Glycine, glutathione and possible health protection
What it found
In people eating low-protein diets, glycine may be the nutrient that limits how much glutathione the body can make.
Animal studies suggest extra glycine raises glutathione levels.
What they found
Studies in people
Low-protein diets in people
Vegetarians and others eating relatively low-protein diets have higher levels of 5-L-oxoproline in their urine. This suggests dietary glycine can limit glutathione synthesis in normally fed people.
Animal and lab studies
Glycine limits glutathione
Tissue glycine levels are lower than the amount needed for the enzyme that makes glutathione. When glycine is too low, a build-up of gamma-glutamylcysteine leads to more 5-L-oxoproline in urine.
Animal studies on supplements
Several animal studies reported that extra glycine raised tissue glutathione levels.
Studies in people and animals
Possible health benefits
The authors suggest extra glycine might improve blood vessel function, prevent heart enlargement, help control metabolic syndrome, prevent diabetes complications, reduce inflammation, protect the liver, and promote sleep.
Other findings
Other roles of glycine
Glycine is used to make porphyrins, purines, creatine, sarcosine and bile salts. It also acts on certain receptors, blocks protein glycation, and helps the liver make pyruvate, which scavenges hydrogen peroxide.
What the authors conclude
“Clinical research is warranted to evaluate the impact of supplemental glycine on glutathione levels and on various health disorders.”
Also in their conclusions
- They say clinical research is warranted to evaluate the impact of supplemental glycine on glutathione levels and on various health disorders.
How it was done
Glutathione is a key antioxidant that fights inflammation driven by hydrogen peroxide. Raising glutathione levels might help prevent or treat conditions caused by oxidative stress, and the authors asked whether glycine supplements could do this.
The authors reviewed the scientific literature using PubMed. They looked at studies on glycine levels, glutathione synthesis, and health effects in people and animals.
What it can’t tell you
- We summarised it from the abstract only.
- This is a review of existing literature, not a new trial. It cannot prove that taking glycine supplements will raise glutathione or improve health in people.
- The animal studies cannot show what happens in people.
Who paid
- Authors work at
- Mid America Heart Institute, MO
The paper
- Title
- Dietary Glycine Is Rate-Limiting for Glutathione Synthesis and May Have Broad Potential for Health Protection
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Abstract only
- Cite
- McCarty MF, O'Keefe JH, DiNicolantonio JJ (2018). Dietary Glycine Is Rate-Limiting for Glutathione Synthesis and May Have Broad Potential for Health Protection. Ochsner journal. doi:10.1021/bi400451mFree full textPubMed 29559876DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error