biotins

Biotin, also called vitamin B7, is a water-soluble B-complex vitamin that functions as a coenzyme for carboxylase enzymes, enabling key steps in fatty acid synthesis, gluconeogenesis, and amino acid metabolism. The active coenzyme form is biotin attached to carboxylases as biotinylated lysine; humans obtain biotin from the diet and from gut microbiota, which synthesize small amounts.

Dietary sources include organ meats, eggs, fish, meat, dairy products, nuts, seeds, legumes, and some vegetables. Raw egg whites contain avidin, a protein that binds biotin and reduces its absorption; cooking inactivates avidin.

Biotin deficiency is uncommon in developed countries but can occur with prolonged malnutrition or malabsorption, and in rare genetic disorders such as biotinidase deficiency and holocarboxylase synthetase deficiency. Symptoms include thinning hair, dermatitis, glossitis, depression, and, in infants, seizures. Certain medications and conditions that impair absorption can also contribute.

Recommended intake for adults is about 30 micrograms per day. There is no established upper intake level due to low toxicity, though very high-dose supplements marketed for hair and nail health may interfere with some laboratory tests. Evidence for routine cosmetic benefits in people without deficiency is limited.

In practice, biotin supplementation effectively corrects deficiency and is generally safe at typical doses. It is not a proven preventive measure for hair loss or other cosmetic concerns in individuals with normal biotin status.