The B-complex includes eight different water-soluble vitamins that perform various physiological duties, among which is helping you metabolize food into energy. Because they are water-soluble, your body is unable to store B-complex vitamins, and you must eat foods containing these compounds on a daily basis to meet your needs. Vitamin B-7, or biotin, is one of the B vitamins.
The primary function of vitamin B-7 is to act as a coenzyme for reactions that involve the addition or removal of carbon dioxide to or from biologically active compounds. For example, the synthesis and oxidation of fatty acids requires vitamin B-7 to act as a coenzyme. It also helps to break down proteins into amino acids and plays a role in the formation of purines.
Adults over the age of 18 and pregnant women need 30 mcg of vitamin B-7 a day to adequately meet the body's needs. Lactating women need 35 mcg a day.
Vitamin B-7 deficiency can occur under certain circumstances. Biotin-dependent multiple carboxylase deficiency syndrome is an inherited disorder causing biotin deficiency. People reliant on total parenteral nutrition -- intravenous nutrition -- can also become biotin deficient. You can also become deficient if you eat too many raw egg whites. A substance in egg whites called avidin binds with vitamin B-7 in the intestines, preventing you from absorbing it. Smokers also may be at risk for vitamin B-7 deficiency. Symptoms of vitamin B-7 deficiency include dry and scaly dermatitis, nausea, vomiting, anorexia and alopecia. Depression, listlessness, hallucinations and tingling in the arms and legs can also occur.
Good Food Sources of Vitamin B-7
Vitamin B-7 is found in a number of natural foods. Good food sources include organ meats, egg yolks, soybeans and yeast. A 100-g serving of chicken liver contains the highest amount of vitamin B-7 with 170 to 200 mcg. A 100-g serving of brewer's yeast contains 200 mcg. A 100-g serving of raw egg yolk contains 60 mcg.
Moderate Sources of Vitamin B-7
Foods with moderate amounts of vitamin B-7 include fish, nuts and oatmeal. A 100-g serving of fish contains 3 to 24 mcg. Walnuts and peanuts contain the highest amount, with 39 and 34 mcg per 100-g serving, respectively. A 100-g serving of oatmeal contains 22 to 31 mcg.
As a water-soluble vitamin, vitamin B-7 toxicity is unlikely to occur and there are no known toxic effects, according to the authors of "Krause's Food, Nutrition and Diet Therapy."