Keratin
Summary
Oral keratin has only a few small, industry-funded trials. A 500 mg keratin formula with vitamins and minerals improved hair and nail measures over 90 days in 50 women, and a feather keratin hydrolysate (500 or 1,000 mg) improved skin measures in women. Evidence is grade D.
Key facts
- Roxlor Global funded the Cynatine hair trial, and Roxlor's General Manager was one of its three authors; the Cynatine skin and knee trials give no funding statement but have the same three authors, including Roxlor's General Manager; the feather keratin trial was fully funded by BCF Life Sciences[1][2][4][3]
- The Cynatine HNS trials paired keratin with vitamins and minerals, so effects cannot be attributed to keratin alone[1][2]
- 4 graded human outcomes on this page
- October 10, 2026
How it works
ProposedHydrolyzed keratin supplies amino acids, notably sulfur-containing ones; the feather keratin hydrolysate studied is at least 83.5% free L-amino acids. How this translates to hair, skin or nail changes in people is not established.[3]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Skin | Grade D | Improved | RCT · n = 99 · 2025 | 2 rows |
| Hair and nails | Grade D | Improved | RCT · n = 50 · 2014 | 1 row |
| Joints | Grade D | Improved | RCT · n = 50 · 2013 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Facial skin aging signs, hair gloss and nail hardness | Improved | Grade D | RCT · n = 99 · 2025 Healthy women aged 35 to 65 with signs of skin aging (multicenter) Form: Feather keratin hydrolysate (at least 83.5% free L-amino acids) · Dose: 500 mg or 1,000 mg per day · Duration: 90 days Both doses improved skin roughness, wrinkles, moisture, elasticity, gloss of skin, hair and nails, and nail hardness versus placebo; fiber anisotropy and density improved only versus baseline, with a trend versus placebo. | 39367631 (opens PubMed)Source [3] |
| Hair loss, hair strength and nail appearance | Improved | Grade D | RCT · n = 50 · 2014 Women Form: Cynatine HNS: Cynatine keratin with vitamins and minerals · Dose: 2 capsules daily providing 500 mg keratin · Duration: 90 days The keratin formula group showed statistically significant improvements in hair (loss, growth, strength, luster) and nail measures compared with maltodextrin placebo. | 25386609 (opens PubMed)Source [1] |
| Skin moisture, elasticity and wrinkles | Improved | Grade D | RCT · n = 50 · 2013 Women Form: Cynatine HNS: Cynatine keratin with vitamins and minerals · Dose: 2 capsules daily providing 500 mg keratin · Duration: 90 days The keratin formula group showed statistically significant improvements in skin moisture, elasticity, wrinkles and appearance compared with placebo. | 23902431 (opens PubMed)Source [2] |
| Knee pain and stiffness in osteoarthritis | Improved | Grade D | RCT · n = 50 · 2013 Men and women with knee osteoarthritis Form: Cynatine FLX · Dose: 500 mg per day · Duration: 60 days Pain scores fell about twice as much as with placebo, with a similar benefit for stiffness (WOMAC and Lequesne indexes). | 23927594 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Solubilized keratin (Cynatine) | Varies[1][2][4] | No absorption data in our sources.[1] | No adverse effects reported in the abstracts.[1][2][4] | Hair, nail, skin and knee trials at 500 mg/day |
| Feather keratin hydrolysate | Varies[3] | Mostly free L-amino acids (at least 83.5%); no human absorption data in the abstract.[3] | No adverse effects reported in the abstract.[3] | Skin aging trial at 500 to 1,000 mg/day |
Studied doses
Doses studied in human trials ranged from 500 mg of solubilized keratin per day for 60 to 90 days to 1,000 mg of feather keratin hydrolysate per day for 90 days.[1][3][4]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Who should be careful
- Pregnancy, breastfeeding and children
- The trials enrolled adults only and give no safety data for these groups.[1][3][4]
- Allergy to the source material
- Keratin supplements are made from animal sources such as poultry feathers; the trials do not report on people with related allergies.[3]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Safety
Keratin is a dietary protein; the trials reported no safety problems, but they were small and short.
- Evidence quality
- A 2026 meta-analysis of commercial hair supplements (including Cynatine HNS) pooled 14 studies of 967 people, but each product has only one or two small trials.[5]
How to read the label
- Label dose vs clinical doseTrials used 500 mg of keratin per day (Cynatine) or 500 to 1,000 mg of feather keratin hydrolysate.[1][3]
- Check what else is in itCynatine HNS contains vitamins and minerals as well as keratin; results for that formula may not apply to keratin alone.[1]
- Branded ingredientsAll human trials cited here tested branded ingredients and were funded or supplied by their makers.[1][3]
Cost per studied dose, without the sales pitch
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
Cost per studied dose
Enter the price, servings and the amount per serving from your label.
Frequently asked questions
Does a keratin supplement help hair?
One 90-day trial of 50 women found a 500 mg keratin formula with vitamins and minerals improved hair loss, strength and luster measures versus placebo; the maker funded it.[1]
Does keratin help skin?
Two small trials reported better skin moisture, elasticity and wrinkle measures after 90 days, one with Cynatine HNS and one with a feather keratin hydrolysate.[2][3]
How much keratin was studied?
500 mg per day in the Cynatine trials and 500 or 1,000 mg per day of feather keratin hydrolysate.[1][3]
Sources
- [1]A clinical trial to investigate the effect of Cynatine HNS on hair and nail parameters.. ScientificWorldJournal, 2014. RCT
- [2]A randomized, double-blind, placebo-controlled clinical trial to investigate the effect of Cynatine(®) HNS on skin characteristics.. Int J Cosmet Sci, 2013. RCT
- [3]The Effects of an Oral Supplementation of a Natural Keratin Hydrolysate on Skin Aging: A Randomized, Double-Blind, Placebo-Controlled Clinical Study in Healthy Women.. J Cosmet Dermatol, 2025. RCT
- [4]A randomized, double-blind, placebo-controlled clinical trial to investigate the effect of Cynatine® FLX on symptoms of osteoarthritis.. J Diet Suppl, 2013. RCT
- [5]Evaluating the Effectiveness of Commercial Oral Supplements for Hair Growth: A Systematic Review and Meta-Analysis.. J Cosmet Dermatol, 2026. meta-analysis
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every evidence row re-read against its PubMed abstract (whole abstract, including methods). Official sources: no NIH ODS or NCCIH page covers keratin supplements. Industry ties via coi.py: Roxlor Global (25386609, PMC4214097), BCF Life Sciences (39367631, PMC11743286); 23902431 and 23927594 have no PMC full text and no funding in PubMed. Excluded: 30237729 (two multi-ingredient formulas compared, no participant count in the abstract, authors employed by Farmoquímica). Retraction, expression-of-concern, erratum and withdrawn checks on all cited PMIDs: none flagged. Page set indexable.