Water soluble - B1 (thiamin), B2 (riboflavin), B3(niacin), B6(pyridoxime), B12 (cyanocobalamin), C (ascorbic acid), Panthothenic Acid, Biotin, Folic Acid
Care should be taken if one relies on diet to supply all of the body's vitamin requirements. With current food processing, cooking, harvesting, weather and genetics there is wide variability of vitamins in foodstuffs.
Chemical Structure of Vitamins
Vitamin have complex organic chemical structures. Some vitamins are also mixtures of compounds.
RDA - Recommended Daily Allowance
Federal Health Organizations such as Health Canada and the Food and Drug Administration of the U.S. have given RDA (Recommended Dietary Allowance) values for food constituents and vitamins. A number of units are use to measure daily allowances including IU (International Units) which are a measure of biological activity and equivalent to a certain mass of the specific vitamin. For vitamins that have groups of compounds whose biological activity differ other units are used. For example vitamin A doses are measured in retinol equivalents which are equal to 1 microgram of retinol. The substitute for retinol beta-carotene is less effective and need 6 micrograms to equal one retinol equivalent. The recommendation is usually modified for age and gender and sometimes pregnancy.
Vitamin A
Vitamin A (retinol) is necessary for the synthesis of the pigments such as rhodopsin which used in the retina of the eye and used in vision. Vitamin A is also involved in mucus membranes, bone growth, reproduction and immune functions.
Sources: Vitamin A only occurs naturally in animal materials - meat, milk, egg yolks. Plants contain only the precursor to the vitamin, beta-carotene. Humans and animals can readily convert beta-carotene to vitamin A in the liver. Provitamin A (carotene) is found in green leafy vegetables, carrots and spinach.
Health Issues: Vitamin A deficiency leads to blindness, a failure of normal bone development in the young and diseases of the membranes on the nose, throat and eyes. Vitamin A deficiency is very common in the developing world. Taking excesssive amounts of vitamin A can be harmfull; causing nausea, skin damage, bleeding of the mucosa and even death.
RDA: 1000 "Retinol Units" (1mg) per day is recommended for an adult male. 80% of this for a female.
Vitamin D
The primary purpose of vitamin D is to increase the absorption of Ca and P from the gut so that these elements can be used to make bone.
Sources: The vitamin can be formed in the skin by activation of sterols (ergosterol and cholesterol) in the presence of sunlight. Natural exposure to sunlight will normally provide adequate levels of vitamin D. Most foods are low in this vitamin. Good sources are liver, fish oils (cod liver oil), dairy products and eggs. Our packaged milk is now fortified with A and D vitamins.
Health Issues: Vitamin D deficiency primarily results in the bone disease rickets in children and osteomalacia in adults.
RDA: 2.5 micro grams of cholecalciferol per day. For children an intake of 10 micro grams - equivalent 400IU (International Units) per day is recommended. Milk is fortified with approximately this amount per litre. Taking excessive amounts of vitamin D can destroy renal tissue and cause skeletal deformities. Muscular spasms and physological disturbances are also symptoms of excessive vitamin D intake.
Vitamin E
Vitamin E activity in food is from a series of compounds called the tocopherols and tocotrienols (trienols). Eight forms are found in nature. The vitamin is an anti-sterility factor in rats and is required for normal muscle tone in animals but its role in humans is largely unknown.
Vitamin E is a natural antioxidant that helps prevent cellular damage - stabilizes cell membranes. It is thought to reduce the risk of some forms of cancer and heart disease. High intake of polyunsaturated fatty acids may produce high concentrations of peroxidized fatty acids that could be harmful. Vitamin E can reduce or prevent this process from occuring. Vitamin E also helps in iron absorption and prevent vitamin A and carotene from being damaged by oxidation.
Sources: Vitamin E can be found in most vegetable oils, cereals and liver.
