Recommended dietary allowance biotin

Vitamins are chemically unrelated organic compounds that cannot be synthesized by humans and, therefore, must must be supplied by the diet. Nine vitamins (folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid) are classified as water-soluble, whereas four vitamins (vitamins A, D, K, and E) are termed fat-soluble (Figure 28.1). Vitamins are required to perform specific cellular functions, for example, many of the water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism. In contrast to the water-soluble vitamins, only one fat soluble vitamin (vitamin K) has a coenzyme function. These vitamins are released, absorbed, and transported with the fat of the diet. They are not readily excreted in the urine, and significant quantities are stored in Die liver and adipose tissue. In fact, consumption of vitamins A and D in exoess of the recommended dietary allowances can lead to accumulation of toxic quantities of these compounds. 

There is no recommended dietary allowance for biotin, although it suggested that a safe and adequate oral intake is 85 pg for four- to six-year-olds and 100-200 pg for adults (Recommended Dietary Allowance, 1980). A recent review contains a recommendation of 30 pg/kg/d for infants and 5 pg/kg/d for adults fed intravenously (Shenkin and Wret-lind, 1978). 

National Research Council, Food and Nutrition Board, and Institute of Medicine (1998) Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B-6, folate, vitamin B-12, pantothenic add, biotin, and choline. In Recommended Dietary Allowances., pp. 374-389. Washington, DC. National Academy Press. 

The body s need for most vitamins is relatively low. The amounts needed to ensure the normal physiological function of humans is dependent on many factors such as age, sex, health status, lifestyle, eating habits and work-related activity. Many countries have recommendations for the daily intake of vitamins, which are continually revised in accordance with contemporary scientihc knowledge and dietary guidelines. Presently, Recommended Daily Allowances (RDAs) are set in the EU (upper number) and United States (lower number) as follows vitamin A (800/900 xg), vitamin D (5/15 xg), vitamin E (12/15 mg), vitamin K (75/120 xg), thiamine (1.1/1.2 mg), riboflavin (1.4/1.3 mg), niacin (16/16 mg), pantothenic acid (6/5 mg), vitamin Bg (1.4/1.3 mg), biotin (50/30 xg), folacin (200/400 (xg), vitamin Bj2 (2.5/2.4 xg) and vitamin C (80/90 mg). 

RDA have been established for many essential nutrients however, present knowledge of human nutritional needs of pantothenic acid and biotin is incomplete. Therefore, to ensure adequate nutrient intake, obtain the recommended allowances from as varied a selection of foods as possible. Nutritionists suggest that dietary planning include regular intake of each of the four basic food groups ... 

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