L-Cysteine

Tier 2 — promising · Hair · Skin · Glutathione · Detox

The conditionally essential amino acid serving as the rate-limiting substrate for glutathione synthesis. While NAC is better absorbed and more studied, L-cysteine offers a cost-effective alternative with comparable antioxidant and hepatoprotective benefits at adequate doses. RCTs at 400–800 mg/day show improvements in hair shaft diameter and tensile strength. Also used in mucolytic and liver-protective protocols. Dietary cysteine often falls short during oxidative stress, illness, or intense training.

Dose: 500–1,500 mg/day in divided doses with food