Cysteine
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An amino acid containing sulfur, made by the body and also obtained from protein-rich foods. It is a building block for the antioxidant glutathione.
Why it’s used
Taken by some to support antioxidant status or as part of amino acid or protein-related supplements.
What the evidence says
Direct clinical evidence for free cysteine supplementation in healthy people is limited. Most research on this pathway involves N-acetylcysteine, a related but chemically distinct compound, so its findings do not directly transfer to plain cysteine.
Where we looked
There was no paper to cite here, so this is the search instead — run it yourself and see what we saw.
- PubMed: 157 records · searched August 2026
"Cysteine"[Title/Abstract] AND ("dietary supplements"[MeSH] OR supplementation[Title/Abstract] OR supplement[Title/Abstract] OR supplements[Title/Abstract] OR "oral administration"[Title/Abstract]) AND (randomized controlled trial[pt] OR clinical trial[pt] OR meta-analysis[pt] OR systematic review[pt]) AND humans[MeSH] - PubMed: 118290 records · searched August 2026
"Cysteine"[Title/Abstract]
This says what this database holds under these terms. It is not a finding that no research exists.
Context
Because studies of plain cysteine supplementation are scarce, no consistent dosing protocol has been established in the literature.
Educational information, not medical or safety advice. Consult a professional for allergies or medical concerns.