Glycine and collagen
Glycine is a third of collagen. One analysis argues the body may not make enough; this is a hypothesis.
Education only, not medical advice. Talk to your clinician before starting a supplement, especially if you are pregnant, take medication or have a condition.
Evidence grade: D (A strong, B good with gaps, C limited or mixed, D early)
The argument
Every third amino acid in collagen is glycine. Meléndez-Hevia and colleagues calculated that the body's capacity to make glycine may fall several grams a day short of collagen turnover needs [1]. This is a metabolic model, not a clinical trial showing better skin or joints from glycine.
Sources
- Meléndez-Hevia et al. 2009, J Biosci. doi.org/10.1007/s12038-009-0100-9
DOIs verified against Crossref and official pages checked on 2026-10-15.