L-cystine,
does it really help with Improvement in diffuse hair loss and hair growth?
research showsThe 47-person trial combined L-cystine with retinol and gelatin, while the 72-person trial combined it with B vitamins and other ingredients. Every cited human trial tested a combination, and no human hair-loss efficacy trial of L-cystine alone was identified, so the result cannot be attributed to L-cystine. This is an indeterminate rating due to absent single-ingredient human evidence, not a finding of no effect.
ads claimPharmacy hair-nutrition products and direct-import products present “a keratin-building amino acid,” “root nutrition,” “reduced telogen shedding,” and “hair growth.” The public clinical trials concern multi-ingredient medicines or nutritional combinations, not L-cystine capsules alone.
Useful facts when choosing a product
- The key 1989 combination contained L-cystine 70 mg/day, retinol 18,000 IU/day, and gelatin 7 g/day.
- The 1993 trial compared two combinations with different B-vitamin and L-cystine contents.
- Efficacy endpoints included anagen and telogen proportions on trichogram, hair density, and hair swelling.
- The short-term tolerability signal for L-cystine itself was good, but the high-dose vitamin A in the combination has separate safety implications.
Chamgap Semantic Classification Code
Candidate index · review held
UNK.l-cystine.UNK.diffuse-hair-loss-and-hair-growth.improve.placeboUnknown > L-cystine > Unknown > diffuse hair loss and hair growth > Improvement claim > Placebo
An automated migration candidate, not an issued permanent code; exact claim scope remains under review. This machine-generated migration candidate helps retrieval but is not a permanent assignment. The original verdict ID and URL remain authoritative.
What the research actually shows
The 47-person double-blind trial tested L-cystine plus retinol and gelatin, while the 72-person randomized double-blind trial tested L-cystine with B vitamins and other ingredients. Neither included an L-cystine-only arm.
Why this is classified as ?
Every cited human trial tested a combination, with no L-cystine-only arm or standalone efficacy trial. Because ingredient attribution is impossible, no score is assigned and the rating is indeterminate.
Counterpoint. Signals exist for the full formulations, but the single-ingredient contribution is unknown.
Rejudgment record. Reassessment (cross-check reflected) — The only human trials tested a 47-person L-cystine-retinol-gelatin combination and a 72-person combination with B vitamins and other ingredients; no standalone human hair-loss efficacy trial permits attribution to L-cystine, so the rating is indeterminate
Cross-check — AI research and Codex final gate
Evidence Table
| Study | Design | Sample | Funding | Endpoint | Result | Weight |
|---|---|---|---|---|---|---|
| Hertel H et al. 1989 | Pilot clinical study followed by a double-blind placebo-controlled trial | 36 in the pilot and 47 in the double-blind trial | Unknown | Anagen and telogen proportions on trichogram and hair density | The L-cystine, retinol, and gelatin combination was reported to reduce telogen rate by 13.5% and improve anagen rate by 8%. | Key |
| Budde J et al. 1993 | Randomized, double-blind, placebo-controlled comparative trial | 72 women with diffuse hair loss, four months | Included an author affiliated with Agpharm | Hair swelling, frontal/parietal anagen rate, and investigator/participant assessment | Active combination 1 was superior to placebo, and the contribution of additional ingredients was not replaced by higher L-cystine alone. | Key |
Receipt — 2 References
All 2 cited sources were verified for existence at the original page (as of 2026-07-11).
Final verification and publication gate: Codex · Evidence date: 2026-07-11 · Corrections: none
Cite this verdict
[Chamgap] L-cystine x improvement in diffuse hair loss and hair growth — Evidence Grade ?. 2 cited sources checked. Source: https://chamgap.com/en/verdicts/skin-hair/l-cystine-diffuse-hair-loss-growth/ · CC BY 4.0CC BY 4.0 — free to use with attribution; do not distort grades, numbers, or verdict meaning.
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