell differentiation.
d. It is essential for tissue repair.
e. It plays a role in immune function by helping to maintain the skin and mucous
membranes (i.e., the epithelial tissues), which act as barriers to infection by bacteria and
other pathogens (sometimes called the "anti-infection" vitamin).
f. It plays a role in bone formation.
g. It helps maintain reproductive health.
h. It shows some promise as an antioxidant in the prevention of cancer and certain
chronic diseases.
2. RDA/AI for vitamin A
a. The RDA for vitamin A for adult males is 900 micrograms RAE and 700 micrograms
RAE for adult females.
b. Standard measurement is the retinol activity equivalent (RAE). One RAE the amount
of a given form of vitamin A is equal to the activity of 1 microgram of retinol (refer to
Figure 6.11).
c. Vitamin A content is often expressed in another measurement, International Units (IU),
which is outdated. Nonetheless, IU is often the way vitamin A is expressed on the labels
of vitamin supplements. When using IU, the recommended intake is 5,000 IU daily.
3. Complications of vitamin A deficiency
a. Vitamin A deficiency is rare in the United States.
b. Blindness is the most common and devastating result of deficiency. Night blindness is
often an early symptom of vitamin A deficiency.
c. Another complication is hyperkeratosis—scaly, bumpy skin.
d. The mucous-producing cells may not secrete mucous, thus causing dryness in the
mucous membranes of the mouth, intestinal tract, female genital tract, male seminal
vesicles, and linings of the eyes. This increases the risk of infection and can cause
infertility in women and sterility in men.
4. Symptoms of vitamin A toxicity
a. Toxicity of vitamin A is rare except in cases of megadoses of vitamin A supplements.
b. Children may be at greater risk of toxicity.
c. Toxicity produces a wide range of symptoms, including skin conditions, vomiting,
fatigue, blurred vision, and liver damage. Vitamin A toxicity can be fatal.
d. Tolerable UL for vitamin A is 3,000 micrograms per day of retinol.
5. Foods rich in vitamin A
a. Good food sources are liver, fish liver oils (e.g., cod liver oil), and egg yolks (refer to
Figure 6.12).
b. Fruits and vegetables that contain high amounts of the carotenoids provide substantial
vitamin A in the diet when converted to retinol equivalents.
c. Dairy products fortified with vitamin A provide additional sources of vitamin A in the
United States.
6. Suggestion for meal or snack rich in a vitamin A
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a. Lunch: Mix 1/2 can of salmon (oil-packed), 1 t lite salad dressing, and chopped onion,
celery, and tomato; serve on 2 slices of whole grain bread with 1/2 cup fresh fruit and 1
cup milk
b. Vitamin A content: 365 micrograms (RAE)
7. Vitamin A supplements
a. Research on supplementing vitamin A in amounts greater than the RDA to improve
sport performance has not shown any ergogenic value.
b. Athletes should be encouraged to obtain vitamin A from food sources rather than
supplements to avoid toxicity.
C. Carotenoids
1. Characteristics
a. Carotenoids are a group of naturally occurring compounds found in plants.
b. They are colorful compounds that give plants and their fruit the deep colors of orange,
red, and yellow.
c. They are not vitamins; however, because some can be converted to vitamin A,
discussion of these compounds has been included in this chapter.
d. Approximately 600 different carotenoids have been identified in plants. The major
carotenoids include alpha- and beta-carotene, lycopene, lutein, zeaxanthin, and
cryptoxanthin.
e. Beta-carotene, alpha-carotene, and beta-cryptoxanthin are provitamin carotenoids.
f. Because they have no vitamin A activity in the body, lycopene, lutein, and zeaxanthin
are called nonprovitamin A carotenoids.
2. Functions
a. They are precursors to vitamin A; therefore, they play a role in vitamin A functions.
b. They have antioxidant properties.
c. They bolster immune function and may play a role in cancer prevention. d. They also
enhance vision.
3. RDA/AI for carotenoids
a. No established RDA/AIs for the carotenoids.
b. Carotenoid consumption was taken into consideration when developing the RAE used
to establish the RDA and UL for vitamin A.
c. Although no DRIs have been established for carotenoids, the Food and Nutrition Board
recommends eating foods rich in carotenoids and avoiding supplementation.
4. Foods rich in carotenoids
a. Deep red, yellow, and orange fruits and vegetables are rich in carotenoids.
b. Tomatoes and tomato products, red peppers, leafy greens, apricots, watermelon,
cantaloupe, pumpkin, squash, sweet potatoes, carrots, and oranges are all excellent
sources of carotenoids.
c. Refer to Fortifying Your Nutrition Knowledge on page 172.
