The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review.
Level 1 - systematic review of randomized trials
Systematic review of human intervention studies
PubMed 37851316 · doi:10.1007/s11357-023-00970-8
What was done
A systematic review evaluated the effects of glycine administration across eleven physiological systems in adult humans. Databases were searched for studies involving glycine supplementation or treatment in adults. The review included 52 studies: 18 in healthy populations (durations up to 14 days) and 34 in diseased populations (durations up to 4 months).
What was found
The abstract reports no numerical effect sizes or statistical values. Glycine administration showed the most positive outcomes in the nervous system, including improved psychiatric symptoms with longer-term administration in psychiatric populations and improved sleep in healthy populations.
Why it matters
This review synthesizes human clinical evidence regarding glycine's physiological effects, clarifying where clinical evidence exists and highlighting gaps regarding its proposed geroprotective potential.
Limits
No quantitative findings or dosages are reported in the abstract. Studies in healthy adults were limited to very short treatment durations (up to 14 days), small sample sizes, and a high risk of bias. Trials directly evaluating glycine for preventing, delaying, or reversing ageing in healthy humans are lacking.