Sarcosine is the N-methyl derivative of glycine. Sarcosine is metabolized to glycine by the enzyme sarcosine dehydrogenase, while glycine-N-methyl transferase generates sarcosine from glycine. Sarcosine is a natural amino acid found in muscles and other body tissues. In the laboratory it may be synthesized from chloroacetic acid and methylamine. Sarcosine is naturally found in the metabolism of choline to glycine. Sarcosine is sweet to the taste and dissolves in water. It is used in manufacturing biodegradable surfactants and toothpastes as well as in other applications. Sarcosine is ubiquitous in biological materials and is present in such foods as egg yolks, turkey, ham, vegetables, legumes, etc. Sarcosine is formed from dietary intake of choline and from the metabolism of methionine, and is rapidly degraded to glycine. Sarcosine has no known toxicity, as evidenced by the lack of phenotypic manifestations of sarcosinemia, an inborn error of sarcosine metabolism. Sarcosinemia can result from severe folate deficiency because of the folate requirement for the conversion of sarcosine to glycine. Sarcosine has recently been identified as a biomarker for invasive prostate cancer. It was found to be greatly increased during prostate cancer progression to metastasis and could be detected in urine. Sarcosine levels were also increased in invasive prostate cancer cell lines relative to benign prostate epithelial cells.