Biotin (Vitamin B7)

Key points

• Biotin is a cofactor for carboxylase enzymes — involved in fatty acid synthesis, amino acid metabolism, and gluconeogenesis
• Deficiency causes hair thinning and brittle nails — supplementation reverses this in deficient individuals
• Most people get adequate biotin from food; supplementation is most useful when combined with B12 for hair and nail support
• 5000mcg (5mg) is the typical supplement dose — far above RDA but excess is excreted harmlessly in urine
• Raw egg whites contain avidin which blocks biotin absorption — relevant for high raw egg consumption