Vitamin B7 (Biotin)

Biotin, also known as vitamin B7 or vitamin H, functions as a covalently bound coenzyme for five carboxylase enzymes in humans: acetyl-CoA carboxylase (fatty acid synthesis), pyruvate carboxylase (gluconeogenesis), propionyl-CoA carboxylase (amino acid and odd-chain fatty acid metabolism), and two forms of methylcrotonyl-CoA carboxylase (leucine catabolism). These reactions are fundamental to intermediary metabolism. Biotin also plays a role in gene regulation through histone biotinylation. While biotin is heavily marketed for hair and nail growth, robust evidence for benefits in non-deficient individuals is limited. Deficiency is rare but can occur during pregnancy, with prolonged antibiotic use (which reduces gut bacterial biotin synthesis), and with high raw egg white consumption (avidin in raw egg whites binds biotin). Importantly, biotin supplementation can interfere with immunoassay-based laboratory tests, producing falsely elevated or decreased results for thyroid hormones, troponin, and other analytes.