Keratin (Hydrolyzed)
Commonly used for
Skin, Hair & Nails
Where to Buy
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The cheapest product is usually low quality, but more expensive doesn’t always mean better.
What is it? / Overview
Hydrolyzed keratin supplies cysteine-rich peptides and amino acids that are the structural building blocks of hair and nails. A small industry-sponsored RCT found improved hair and nail strength and appearance versus placebo, but a broader JAMA Dermatology systematic review found the overall evidence base for hair-loss supplements limited and low-quality, so treat this as a modest, not definitive, benefit.
How is it used? / Administration
Form: Solubilized/hydrolyzed keratin (e.g. Cynatine, from wool keratin), often combined with vitamins/minerals -- cysteine-rich
Typical dose studied: ~500 mg/day hydrolyzed keratin, as used in the main supporting trial
Timing: Daily; hair/nail outcomes typically assessed over ~90 days
New or significant hair loss should be evaluated for nutritional (iron, thyroid) or medical causes before assuming a supplement alone will fix it.
How well does it work? / Evidence
? Emerging / limited evidence
Who should avoid it?
Already taking it? Reasonable to continue if genuinely helping -- worth confirming that nutritional or medical causes of hair/nail changes (iron, thyroid) have been ruled out first, since the main supporting trial is small and industry-sponsored.
Research & references
Beer C et al. (2014). A Clinical Trial to Investigate the Effect of Cynatine HNS on Hair and Nail Parameters. TheScientificWorldJournal. Drake L et al. (2023). Evaluation of the Safety and Effectiveness of Nutritional Supplements for Treating Hair Loss. JAMA Dermatology.
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