Health Benefits Of Glycine

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Glycine is a nonessential amino acid produced by our bodies from serine. This amino acid possesses a few characteristics that set it apart from other amino acids, the most fascinating perhaps being the fact that it is the smallest and the only achiral amino acid so far discovered. Glycine mainly functions as a nonpolar precursor to proteins and is an ambivalent amino acid, rendering it capable of being inside or outside the protein. ^[1] In the brain, majority of inhibitory neurons utilize glycine as a neurotransmitter in their synapses. Together with glutamate, glycine is a co-agonist for N-methyl-D-aspartate (NMDA) receptors.

Glycine and Inflammatory Disorders

To date, there have an astounding number of clinical trials and studies associating glycine with anti-inflammatory, immunomodulatory, and cytoprotective effects against inflammatory diseases. A review of recent findings by a research team from the University of North Carolina in 2003 notes the protective action of glycine against hemorrhage-, endotoxin-, and sepsis-triggered shock as well as its ability to put off ischemia/reperfusion and cold storage/reperfusion injury in several tissues and organs such as the liver, kidneys, heart, intestines, and skeletal muscles. The list of glycine’s health-promoting and inflammation-warding actions goes on, from its diminishing effect against injury in the liver and kidneys caused by toxins and drugs to its defensive power against peptidoglycan-related arthritis and various types of ulcers in the gastric mucosa brought about by either stress or a range of harmful substances. The research review further elaborates the anti-inflammatory mechanism of glycine in inflammatory cells such as macrophages, where it suppresses the activation of transcription factors and the formation of free radicals and inflammatory cytokines, and in the plasma membrane, where it turns on the chloride channel that stabilizes or hyperpolarizes the plasma membrane potential, holding back the agonist-induced opening of L-type voltage-dependent calcium channels and the consequent elevation of intracellular calcium ion levels. ^[2]

Glycine and Schizophrenia

Due to glycine’s affinity to receptors of NMDA, which mediate glutamatergic neurotransmission and in turn are involved in the pathophysiology of negative symptoms of schizophrenia, the amino acid has been explored by a few studies as a potential ameliorating strategy against schizophrenic negative symptoms. To date, treatments capable of theoretically increasing the function of NMDA receptors through enhancing actions at the glycine cotransmitter site are being developed in the hope that not only negative but also cognitive symptoms of schizophrenia may be improved. In a double-blind, placebo-controlled, crossover treatment trial by Heresco-Levy et al. (1999), who augmented the antipsychotic medications taken by twenty-two treatment-resistant schizophrenic patients with 0.8 g/kg per day of glycine, glycine treatment led to a significant reduction in negative symptoms and an improvement in Brief Psychiatric Rating Scale scores of patients, who manifested good tolerance to glycine administration. ^[3] Javitt et al. (2001) similarly reported significant improvements with respect to negative and cognitive symptoms among schizophrenic patients medicated with high-dose glycine plus antipsychotic treatment. In their study, glycine treatment induced a significant 34% reduction in negative symptoms among study participants and was associated with an 8-fold increase in serum glycine levels. ^[4]

Glycine and Insomnia

According to the study of Bannai et al. (2012), glycine enhances the sleep quality of individuals suffering from insomnia or difficulty in sleeping. In this study, study participants had 25% less than their usual sleep time for three consecutive nights and took either 3?g of glycine or placebo prior to bedtime. Those individuals on glycine treatment manifested reduced fatigue and improved daytime sleepiness, with improvements in psychomotor vigilance. Moreover, glycine appears to modulate certain neuropeptides found in the suprachiasmatic nucleus, which may indirectly explain the role of glycine in improving sleep restriction-triggered occasional sleepiness and fatigue. ^[5]

Glycine and Cancer

Several recent studies have proposed glycine supplementation as an effective preventive approach against cancer caused by carcinogens. Rose et al. (1997) reported that dietary supplementation of glycine prevents an increase in hepatocyte replication resulting from a potent peroxisome proliferator, which is a nongenotoxic carcinogen and tumor promoter. After 3 weeks of glycine administration, basal rates of cell proliferation decreased by 50% and peroxisome proliferator-induced sustained increase in cell proliferation was hindered, possibly through glycine’s inhibition of tumor necrosis factor-alpha production. ^[6] Another research team in 1999 presented findings that indicate that glycine inhibits angiogenesis in tumors and endothelial cell proliferation dose-dependently, thereby preventing tumor growth. In this study, the tumors arising from B16 melanoma cells implanted subcutaneously in experimental mice had 50-75% less size among mice fed with diet supplemented with 5% glycine and 15% casein; the tumors in mice on glycine-supplemented diet also weighed nearly 65% less than the control group. ^[7]