Biotin (B7)
The hair-skin-nails vitamin. Worth supplementing if you're actually deficient or running high-dose ALA (which depletes it); largely a marketing fixture otherwise.
Strong in documented deficiency (hair, nails, skin rash all reverse). Strong for nail brittleness specifically (one of the few non-deficiency claims with RCT support — 2.5 mg/day). Hair-growth claims in non-deficient people are weak. Effects: 8–16 weeks for hair / nails.
Biotin is a B-vitamin cofactor for carboxylase enzymes — small but essential roles in fatty acid synthesis, gluconeogenesis, and amino acid metabolism. True biotin deficiency is rare (gut bacteria make some, and dietary need is small), but symptoms when it does occur are striking: hair thinning and loss, brittle nails, skin rash, and neurological symptoms. The 'biotin for hair' market vastly exceeds the actual evidence — most people taking biotin for hair growth aren't deficient and don't benefit. Where biotin matters: documented deficiency (rare), alpha-lipoic acid users (ALA competes for the same transporter and depletes biotin over time), and pregnancy (need rises).
- Form
- Plain D-biotin capsules. Often included in B-complex products.
- Dose
- 30–100 mcg/day RDA-level. 1,000–5,000 mcg (1–5 mg) for hair / skin claims (note: evidence weak in non-deficient people). Up to 10 mg/day used clinically in MS research (under supervision).
- Timing
- Anytime, with or without food.
- Schedule
- Daily.
- Side effects
- Almost none — water-soluble, excreted readily. Acne in some at high doses (mechanism unclear).
- Interactions
- Lab test interference — high-dose biotin can falsely alter immunoassay-based blood tests (thyroid panels, troponin for heart attacks, hormone panels). Stop biotin 2–3 days before scheduled bloodwork. Anti-seizure drugs (phenytoin, carbamazepine) deplete biotin.
- Contraindications
- None significant. Heed the lab-test interference issue around bloodwork.
- Lab markers
- Serum biotin (rarely tested). Urinary 3-hydroxyisovaleric acid (a sensitive functional marker — elevates in deficiency).
- Food sources
- Egg yolks (the richest source, but only when cooked — raw egg whites contain avidin which binds biotin), liver, salmon, almonds, sweet potato, sunflower seeds, mushrooms. Easily met by typical diet.
Pairs with
Alpha-lipoic acid — co-supplement to prevent biotin depletion if running ALA long-term. Collagen, silica, zinc (hair / nail support stack).
within Vitamins