We use essential cookies (authentication, your saved goals/stack) by default. With your permission we’ll also enable privacy-respecting analytics (Vercel Web Analytics, anonymous load-time metrics) and error-replay diagnostics (Sentry — DOM snapshots only when an error fires) so we can fix bugs faster. Learn more about cookies
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 high-quality meta-analyses and randomised trials published 2013–2026 with a typical study size of 967 participants.
Based on 9 studies · 1 meta-analysis · 5 RCTs · 967 total participants
Confidence
Moderate confidenceBy outcome
Only two small, industry-funded RCTs report hair, nail, and skin benefits, with no independent replication and the remaining evidence being topical in-vitro work — a thin, emerging base.
11 trials ongoing or recruiting · 26 completed on ClinicalTrials.gov
3 of the completed trials have posted results
Registered trials show research momentum for Keratin, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Sep 2026
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.
Not studied — avoid.
No significant drug interactions reported; as a protein supplement, interaction risk is low but unstudied. This possible interaction has not been individually evaluated for this supplement; its likelihood and severity are unknown. If you take an anticoagulant or antiplatelet medicine, ask a pharmacist or prescriber before using this product. Do not stop or change prescribed medicines based on this notice.
Tip: Take with food
Keratin has an evidence score of 3/10 — emerging evidence based on 6 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.
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. Reported side effects are uncommon and include mild GI upset. Use caution if any of these apply to you: Pregnancy/breastfeeding (not studied).
Collagen
Likely helpsHydrolyzed peptides that rebuild skin elasticity, reduce joint pain, and strengthen bone density — results build over 8-12 weeks.
Hyaluronic Acid
Mostly mechanism / observationalHolds 1,000x its weight in water. Most strong evidence is for injectable/intra-articular HA in knee osteoarthritis; oral supplementation shows small, inconsistent benefits for skin and joints.
Ceramides
Mostly mechanism / observationalSkin-barrier lipids; small oral phytoceramide RCTs show improved skin hydration, with early signals for elasticity and wrinkles.
Glutathione
Mostly mechanism / observationalThe body's main intracellular antioxidant; supplemental forms are best studied for skin-lightening, with debated oral bioavailability for systemic effects.
Explore: Best supplements for Skin, Hair & BeautyBest supplements for Body Health
Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 9 studies · how we score · editorial policy
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.
Tap node to isolate • Pinch to zoom • Tap edge for research