Glycine

Glycine is a 7.5–8.0/10 fit for people who want a low-cost sleep, recovery, and glutathione-support tool with a better safety profile than most biohacker compounds, not a stand-alone longevity drug. The cleanest evidence anchors are Soh 2024, which reviewed 50 human studies, including 42 RCTs, and Kumar 2023, which tested GlyNAC for 16 weeks in older adults. Bannai 2012 adds useful context: supports glycine as a sleep-quality amino acid. The practical gap is the same one that shows up across the report: mechanism and early outcomes are more convincing than broad real-world certainty. In practice, Glycine belongs after the basics, works best when the target is specific, and deserves tracking around benefits, side effects, interactions, and cost before it becomes a standing protocol.

✅ Best for: Adults 50+ who want a cheap, low-risk way to support sleep quality and glutathione substrate availability. Low-collagen diets, vegans, vegetarians, and collagen-peptide users have a stronger rationale because glycine is central to collagen structure. Shift workers and travelers may get the fastest payoff from 3 g pre-bed. Older adults exploring GlyNAC for oxidative stress or function should treat Kumar 2023 as promising early evidence, not settled longevity proof.

❌ Avoid if: You expect glycine to work like a prescription sleep drug, a GLP-1, or a stand-alone longevity therapy. Avoid self-directed psychiatric dosing if you take clozapine or other antipsychotics; Evins 2000 did not support glycine added to clozapine. Also avoid unsupervised use if you have primary hyperoxaluria, recurrent oxalate kidney stones, pregnancy, nursing, or complex kidney disease. Glycine is low-risk, but it is not authority-endorsed treatment for insomnia, metabolic disease, schizophrenia, or aging.