A comprehensive insight into the effect of glutamine supplementation on metabolic variables in diabetes mellitus: a systematic review

Diabetes mellitus is one of the most important threats to human health in the twenty-first century. The use of complementary and alternative medicine to prevent, control, and reduce the complications of diabetes mellitus is increasing at present. Glutamine amino acid is known as a functional food. The purpose of this systematic review is to determine the potential role of glutamine supplementation on metabolic variables in diabetes mellitus. For this review, PubMed, SCOPUS, Embase, ProQuest, and Google Scholar databases were searched from inception through April 2020. All clinical trial and animal studies assessing the effects of glutamine on diabetes mellitus were eligible for inclusion. 19 studies of 1482 articles met the inclusion criteria. Of the 19 studies, nine studies reported a significant increase in serum GLP-1 levels. Also, eight studies showed reducing in serum levels of fasting blood sugar, four studies reducing in postprandial blood sugar, and triglyceride after glutamine supplementation. Although glutamine resulted in a significant increase in insulin production in seven studies, the findings on Hb-A1c levels were inconclusive. In addition to, despite of the results was promising for the effects of glutamine on weight changes, oxidative stress, and inflammation, more precise clinical trials are needed to obtain more accurate results. In conclusion, glutamine supplementation could improve glycemic control and levels of incretins (such as GLP-1 and GIP) in diabetes mellitus. However, more studies are needed for future studies.