Evidence supporting the use of: Cystine
For the health condition: Hair (loss or thinning)

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Synopsis

Source of validity: Traditional
Rating (out of 5): 2

Cystine is an amino acid that forms from two cysteine molecules linked by a disulfide bond. Its use in supporting hair growth or treating hair loss/thinning is rooted primarily in tradition and the biochemical role of cystine in keratin structure. Hair is composed largely of keratin, a protein rich in cystine-derived disulfide bridges, which contribute to hair’s strength and rigidity. Because of this, cystine has historically been included in hair supplements and “hair tonic” formulations, with the rationale that providing more of this amino acid might support hair health.

However, scientific evidence directly supporting cystine supplementation for hair loss or thinning in otherwise healthy individuals is limited and not robust. Some small studies and anecdotal reports suggest possible benefits when cystine is combined with other nutrients (such as B vitamins or medicinal yeast), but these studies often have methodological weaknesses, lack controls, or use combination products, making it difficult to isolate the effect of cystine itself. There is no high-quality, large-scale clinical trial demonstrating cystine supplementation alone significantly improves hair growth or reduces hair loss. Most professional guidelines for hair loss do not include cystine as a recommended treatment.

In summary, while the use of cystine for hair health is based on a plausible biochemical rationale and historical tradition, scientific validation remains weak, and routine supplementation is not clearly supported by current evidence.

More about Cystine
More about Hair (loss or thinning)

Other health conditions supported by Cystine

Hair (loss or thinning)
Hangover

Products containing Cystine

We currently have no products on Vitabase that contain this ingredient.