Biotin

Biotin, also known as vitamin B7, is a water-soluble B vitamin that acts as a cofactor for carboxylase enzymes involved in the metabolism of fats, carbohydrates, and amino acids. It is naturally present in a variety of foods and is also produced by gut bacteria.

As a coenzyme, biotin is required by several carboxylases, including acetyl-CoA carboxylase, pyruvate carboxylase, and propionyl-CoA carboxylase. These enzymes participate in fatty acid synthesis, gluconeogenesis, and the catabolism of certain amino acids, making biotin essential for energy production and metabolic balance.

Dietary sources of biotin include egg yolks, liver, nuts and seeds, dairy products, and some vegetables. The general adult adequate intake is about 30 micrograms per day, and most people obtain sufficient biotin from a varied diet. Biotin is also widely added to some fortified foods and supplements.

Biotin deficiency is rare in developed countries but can occur with prolonged raw egg white consumption (which contains avidin that binds biotin), malabsorption syndromes, certain genetic disorders such as biotinidase deficiency, or prolonged use of specific medications. Deficiency can cause dermatitis, alopecia, conjunctivitis, and, in severe cases, neurological symptoms.

Biotin supplements are popular for hair, skin, and nails, though robust evidence for cosmetic benefits is limited. High-dose biotin is generally well tolerated, but very large intakes can interfere with laboratory tests and lead to falsely high or low results, potentially complicating diagnosis and treatment.