Glycine is a non-essential, non-polar, non-optical, glucogenic amino acid, which has hydrogen as its side chain. It is the smallest possible amino acid. The chemical formula of glycine is NH2‐CH2‐COOH. Glycine is one of the proteinogenic amino acids. Its codons are GGU, GGC, GGA, GGG of the genetic code. Glycine has numerous proposed uses. Few of those suggested uses have enough evidence to fully back glycine's effectiveness.
Glycine is necessary for central nervous system function. Research has shown that this amino acid can help inhibit the neurotransmitters that cause seizure activity, hyperactivity, and manic (bipolar) depression. Glycine can also be converted to another neurotransmitter, serine, as needed, and may be beneficial in the management of schizophrenia. In one study, twenty-two schizophrenic patients, who did not initially respond to traditional treatments, added glycine to their ongoing antipsychotic medication and found that it significantly reduced their symptoms. Glycine intake among the participants ranged from 40 to 90 grams daily (0.8 grams per kilogram of body weight). More research concerning the effects of glycine on schizophrenia is underway. Studies have shown that glycine also helps improve memory retrieval loss in those that suffer from a wide variety of sleep-depriving conditions, including schizophrenia, Parkinson disease, Huntington disease, jet lag, and overwork.
Results from preliminary studies of glycine as a potential treatment for cancer have been promising, and suggest that it may help prevent the development of cancerous tumors and melanoma. In laboratory mice, dietary glycine prevented tumor growth by inhibiting angiogenisis, the process by which tumors develop their own blood supply. Glycine also seems to play a role in keeping the prostate healthy. In one study, glycine was shown to help reduce the symptoms of prostatic hyperplasia in men.
High-protein foods, such as fish, meat, beans, milk, and cheese, are the best dietary sources of glycine. Glycine is also available in capsule and powder forms, and as part of many combination amino acid supplements. There have been no toxic effects associated with glycine, although some people have reported that taking this supplement causes stomach upset.
Individuals with kidney or liver disease should not consume glycine without consulting their doctor. Taking any one amino acid supplement can cause a disruption of the citric acid or Krebs cycle, and cause a build-up of nitrogen or ammonia in the body, which makes the liver and kidneys work harder to remove waste. Anyone taking antispastic drugs should consult a physician before supplementing with glycine, since it theoretically could increase the effects of these medications.