Biotin

Description

Biotin is one of the vitamin B-Complex vitamins. It is a cofactor for many enzymatic reactions occurring in mammalian cells. Biotin is needed for growth, maintenance of skin, nerves, sex glands, bone marrow, and sebaceous glands.

Until recently, biotin was not recognized as being clinically significant because it was believed that the gastrointestinal bacteria produced a sufficient amount of biotin for the body's needs. In the early 1970's however, an inborn error of biotin metabolism was reported and, shortly thereafter, other biotin deficient individuals were recognized.

Biotin is stable when food is heated, stored, or processed.

Method of Action

Biotin is involved with the metabolism of fatty acids, amino acids, and carbohydrates. It is used as a coenzyme for the removal of carbon dioxide from oxaloacetate, succinate, malate, and aspartate; it is also used in the biosynthesis of citrulline, aspartate, and unsaturated fatty acids, and in other reactions involving the transfer of carbon dioxide.

Biotin in enzymes is usually connected to a lysine residue. There are nine known enzymes which require biotin to function, but only four of the nine exist in mammalian cells; the other enzymes are found in microorganisms.

Properties & Uses

Biotin has been used successfully to treat seborrheic dermatitis in infants in the United States and Europe. Inconclusive results have been achieved in the treatment of other skin and scalp disorders, such as baldness.

Consequence of Deficiency

Biotin deficiencies are not frequently found in humans. The small amount of biotin required is usually supplied by the diet and by microorganisms in the gastrointestinal tract.

One possible cause of biotin deficiency is the eating of raw egg white. Raw egg white contains avidin which complexes to biotin and prevents its absorption into the body. Other causes of biotin deficiency include other antagonists to biotin as well as inborn metabolic errors.

The symptoms of biotin deficiency are: dermatitis, nausea, depression, vomiting, and anorexia. These symptoms occur only under highly abnormal, or experimental, conditions.

Toxicity Factors

Biotin is essentially nontoxic to humans.

Recommended Dietary Allowance

RDA for adults:	150 - 300 mcg
RDA for children:	Unknown

The above is 1980 values for RDA.

Biotin is taken orally for biotin deficiency.

For over thirty years, Recommended Daily Amounts has existed in the United Kingdom. It has been used to measure the adequacy of an individual's diet. However, in 1991 the Committee on Medical Aspects of Food Policy (COMA) gave forth a whole new set of figures upon the request of the Department of Health's Chief Medical Officer. Reference Nutrient Intake (RNI) is one of these sets collectively known as "Dietary Reference Values." RNI is an amount of a nutrient that is enough for almost every individuals, even someone who has high needs for the nutrient. This level of intake is, therefore, considerably higher than what most people would need. If individuals are consuming the RNI of a nutrient they are most unlikely to be deficient in that nutrient.

The United Kingdom RNI in the COMA 1991 repor suggests that intakes between 10 and 200mcg are both safe and adequate.

Food Sources

High

Lamb liver	Pork liver
Royal jelly	Yeast

Medium

Almonds	Barley
Beef liver	Cauliflower
Chicken	Chocolate
Corn	Cowpeas
Eggs	Garbanzos
Hazelnuts	Lentils
Mackerel	Mushrooms
Oat flakes	Peanuts
Pecans	Rice
Salmon	Sardines
Soybeans	Walnuts
Wheat

Low

Apples	Avocados
Bananas	Cantaloupe
Cheese	Grapefruit
Grapes	Milk
Oranges	Peaches
Strawberries	Watermelon

References

Appel J.J., Briggs G. M., In Goodhart R.S., Shils M.E., eds: Modern Nutrition in health and disease (6th ed). Philadelphia: Lea & Febiger, p 274, 1980.

Bonjour, J.P. ; Int. J. Vit Nutr. Res 47:107, 1977.

Cowan, M. 1984. Biotin responsive metabolic disorders in early childhood. In Recent Vitamin Research. M.H. Briggs. Crc Press, Inc. Boca Raton, FL

Goodhart, Robert S. & Maurice E. Shills. Modern Nutrition In Health And Disease. 6th edition. Philadelphia: Lea and Febiger, 1973.

Griffin, H Winter M.D. Complete guide to Vitamins minerals and supplements. Fisher Books, Tuscon Az p. 32, 1988.

Hegsted, M.D. 1976. Present Knowledge In Nutrition. 4th ed. The Nutrition Foundation Pub., Washington D.C. 605.

Howe, P.S. 1981. Basic Nutrition in Health and Disease, 7th ed. W.B. Saunders Co., Philadelphia.

Kirschmann, J.D. Nutrition Almanac: Nutrition Search. McGrew-Hill: New York. 1990.

Koutsikos-D et al: Glucose metabolism in normoglucaemic haemodialysis patients: a possible role for biotin? [letter] Nephrol-Dial-Transplant. 1995; 10(7): 1256-7.

Kutsky, R.J. 1973. Handbook of Vitamins and Hormones. Van Nostrand Reinhold, Co. New York, New York. 278.

McClain, C.J., Baker, H., Onstad, G. R.; J.A.M.A. 247:3116, 1982.

Mock, D.M., Boswell, D.C., Baker, H., et. al.; J. Pediatr. 106:762, 1985.

Murray, M.T. & Pizzorno, J.E. Encyclopedia of Natural Medicine. Rocklin, CA: Prima Publishing,1991.

Velazquez-A et al: Biotin supplementation affects lymphocyte carboxylases and plasma biotin in severe protein-energy malnutrition. Am-J-Clin-Nutr. 1995 Feb; 61(2): 385-91.

Walji, H., Vitamin Guide: Essential nutrients for healthy living., Element: Dorset, U.K. 1992.

Walji, H., Vitamin Minerals & Dietary Supplements., Hodder Headline Plc.: London, U.K. 1994.

Whitney, E.N. & C.B. Cataldo. 1983. Understanding Normal and Clinical Nutrition. West Publishing Company. St. Paul, Min. 1230.