Supplement
Biotin
SaveVitamin B7, a cofactor for carboxylase enzymes in fatty acid synthesis, gluconeogenesis, and amino acid catabolism. Widely marketed for hair, skin, and nails.
Quick verdict
Deficiency is rare in healthy adults eating a varied diet. Supplementation improves brittle nails in some studies but hair/skin claims are overstated for non-deficient individuals.
Evidence score
A rough internal score reflecting quantity, quality, and consistency of human evidence. Not a clinical recommendation.
What the research shows
Brittle-nail studies show improvement at 2.5 mg/day over several months. Hair-loss benefit is only documented in deficiency states. High-dose biotin (>1 mg) interferes with troponin and thyroid lab assays.
Benefits
- Essential cofactor for carboxylase enzymes
- May improve brittle nails over months
- Corrects deficiency-related hair loss
Dosage notes
30 mcg is the Adequate Intake. Nail studies use 2.5 mg/day. Stop high-dose biotin 48–72 hours before lab work.
Side effects
- Lab assay interference at high doses
- Rare skin reactions
Who should be cautious
HIGH-DOSE BIOTIN CAUSES FALSE LAB RESULTS—inform your doctor before blood tests. Especially dangerous for troponin (heart attack marker) assays.
What this page cannot tell you
Most hair/skin/nail marketing targets non-deficient populations where benefit is unproven. Deficiency risk factors include raw egg white consumption, alcoholism, and certain anticonvulsants.
Leaderboard scores
- Longevity20
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