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Hydrolyzed Keratin
An oral hair, nail, and skin supplement (often the branded 'Cynatine HNS' solubilized keratin). A couple of small, industry-funded RCTs report improved hair and nail parameters, but there is no independent replication and the evidence base is thin.
What the evidence says
Most Keratin studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality randomised trials published 2013–2025 with a typical study size of 50 participants.
Based on 3 studies · 2 RCTs · 50 total participants
Confidence
LowBy outcome
Keratin has an evidence score of 2.5/10 — emerging evidence based on 3 indexed studies. An oral hair, nail, and skin supplement (often the branded 'Cynatine HNS' solubilized keratin). A couple of small, industry-funded RCTs report improved hair and nail parameters, but there is no independent replication and the evidence base is thin. Representative study: PMID 25386609.
The commonly studied dose of Keratin is ~500-1000 mg hydrolyzed/solubilized keratin daily (trial-typical); Cynatine HNS trial used 500 mg keratin plus vitamins/minerals. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Explore: Best supplements for Body Health
Last reviewed June 2026 · evidence from 3 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Keratin is the structural protein of hair, nails, and skin, sold as an oral supplement — most prominently as 'Cynatine HNS,' a solubilized/bioavailable keratin, or as feather-derived keratin hydrolysates. The rationale is that supplying keratin peptides and sulfur-rich amino acids supports keratin synthesis in hair and nails. The reality is a small evidence base dominated by manufacturer involvement: a 90-day RCT of Cynatine HNS reported significant improvements in hair strength, loss, and nail appearance, and a separate RCT of a feather-keratin hydrolysate reported improved skin and nail parameters — but both were industry-funded/affiliated, modest in size, and have not been independently replicated. Mechanistic and cosmetic-formulation studies (e.g., keratin peptides in hair products) are in-vitro/topical and don't speak to oral efficacy. Net: plausible building-block logic, but the human evidence for oral keratin is limited and conflicted.
Supplies keratin peptides and sulfur-rich amino acids proposed to support hair/nail keratin synthesis — a plausible but not clinically-proven oral mechanism.
Hydrolyzed keratin provides free L-amino acids that one trial framed as 'aminobiotics' supporting skin and appendage health.
How Keratin works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
~500-1000 mg hydrolyzed/solubilized keratin daily (trial-typical); Cynatine HNS trial used 500 mg keratin plus vitamins/minerals
Take with food
| Form | Type |
|---|---|
| 💊Solubilized keratin (Cynatine HNS) or feather keratin hydrolysate | Recommended |
| 💊Generic hydrolyzed keratin | Alternative |
Evidence comes from branded, industry-funded products.
Minimum: 8 weeks
Optimal: 13 weeks
Cycling: Not required
Note: With food, daily.
Dose-response data unavailable. The current published research for Keratin does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
A 90-day RCT reported better hair strength/loss and nail appearance versus placebo.
A feather-keratin-hydrolysate RCT reported reduced roughness/wrinkles and better elasticity.
Not studied — avoid.
No significant drug interactions reported; as a protein supplement, interaction risk is low but unstudied.
Tip: Take with food
Biotin is the classic hair/nail supplement and is commonly combined with keratin in formulas.
Layered hair/nail support (modest evidence for each).
Collagen targets skin and connective tissue while keratin targets hair/nails; the two are often stacked.
Complementary skin, hair, and nail support (collagen better evidenced).
The best time to take Keratin is with meals. Take it with food. Taken daily with food as a protein-derived supplement; trials dosed over ~90 days.
Keratin is generally well-tolerated and considered safe for most healthy adults at recommended doses. The most commonly reported side effects are mild GI upset. Use caution if any of these apply to you: Pregnancy/breastfeeding (not studied).
Hydrolyzed peptides that rebuild skin elasticity, reduce joint pain, and strengthen bone density — results build over 8-12 weeks.
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