HLTH 213
Vitamin Lecture
Vitamins
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.
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 fat-soluble 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.
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, B6, 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.
C. Riboflavin (vitamin B2)
1. Functions
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.
5. Foods rich in niacin
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
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 B6 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 B6
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 B6 metabolism during short- and long-duration exercise to establish recommendations for supplementation during training or competition.
F. Vitamin B12 (cobalamin)
1. Functions
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 B12. 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 B12 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 B12
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 B12 from fortified vegetarian foods, soy products, or multivitamins.
b. Masters or elderly athletes may also need B12 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 B12 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
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 folatedeficiency
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 B12 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 toBlack-Eyed Peas with Chinese Greensrecipe on page 165.
b. Refer to Figure 6.7.
7. Folate supplements
a. A multivitamin can be used to ensure adequate intake.
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 cholinedeficiency
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).
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 iron-deficiency 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 Cdeficiency
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.
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.