Biotin
Vitamin B7/vitamin H, a water-soluble B-vitamin serving as a coenzyme for carboxylase enzymes. Supports keratin production for healthy hair, skin, and nails, and assists in macronutrient metabolism.
Marketing vs Evidence
What brands claim
"Promotes healthy hair, skin, and nails" — found on nearly every beauty supplement label.
What the research shows
Only benefits people with a genuine biotin deficiency, which is uncommon in healthy adults eating a varied diet. No clinical evidence it improves hair or nail growth in non-deficient individuals. Most products dose 10–100× the daily requirement.
What it’s good for
Biotin is a cofactor for carboxylase enzymes involved in keratin protein synthesis. It supports hair follicle stem cell proliferation, improves hair shaft cortex structure, and reduces brittleness. Deficiency causes diffuse alopecia.
Dose: 2500–5000 mcg
Biotin enhances nail plate thickness by stimulating keratinocyte growth and improving the cross-linking of keratin proteins in the nail matrix. Clinical trials show 25% increase in nail thickness with supplementation.
Dose: 2500–5000 mcg