A study epublished in January 2015 reported that supplementation with L-glutamine in obese and overweight individuals alters gut microbiota resulting in population changes similar to those seen with weight loss. The Centers for Disease Control and Prevention (CDC) state that 69% of adults age 20 or older are overweight or obese in the U.S.

The subjects included 33 overweight or obese adults ages 23 to 59 years with a body mass index (BMI) between 25.03 and 47.12 kg/m2. The subjects received 30 grams L-glutamine daily or 30 grams of L-alanine daily as the control group for 14 days. The researchers evaluated gut microbiota at the beginning of the study and again after the 14 days supplementation period.

The L-glutamine group showed significant changes in the Firmicutes and Actinobacteria phyla after the supplementation period compared to the control group. In fact, the Firmicutes/Bacteroidetes ratio, a good biomarker for obesity, decreased from 0.85 to 0.57 in the L-glutamine group and increased from 0.91 to 1.12 in the control group. The researchers specifically found reductions in Dialister, Dorea, Pseudobutyrivibrio and Veillonella, belonging to the Firmicutes phylum.

The study authors concluded, “Oral supplementation with L-glutamine, for a short time, altered the composition of the gut microbiota in overweight and obese humans reducing the Firmicutes/Bacteroidetes ratio, which resembled weight loss programs already seen in the literature.”


de Souza Z, et al. Nutrition. 2015 Jan 29.  [Epub ahead of print.]