Dietary glycine is rate-limiting for glutathione synthesis and may have broad potential for health protection
Introduction
While N-acetylcysteine (NAC) is widely recognised for enhancing glutathione synthesis, this review explores whether glycine, another key component of glutathione, might also be rate-limiting in glutathione synthesis.
What did the review examine?
This review examined existing research on the role of glycine in glutathione synthesis and its potential health benefits. The authors examined:
- How dietary glycine levels impact glutathione production.
- Whether low glycine intake limits glutathione synthesis in humans.
- The potential benefits of glycine supplementation beyond glutathione support, including metabolic, cardiovascular, and anti-inflammatory effects.
To explore these questions, the authors conducted a literature review using PubMed, focusing on studies in humans and animals related to glycine metabolism, oxidative stress, and disease prevention.
Findings
Glycine and glutathione production
- Glutathione synthesis depends on three amino acids: cysteine, glycine, and glutamate.
- While cysteine is widely recognised as the primary rate-limiting amino acid, evidence suggests that glycine availability may also restrict glutathione synthesis in certain individuals, especially those on low-protein or vegetarian diets.
- Animal studies show that glycine supplementation increases tissue glutathione levels and improves antioxidant defences.
Metabolic and cardiovascular benefits
- Glycine may enhance insulin sensitivity and reduce oxidative stress in metabolic syndrome and diabetes.
- A study found that glycine supplementation reduced HbA1c levels (a clinical marker of long-term glucose control).
- Higher plasma glycine levels were associated with reduced cardiovascular disease risk in large population studies.
Anti-inflammatory effects
- Glycine influences inflammatory pathways, reducing markers such as TNF-α and IL-6, which are linked to chronic inflammation and ageing.
- It helps protect the liver from alcohol-induced damage and may aid in the prevention of non-alcoholic fatty liver disease (NAFLD).
Additional potential benefits
- Supports endothelial function, which is crucial for heart and vascular health.
- May improve sleep quality through modulation of neurotransmitter pathways.
- Has shown promise in protecting against neurodegenerative diseases.
Why does this matter?
Our modern lifestyle exposes the body to chronic oxidative stress and inflammation, which can accelerate the progression of various diseases. By enhancing glutathione levels and offering broader health benefits, glycine supplementation could offer a simple and effective way to support cellular health.
