To Your Health

Q. Until recently I had never heard of a vitamin called biotin. What is it good for, and what foods have it?

A. Biotin is a water-soluble B vitamin every bit as important to health as other vitamins. It gets very little attention, however, because severe deficiency is rare in people who eat a normal diet. The extremely low incidence of biotin deficiency is probably due to a combination of factors. First, our intestinal bacteria synthesize biotin, and we can absorb at least some of that. Second, the daily requirement is low, and biotin is found in almost all foods. As with other B vitamins, look first to liver for a food source of biotin, although eggs have almost as much and other whole foods have reasonable amounts.

The most common symptoms of biotin deficiency, and the first to be noticed, are skin and hair problems. Because of this observation it was originally called vitamin H (from haut, the German word for skin), but if the deficiency persists symptoms can worsen and progress to depression, lethargy, hallucination, and numbness of the extremities.

Recent research indicates that during the course of pregnancy, biotin reserves usually decrease. Though it was not severe enough to cause skin or hair symptoms, approximately half of pregnant women had laboratory evidence of biotin deficiency. There is still reason for concern because even mild biotin deficiency in several animal species has been shown to cause birth defects. Along with the more well-known need to supplement with folic acid during pregnancy, it would be easy to add a supplement of biotin.

Although biotin deficiency is rare, it can happen. Consumption of several raw eggs each day for many weeks or years has produced biotin deficiency. The problem is actually the uncooked egg white, which contains a protein known as avidin. Avidin irreversibly binds to biotin and prevents its utilization as a vitamin. Heating the egg whites, a process that inactivates avidin, easily prevents the problem. This feature tends to put a natural limit on the consumption of eggs, apparently helping assure the survival of avian life.

Since we depend on the bacteria that normally inhabit the large intestine to produce a meaningful portion of the biotin we need, prolonged use of oral antibiotics has been associated with biotin deficiency. If it is necessary to use antibiotics for more than a few weeks, a biotin supplement of 300 micrograms per day is generally recommended. Because the antibiotic will kill the normal intestinal bacteria, as soon as the antibiotic is discontinued use an acidophilus supplement for a few weeks to re-establish the colony.

Japanese researchers studied people with type 2 diabetes and found that they had significantly lower biotin levels than people who didn't have the disease. The researchers then gave the diabetics a biotin supplement of 9,000 to 16,000 micrograms daily and found that their blood-sugar levels were cut nearly in half. With the incidence of type 2 diabetes in America on the rise, biotin could become a hot item in the future.

Although you probably get enough biotin in your diet, it is one of the safest of all vitamins to supplement. There are no reports of toxicity, even when it's taken in doses far above the amounts found in food.