The Biochemistry Behind Glycine, Healthy Aging, and Methionine Clearance

Glycine is the smallest amino acid and is the building block for some of the most important molecules in the body, including glutathione, the body’s master antioxidant. Because the human body produces glycine, it is considered non-essential. Yet, research indicates that glycine is commonly not synthesized in sufficient quantities for optimal health.

The majority of glycine in the body is used for protein synthesis. It can also act as a neurotransmitter and may help support immune function and cellular health. Beyond these, glycine acts to support healthy aging through several key biochemical pathways related to methionine. 

Emerging evidence suggests that glycine influences longevity through the methionine cycle pathway. Methionine is a sulfur-containing amino acid a key player in the methylation cycle; however, excess buildup of methionine in the body may lead to increased homocysteine levels (hyperhomocysteinemia).  Hyperhomocysteinemia has been associated with increased oxidative stress, hypomethylation of DNA, cellular damage, and increased cardiovascular risk.  

Glycine helps support methionine clearance in the body through the enzyme glycine N-methyltransferase (Gnmt). In animal studies, the activation of Gnmt has been associated with increases in lifespan. One study reported a 9.3% mean lifespan increase in female Drosophila in the presence of Gnmt overexpression. A murine study reported an over 20% increase in lifespan when the animal diet contained approximately 10% of glycine.  

This branch of methionine metabolism also involves the creation of precursors to the synthesis of spermidine. Elevated spermidine levels may positively influence healthy aging. Animal studies have observed increases in lifespan in the presence of elevated spermidine. Research suggests that certain aspects of spermidine production may be dependent on Gnmt, however, Gnmt is not a direct actor in this biochemical process–more research is needed in this potential relationship.  

Evidence also suggests that Gnmt and the production of spermidine may also influence autophagy. Dysregulated autophagy is one of the major hallmarks of aging.  

The Zeitgeist–what’s the buzz about? 

Many researchers have concluded that methionine restriction may support longevity. Yet, a methionine-restrictive diet may also reduce the availability of important amino acids including glycine and taurine. Emerging evidence suggests that glycine supplementation may mimic methionine restriction.  

While more research is needed, particularly in the clinical setting, evidence suggests that glycine may uniquely support healthy aging and optimal methylation pathways through its critical role in the methionine cycle.