A. Alice H. Lichtenstein, DSc, executive editor of the Tufts Health & Nutrition Letter, answers: “Biotin is a water-soluble vitamin also called vitamin B7. It is essential to certain steps in metabolism and is a key regulator of gene expression. Adequate intake of biotin for people over age 19 is 0.3 milligrams (mg) a day. Since it is estimated that most U.S. adults get 0.4 to 0.6 mg a day from foods, biotin deficiency is rare in healthy individuals. Egg yolks are a major source of biotin, with about 0.25 mg in just one large egg. Biotin is also found in smaller amounts throughout the food supply.
“There is only limited evidence of biotin’s affect on the skin, hair, and nail disorders it is marketed to treat. The U.S. Food and Drug Administration has issued a warning that high supplemental doses of biotin can cause false negatives on diagnostic tests, including an important test for heart attacks. Talk to your doctor if you are currently taking biotin or are considering adding biotin, or a supplement containing biotin, to your diet.”