Glycine — research review 2

...and the mouse data on GlyNAC, a combination of glycine and N-acetylcysteine, is compelling. A study in Nutrients 2022 showed mice receiving GlyNAC lived 24% longer than controls. That’s a significant lifespan extension.

It is, for mice. But human studies are obviously what we really need to focus on. What does the human evidence tell us about glycine’s role, especially for aging?

Well, glycine is a building block for glutathione, which is often called the body's master antioxidant. Glutathione levels decline with age. Supplementing GlyNAC has been shown to improve this deficiency. A Journal of Gerontology A paper from 2023 found GlyNAC supplementation in older adults improved glutathione deficiency, oxidative stress, and mitochondrial dysfunction.

So, it’s correcting some hallmarks of aging. That’s promising. Oxidative stress and mitochondrial dysfunction are key. But what about direct human longevity or specific disease outcomes?

We don't have direct human longevity data. What we do have, from a Clinical and Translational Medicine study in 2021, is that 24 weeks of GlyNAC supplementation corrected glutathione deficiency, oxidative stress, mitochondrial dysfunction, and even improved genomic damage, cognition, and strength in older adults.

Improved cognition and strength – that's quite broad. Are these improvements sustained, and are they clinically meaningful in the long term? What's still unknown?

Exactly. We know dietary glycine, found in protein foods like meat and fish, can be rate-limiting for glutathione synthesis. So consuming whole foods is important. What’s unknown is whether GlyNAC translates to longer, healthier human lifespans, or if these positive markers like reduced oxidative stress truly prevent age-related diseases or mortality in humans over decades. The current human trials are relatively short-term.