Health Issues: A deficiency of vitamin E is rare. Low birth weights and anemia have sometimes been related to vitamin E deficiency. High doses of Vitamin (400-800 IU per day) E have been promoted as decreasing the risk of certain forms of cancer and heart disease. Claims of anti-aging properties and increasing sexual potency are unsubstantiated.
Sources: Good sources of vitamin E are vegetable oils, cereal products, liver and vitamin supplements
RDA: For children 3-5mg per day. Adults - 9 mg for males 6 mg for females.
Vitamin K
Vitamin K is essential for the normal blood clotting process.
Sources: Green leafy vegetables such as spinach and cabbage, liver, soybeans and supplements are good sources of vitamin K. The vitamin is also synthesized in the human intestinal tract by certain bacteria.
Health Issues: A deficiency of vitamin K can result in defective blood clotting in children and adults. A deficiency can be brought on by long-term antibiotic therapy which destroys gut bacteria, halting the synthesis of vitamin K.
Vitamin B1
Vitamin B1 (thiamin) was one of the first vitamins found. As with many of the B vitamins, thiamin is involved in releasing energy from carbohydrate, alcohol and fat. The effective use of carbohydrates is dependent on this vitamin which functions as the coenzyme thiamin pyrophosphate, or cocarboxylase, in the oxidation of glucose.
Hydrochloric acid (stomach acid) is necessary for thiamin absorption.
Foods preserved with sulphur dioxide and sulphite can destroy thiamin and should not be used if this food is considered a thiamin source.
Sources: Good sources of thiamin include wheat germ, whole grains and pork, yeast and egg yolk.
Health Issues: Thiamin is an anti-neuritic factor. Deficiency results in general nervous atrophy -- the disease Beriberi. Symptoms include weakness, loss of appetite and numerous nervous disorders. Additional thiamin deficiency symptoms include edema, an enlarged heart and tachycardia.
RDA: 1.0-1.5 mg per day depending on age and gender.
Vitamin B2
Vitamin B2 (riboflavin) is a component of several enzymes necessary for carbohydrate, fat and protein metabolism.
Riboflavin is important for flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). These compounds help regulate cellular metabolism through oxidation-reduction reactions.
Sources: Riboflavin is the yellow-green pigment of skim milk and whey. Other sources are meats, nonfat milk and oysters. The vitamin is very sensitive to destruction by light. To protect the vitamin, milk is better distributed to the consumer in packages rather than clear bottles.
Health Issues: A deficiency of riboflavin can result in decreased growth, nervous disorders, degeneration of nerve myelin sheaths, edema and photophobia.
RDA: 1.2-1.7 mg per day depending on age and gender.
Vitamin B3
Vitamin B3(niacin) is involved tissue respiration; also glucose, fat and protein oxidation - over 40 biochemical reactions in all. This vitamin is also referred to as nicotinamide or nicotinic acid (nothing to do with tobacco).
Niacin is important for normal tissue integrity, especially the skin, gastrointestinal tract and the nervous system.
Sources: Niacin is found in a wide variety of foods. Good sources are yeast, meats, seafood, poultry, peanuts, mushrooms,legumes, whole grain cereals, and green vegetables. Niacin may also be added to enriched breads and cereals to help replace niacin loss during processing.
Health Issues: A deficiency of niacin can result in the disease Pellagra. This is characterized by diarrhea, loss of appetite, skin and mucous membrane disorders, decreased growth, nervous disorders.
RDA: 13-20 mg per day depending on age and gender.
Vitamin B6
Vitamin B6 consists of several compounds including, pyridoxal, pyridoxamine and pyridoxine. It is essential for protein metabolism, and for the formation of haemoglobin - the pigment in the blood that carries oxygen round the body.
Sources: Good sources of vitamin B6 are muscle meats, green vegetables, cereal grains, bran and bananas.
Health Issues: A vitamin B6 deficiency does not produce an easily recognized disease. Symptoms can include dermatitis, convulsions, anemia and excitability.
RDA: 2.0 mg per day for adults 2.2 mg during pregnancy.
