What it is

Capsules of keratin protein, usually from wool or feathers, sometimes with vitamins and minerals. Not the same as salon keratin smoothing treatments.

How it works

Digested keratin is broken into amino acids like any dietary protein. Any benefit would then come from the vitamins and minerals in the capsule or a placebo effect, unless shown otherwise.

What the studies show

A 90-day placebo-controlled trial of 500 mg of a branded keratin with vitamins and minerals in 50 women reported significant improvements in hair and nail measures. The abstract gives no numbers, the ingredient is branded and the trial has not been independently replicated. Beer 2014
A meta-analysis of 14 commercial supplement studies (967 people), including this one, found better telogen and anagen density than placebo but no significant change in total hair count (p=0.06). Brand-sponsored trials dominate. Alanazi 2026

Side effects and safety

No safety signal in the trials we read.

Bottom line

Interesting but unproven. Adequate protein does the same job for less money. Discuss with a doctor.

Studies 2

Beer C et al. A clinical trial to investigate the effect of Cynatine HNS on hair and nail parameters. 2014

Design: rct
People: 50
Duration: 90 days
Who: women

Tested: 500 mg branded keratin with vitamins and minerals vs placebo

Result: Significant improvements in hair and nail measures versus placebo; branded ingredient, small, not independently replicated.

Read the study ↗

Alanazi R et al. Evaluating the Effectiveness of Commercial Oral Supplements for Hair Growth: A Systematic Review and Meta-Analysis. 2026

Design: meta analysis
People: 967
Who: people in 14 commercial hair-supplement studies

Tested: oral hair supplements vs placebo

Result: Gains in anagen density, less telogen and more hairs on pull test; total hair count not significant (p=0.06).