“Cysteine?”Here!
Hasn’t appeared in a scanned product yet.
As a supplement
Talk to your doctor or pharmacist.
Roll Call does not check drug interactions or assess personal safety.
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: 21717 records · searched September 2026
"Cysteine"[Title/Abstract] AND (review[pt] OR "safety assessment"[Title/Abstract] OR "risk assessment"[Title/Abstract] OR toxicology[Title/Abstract] OR toxicity[Title/Abstract] OR characterization[Title/Abstract] OR characterisation[Title/Abstract]) - PubMed: 157 records · searched September 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: 118721 records · searched September 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.
Rumors
Cysteine supplements interfere with insulin and should be avoided by people with diabetes.
We haven’t found evidence strong enough to support this or rule it out.
What was measured is not yet noted.
Who’s saying this
- University of Rochester Medicine — a university or research body: academic health system providing patient care, research and education
How we know who this is
- “University of Rochester Medicine unites our entire health system—hospitals, providers, research, and education—under a single, trusted name.” (their page)
- University of Rochester Medicine — a university or research body: academic health system providing patient care, research and education
L-cysteine supplements promote healthy skin, hair and nails.
We haven’t found evidence strong enough to support this or rule it out.
What was measured is not yet noted.
Who’s saying this
- Swanson Vitamins — a brand: sells its own vitamins and supplements
How we know who this is
- “At Swanson Vitamins, integrity means you get exactly what's promised: Safe, pure, effective supplements that you can trust.” (their page)
- Swanson Vitamins — a brand: sells its own vitamins and supplements
L-cysteine supplements support liver function and detoxification by boosting glutathione.
We haven’t found evidence strong enough to support this or rule it out.
What was measured is not yet noted.
Who’s saying this
- 1MD Nutrition — a brand: sells physician-formulated health supplements; featured doctors are paid partners
How we know who this is
- “Shop 1MD Nutrition’s best selling products, designed by top doctors and scientifically proven to make a difference.” (their page)
- “All doctors mentioned and/or featured on this site are paid partners of 1MD Nutrition®.” (their page)
- 1MD Nutrition — a brand: sells physician-formulated health supplements; featured doctors are paid partners
L-cysteine relieves respiratory symptoms by keeping airway mucus at a normal thickness.
We haven’t found evidence strong enough to support this or rule it out.
What was measured is not yet noted.
Who’s saying this
- 1MD Nutrition — a brand: sells physician-formulated health supplements; featured doctors are paid partners
How we know who this is
- “Shop 1MD Nutrition’s best selling products, designed by top doctors and scientifically proven to make a difference.” (their page)
- “All doctors mentioned and/or featured on this site are paid partners of 1MD Nutrition®.” (their page)
- 1MD Nutrition — a brand: sells physician-formulated health supplements; featured doctors are paid partners
L-cysteine relieves hangover symptoms.
Supports — suggestivehealth and safety evidence
Measured as an outcome.
- L-Cysteine Containing Vitamin Supplement Which Prevents or Alleviates Alcohol-related Hangover Symptoms: Nausea, Headache, Stress and Anxiety (Peer-reviewed) · Funding not checked
- An amino acid alleviates hangover symptoms (Journalism) · Funded by Catapult Cat (industry)
Who’s saying this
- University of Helsinki — a university or research body: research and higher education
How we know who this is
- “The University of Helsinki is Finland’s largest and oldest academic institution.” (their page)
- “The University of Helsinki is an international research community of over 40,000 students and staff.” (their page)