D. Vitamin D, the "sunshine vitamin," can be produced in the body.
1. Functions
a. Vitamin D controls blood calcium levels, which in turn impacts bone growth and
development.
b. Conversion to calcitriol (refer to Figure 6.13).
c. It acts as a hormone. It also may regulate cell differentiation and inhibit cell
proliferation in the blood, lungs, colon, and elsewhere, thus playing a role in cancer
prevention. Further research is needed.
2. RDA/AI for vitamin D
a. AI assumes that no vitamin D is available from synthesis from exposure to sunlight.
b. For men and women aged 19 to 50 years, the AI is 5 micrograms per day.
c. For men and women aged 51 to 70 years, the AI increases to 10 micrograms daily.
d. For men and women older than 70, the AI is 15 micrograms per day.
e. Vitamin D recommendations are often expressed in IU. The IU is presented on food
labels and is used as the unit level for % Daily Values.
f. To convert micrograms to IU and vice versa, the conversion is 1 microgram to 40 IU.
3. Complications of vitamin D deficiency
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a. Lack of vitamin D affects bone growth and development in children (deficiency leads
to rickets, which results in poorly formed, weak, soft bones).
b. In adults, deficiency of vitamin D increases the risk for osteoporosis.
4. Symptoms of vitamin D toxicity
a. Overexposure to the sun or dietary intake of vitamin D from food sources is unlikely to
cause toxicity, but supplementation in high doses can cause problems.
b. UL for vitamin D for adults over age 19 is 50 micrograms, or 2,000 IU.
c. Overdosing with vitamin D causes hypercalcemia, or high blood calcium, which results
in depressed nervous system functioning, muscular weakness, heart arrhythmias, and
calcium deposits in the kidneys, blood vessels, and other soft tissues.
5. Foods rich in vitamin D
a. Fortified forms are included in milk, cereals, and some margarine.
b. Natural sources of vitamin D include fish oils, salmon, sardines, herring, egg yolks,
and liver.
c. Plants are poor sources of vitamin D.
d. Refer to Figure 6.14.
6. Suggestion for a meal or snack rich in vitamin D
a. Bedtime snack: 12 oz skim milk and 2 oatmeal raisin cookies
b. Vitamin D content: 2.45 micrograms (98 IU)
7. Vitamin D supplements
a. In regions of the world where milk is not fortified or where malnutrition, especially in
children, is common, vitamin D supplementation is recommended and needed to prevent
bone formation abnormalities.
b. Perimenopausal and postmenopausal women may benefit from vitamin D and calcium
supplementation to avoid extensive bone loss during menopause.
c. Athletes who consume lower or inadequate amounts of calories, or whose food choices
do not include sources rich in vitamin D on a daily basis, may need supplementation.
d. Athletes who practice and compete mainly indoors may not get adequate sun exposure
to produce the required amounts of vitamin D.
e. A number of strategies can be used to ensure adequate vitamin D levels (refer to page
175).
E. Vitamin E (tocopherols): Only alpha-tocopherol is considered to have vitamin E activity in the body.
1. Functions
a. It has an antioxidant role.
b. It protects the skin and its underlying connective tissues.
c. It protects the cell membranes and genetic material of virtually all tissues of the body.
2. RDA/AI for vitamin E
a. RDA is 15 milligrams of alpha-tocopherol for men and women.
b. The discontinued IU is still found on supplement labels. Refer to conversion formulas
on page 175.
3. Complications of vitamin E deficiency
a. Overt deficiency of vitamin E is rare.
b. Deficiency may occur as a result of malabsorption or maldigestion of lipids, such as
with cystic fibrosis, celiac disease, or hepatic or biliary diseases. The malabsorption of
lipids leads to poor absorption of vitamin E, and thus compromises vitamin E status.
c. Signs and symptoms include muscle weakness, loss of motor coordination, and
hemolytic anemia, causing lack of energy and decreased physical functioning.
4. Symptoms of vitamin E toxicity
a. High doses of vitamin E due to supplementation can affect vitamin K's blood-clotting
functions, leading to excessive bleeding and easy bruising.
b. UL for adults is 1,000 mg of alpha-tocopherol.
5. Foods rich in vitamin E
a. Vitamin E is found in plant oils (and products made from these oils), such as corn,
safflower, cottonseed, sunflower, soy, and palm oils.
b. It is found in some fortified cereals.
c. Refer to Figure 6.15.