Pantothenic Acid
Pantothenic acid is considered a member of the B group of vitamins. It is important for normal tissue metabolism and is involved with the synthesis of fatty acids, cholesterol and sterols. It is found in two enzymes - coenzyme A and acyl-carrier-protein (ACP).
Sources: Pantothenic acid is found in a wide variety of plant and animal foods, including in yeast, and eggs.
Health Issues: Deficiencies are rare. Symptoms include, fatigue, less resistance to stress, lack of well being.
RDA: Not well established; thought to be about 5mg per day.
Vitamin B12
Vitamin B12 (cyanacobalamin) is a group of compounds essential for several enzyme systems involving the transfer of one-carbon units for the methylation of homocysteine. Vitamin B12 is also important in the metabolism of nucleic acids and proteins.
Sources:Vitamin B12 is found in meats, liver, fish, poultry and milk.
Health Issues: Vitamin B12 deficiency can result in anemia, fatty liver, and peripheral nerve degeneration. Many older people suffer from pernicious anemia that can be alleviated with regular injections of this vitamin.
RDA: 3 mg per day.
Biotin
Biotin is involved in the metabolism of fatty acids and amino acids - essential for carbohydrate, fat and protein metabolism. It is involved in the conversion of protein and carbohydrate into fat. When the level of carbohydrates in the body is low, biotin helps maintain normal blood glucose levels from fat and protein sources.
Sources: the diet is seldom short of biotin. Good sources include, milk, eggs, liver and yeast.
Health Issues: Biotin deficiencies are rare but can result in anorexia, nausea and depression. Large intakes of raw egg whites (containing avidin) may induce a deficiency.
Folic Acid
Folic (folacin) is a component of tetrahydrofolic acid, which is involved in the transfer of one-carbon groups - i.e. the transfer of methyl groups to help resynthesize methionine from homocysteine and to form choline. Folic acid is also important in the synthesis of purines and pyrimidines.
Sources: Good sources of folic acid include liver,leafy vegetables (spinach) legumes, nuts and cereal grains
Health Issues:Folic acid deficiency can cause megaloblastic anemia (defective DNA synthesis resulting in abnormal red blood cells (especially in bone marrow), diarrhea,fatigue and depression. A sufficient intake of folic acid is especially important during pregnancy for normal cell development of the foetus.
RDA: 200 micro grams per day for males 180 micrograms for females (400 micro grams during pregnancy)
Vitamin C
Vitamin C (Ascorbic Acid) is an antioxidant and is involved in the synthesis of protein collagen which is necessary for skin and connective tissue. This vitamin, like vitamin E aids in the absorption of iron. Man is one of only a few mammals unable to manufacture ascorbic acid in his liver.
Sources: Vitamin C is easily destroyed by food processing (oxidation) especially heat. Good sources of vitamin C are citrus fruits, papaya, green peppers, broccoli, brussels sprouts, cauliflower, cabbage. Potatoes also contain small amounts of vitamin C. Animal products, milk and cereals are poor sources.
Health Issues:A deficiency of vitamin C can result in the disease scurvy - a common illness among mariners who did not have a source of fresh fruits and vegetables. Symptoms include fatigue, loss of appetite, retarded wound healing and fragile capillaries (bleeding gums). Loose teeth and bone joint diseases are also common.
High daily intake of vitamin C (1000mg or more) has been recommended to lower blood cholesterol and prevent colds. These claims have yet to be proven.
RDA: Not an international agreement - 60 mg per day for male and female in the US; 30 mg per day in Canada and UK.
Choline
Choline is generally listed as a vitamin. It is considered as essential, mainly for infants and is involved in lipid transport, cell membrane structures and brain tissue. It functions in the transmission of nerve impulses (acetyl choline). It is thought that adults can synthesize sufficient amounts of choline (possibly by intestinal bacteria) so it is not a vitamin in a strict sense.
Sources: Good sources of choline are lecithin, seed oils, liver and egg yolks.
Health Issues:Choline has been used to treat Alzeimer's disease and fatty liver.
