Sarcosine is an amino acid made within the methylation cycle when S-adenosylmethionine (SAM) is conjugated with glycine. It can also be made by catabolism of dimethylglycine (DMG).

There are many dietary sources of sarcosine including eggs, legumes, nuts, and meats.

Sarcosine is also available as an over-the-counter supplement, and it is widely used in cosmetic formulations (toothpaste, creams, and soaps) and detergents. In the methylation cycle, sarcosine is created by the GNMT enzyme, which functions to control SAM excess.

Some clinicians use sarcosine elevation as a marker of ‘excess methyl supplementation’ or ‘over-methylation.’ Currently, there is no literature to support this hypothesis, but rather it is based on physiology. Sarcosine can also be produced through the breakdown of DMG. Sarcosine is a natural glycine transport inhibitor in the CNS, enhancing N-methyl-D-aspartate (NMDA) receptors. NMDA synaptic receptors are not only important for basic CNS functions (breathing, motor function), but also learning, memory, and neuroplasticity.

Decreased NMDA function results in cognitive defects, and overstimulation causes excitotoxicity. Abnormalities in these receptors are implicated in many diseases and targeted for pharmacologic therapy. Sarcosine has been shown to be a co-agonist for NMDA receptors. For this reason, there are many studies evaluating sarcosine as an adjunct treatment for psychiatric diseases, such as schizophrenia, which is characterized by decreased NMDA function.

In addition, using sarcosine to enhance NMDA function can improve depression-like behaviors. Since DMG is essentially sarcosine with an extra methyl group, research shows that they have similar effects. Some studies have evaluated urinary and serum sarcosine’s use as a prostate cancer progression marker; however, the data is mixed. These studies are based on nonspecific metabolomic profiling, which followed random metabolite elevation patterns.