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6. Suggestion for a meal or snack rich in vitamin E
a. Nutty Black Bean Salad (see page 176)
b. Total vitamin E content = 27 IU or 18 mg alpha-tocopherol
7. Vitamin E supplements
a. Research has focused on vitamin E's antioxidant effects during exercise.
b. Refer to the section titled, "Which vitamins or compounds have antioxidant
properties?" later in the chapter.
F. Vitamin K
1. Functions
a. It plays a role in blood clotting.
b. It is important for bone health because it assists in the mineralization of bone with
calcium.
2. RDA/AI for vitamin K
a. Due to the lack of data regarding average requirements, no RDA has been established
for vitamin K.
b. The AI for vitamin K is 120 micrograms for men over age 19 and 90 micrograms for
women over age 19.
3. Complications of vitamin K deficiency
a. Impaired blood clotting can lead to substantial hemorrhaging.
b. Individuals more prone to vitamin K deficiency include those with fat malabsorptive
conditions, such as celiac disease, Crohn's disease, and cystic fibrosis, and those taking
long-term antibiotics that may reduce intestinal bacteria.
c. Newborn babies may be at risk for vitamin K deficiency because they lack the
intestinal bacteria at birth that produce vitamin K.
4. Symptoms of vitamin K toxicity—no UL set.
5. Foods rich in vitamin K
a. Best dietary sources of vitamin K are green leafy vegetables, such as spinach and
broccoli.
b. Other foods such as milk, eggs, wheat cereals, and some fruits and vegetables contain
small amounts of vitamin K.
c. Refer to Figure 6.16.
6. Suggestion for a meal or snack rich in vitamin K
a. Green vegetable salad (see page 177)
b. Total vitamin K content = 170 micrograms
7. Vitamin K supplements
a. No known studies that support an increased need for vitamin K in athletes.
b. Supplementation may be indicated for individuals with risks for deficiency or who
present with deficiency symptoms.
c. Supplementation should be provided with physician guidance and supervision; it often
requires a prescription.
Author Note: Students should research various sports supplements and vitamin supplements sold in stores and
online. Compare and discuss the levels of fat-soluble vitamins present in the supplements, the pros/cons of the
supplements, and suggestions for appropriate use.
VI. Which vitamins or compounds have antioxidant properties?
A. Vitamins with antioxidant properties
1. Two fat-soluble vitamins: A (including the carotenoids) and E
2. One water-soluble vitamin: C
B. Free radicals
1. Highly reactive molecules, usually containing oxygen, that possess unpaired electrons in their
structure (refer to Figure 6.17).
a. Unpaired electrons give free radicals an ionic charge, which makes them reactive with
other charged molecules in the body.
b. Free radicals basically cause molecules to give up electrons in a process know as
oxidation so that they can match any unpaired electrons and become more stable.
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c. Undesirable free-radical oxidation may damage DNA, lipids, proteins, and other
molecules, and thus may be involved in the development of cancer, cardiovascular
disease, and possibly degenerative nerve diseases.
2. Formation of free radicals
a. They are produced in the body as byproducts of normal cellular metabolism (formation
of reactive oxidative species).
b. Outside sources of free radicals include the breathing of polluted air, such as when
runners exercise in congested traffic.
3. Combating free radical damage
a. The body produces a variety of antioxidant enzymes capable of catalyzing reactions
that neutralize free radicals.
b. Healthy dietary practices supply the body with antioxidant vitamins, such as vitamins
A (including the carotenoids), E, and C. These nonenzymatic antioxidants either directly
interact with free radicals (refer to Figure 6.18) or work as coenzymes.
c. Example: Lipid peroxidation (see pages 178–179 and Figure 6.17)
C. Relationship between free radicals and exercise
1. Free radical production has been shown to increase during exercise, particularly during
sustained high-intensity aerobic exercise.
a. The reason for this is not well understood, but it is believed to be related to the
increased presence and utilization of oxygen by the mitochondria within the muscle cells
to make ATP.
b. The free radicals that are produced are usually neutralized by an elaborate antioxidant
defense system of enzymatic and nonenzymatic antioxidants.
2. It appears that the body's own natural antioxidant defense system is adaptable and up-regulates
its response to extended training, protecting muscles and other tissues from damage during future
exercise bouts.
D. Antioxidant supplements
1. Although the use of antioxidant supplements appears promising, there are still no governing
bodies that recommend regular intake of antioxidants at levels higher than the RDA/AIs.
2. Unfortunately, research into the effects of taking nonenzymatic antioxidant supplements (i.e.,
vitamins A, C, and E) on free radical levels during exercise is presently unclear.
