Glycine

Solid evidence for improving subjective sleep quality when taken before bed. Also important as a glutathione precursor, especially in older adults.

A rough internal score reflecting quantity, quality, and consistency of human evidence. Not a clinical recommendation.

Multiple small trials show 3 g of glycine before bed improves subjective sleep quality, reduces next-day fatigue, and may improve sleep efficiency. Glycine + N-acetylcysteine (GlyNAC) supplementation restored glutathione levels and improved several aging biomarkers in a randomized trial of older adults.

• Improves subjective sleep quality at 3 g before bed
• Glutathione precursor supporting antioxidant defense
• Collagen synthesis support

Sleep: 3 g before bed. Glutathione support: 1–3 g/day. Collagen: 5–15 g/day with vitamin C.

• Rare at typical doses
• Sweet taste may be noticeable in powder form

Generally very safe. Theoretical concern at very high doses in schizophrenia treatment (used adjunctively at 30–60 g/day in research).

Sleep studies are small and primarily rely on subjective measures. The GlyNAC longevity data, while promising, comes from a single research group.

• Sleep65
• Longevity50
• Recovery40