What it is
L-Cysteine is a non-essential sulfur-bearing amino acid used to synthesize glutathione, taurine, and keratin. Unlike NAC, it is not acetylated and absorbs more readily into structural tissues.
Supplement · Amino Acid & Sulfur Donor
L-Cysteine
Cysteine (non-acetylated)
500–2000 mg · vegan · gluten-free · 60 caps
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How it works
Cysteine donates sulfur to keratin disulfide bonds (hair and nail strength), feeds the glutathione synthesis pathway, and supports hepatic phase-II conjugation reactions.
Who should take it
Adults with brittle hair or nails, low-glutathione phenotypes, mild liver-burden states. Pair with biotin for keratin or with NAC for glutathione.
Avoid / careful
Cystinuria. Take separately from high-dose vitamin C to avoid oxidation.
When to take it
Morning
Noon
Evening
Night
How to take it
With food
Empty stomach
Before food
FAQs
Frequently asked
Can L-Cysteine help with hair loss?
L-Cysteine provides sulfur for keratin, the protein in hair. Supplementation may improve hair strength and reduce brittleness, but it does not directly address all causes of hair loss.
How does L-Cysteine compare to NAC?
NAC (N-Acetylcysteine) is a more stable precursor to glutathione. L-Cysteine is not acetylated and may be absorbed more readily into structural tissues like hair and nails.
Is L-Cysteine safe for long-term use?
When taken within recommended doses, L-Cysteine is generally considered safe for long-term use in healthy adults. Consult a healthcare professional for personalized advice.
Research summary
A plain-English read of the literature behind this supplement. Not a clinical recommendation.
Cysteine-rich whey trials show glutathione elevation in healthy adults. Hair-strength benefits are clinical-experience driven; rigorous RCT data is limited.
From the blog
Editorial notes
SacredBod's longer take on L-Cysteine — context the structured blocks above don't capture.
L-Cysteine is a amino acid & sulfur donor supplement. L-Cysteine is a non-essential sulfur-bearing amino acid used to synthesize glutathione, taurine, and keratin. Unlike NAC, it is not acetylated and absorbs more readily into structural tissues.
How it works
Cysteine donates sulfur to keratin disulfide bonds (hair and nail strength), feeds the glutathione synthesis pathway, and supports hepatic phase-II conjugation reactions.
Who it’s for
Adults with brittle hair or nails, low-glutathione phenotypes, mild liver-burden states. Pair with biotin for keratin or with NAC for glutathione.
Dosage & timing
- Typical dose: 500–2000 mg
- Best time: morning
- With food: empty-stomach
- Expected onset: 6–12 weeks for hair and nail.
India context
Availability on Amazon India is currently limited or import-only for this form. International brands (iHerb, NOW Foods, Doctor’s Best) ship to India with variable customs handling. Local Ayurvedic equivalents may offer overlapping benefits.
Safety
Cystinuria. Take separately from high-dose vitamin C to avoid oxidation.
Added to your stack.