3. At present, recommendations to well-nourished athletes regarding antioxidant supplementation
is neither necessary nor advisable.
VII. What are phytochemicals?
A. Characteristics
1. Although they are not nutrients, they have important health functions.
2. They are chemical substances found in plants. It is estimated that there are thousands of these
plant chemicals, and they may significantly affect the human body.
3. Research on the many benefits of phytochemicals to human health varies for different classes
and specific compounds.
4. Further research is needed to determine what role specific phytochemicals play in reducing
chronic diseases. The effects of phytochemicals on exercise and sport performance are not well
researched.
5. Although research has focused on health and disease prevention, and not on sport performance,
athletes can reap the benefits of good health by consuming a phytochemical-rich diet.
6. Refer to Table 6.2 for a summary of a variety of phytochemicals and examples of good food
sources of these phytochemicals.
B. Phenolic compounds
1. Phenols are a large and varied group of phytochemicals found in many different foods.
2. The majority of the research on phenols is related to their influence on heart disease prevention
(e.g., prevention of LDL oxidation).
3. Phenols are found in grapes and red wine.
a. The presence of flavonoids in wine and grapes started a debate about the benefits of
wine consumption in combating heart disease (i.e., the "French paradox").
b. Grape seeds and skins are considered good sources of polyphenolic tannins; the
phenolic compounds catechin and anthocyanin are also abundant in grapes.
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c. New evidence suggests that nonalcoholic wine and commercial grape juice can provide
similar amounts of flavonoids and antioxidant capacity as red wine.
d. Because alcohol consumption is generally not recommended as part of an athlete's diet,
sparkling grape juice can provide a healthy nonalcoholic alternative.
4. Teas
a. Teas contain flavonols and polyphenols, most significantly catechins.
b. Green and black teas both contain these phytochemicals; however, green tea has been
found to have higher concentration of polyphenols.
c. Regardless of the type of tea, the antioxidants may act in cancer prevention and
cardiovascular disease protection.
d. Consuming several cups of green or black tea daily will help athletes reap the potential
disease prevention benefits of this beverage.
C. Organosulfides
1. The cruciferous vegetables contain a variety of organosulfide compounds, including
glucosinolates, indoles, and isothiocyanates, and have long been touted for their anticancer
properties.
2. Many vegetables, including broccoli, brussels sprouts, cabbage, rutabaga, and cauliflower, have
organosulfide phytochemicals.
3. Garlic, onions, leeks, chives, and shallots contain allyl compounds, which provide flavor and
odor to foods.
a. These foods offer many possible health benefits, including reducing blood cholesterol
levels and cancer risk, and they may have antihypertensive potential.
b. These foods may also protect against cancers of the gastrointestinal tract.
4. Athletes should include cruciferous vegetables, garlic, onions, and other pungent vegetables in
their daily diet to gain the potential health benefits.
a. These high gas-producing vegetables should be avoided within several hours before
training.
b. Best practice is to consume these vegetables after workouts or competitions to avoid
uncomfortable gas production but reap the health benefits.
D. Lycopene
1. Lycopene is one of the most well-studied carotenoids and is widely recognized by the public.
2. There is a strong correlation between lycopene intake and prostate health.
3. Tomatoes and tomato products, such as ketchup, tomato pastes and sauces, canned tomatoes,
and tomato-based products, such as enchilada sauce, pizza sauce, picante sauce, and salsa, are
good sources of lycopene.
4. Fresh tomatoes appear to have less bioavailable lycopene than processed tomatoes, because
cooking releases the lycopene stored in the cell walls of fresh tomatoes.
5. Absorption of lycopene is greater with the simultaneous intake of fat.
6. Some research suggests that lycopene is beneficial in a variety of ways for active individuals.
a. It may protect against exercise-induced asthma.
b. It may reduce oxidative stress.
c. It may offer protection from ultraviolet sunlight.
d. However, many of these studies contained small sample groups, combined other
antioxidant supplements with lycopene, and were conducted primarily in animals, not
humans. Further research is needed before any definitive answers about lycopene's effects
in these areas can be drawn.
E. Phytochemical consumption can be increased by eating whole foods.
1. Focus on a plant-based diet.
2. Refer to Training Tables 6.1 through 6.3.
3. Refer to pages 182–183 for tips on how athletes can consume more plant-based foods, thus
increasing phytochemical intake.
4. Athletes should be encouraged to eat a wide variety of fruits and vegetables to help ensure
adequate intake of phytochemicals.
5. Because DRIs have not been established for phytochemicals, the need for supplementation by
athletes is currently unknown.
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