The effect of glutamine supplementation on athletic performance, body composition, and immune function: A systematic review and a meta-analysis of clinical trials.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of clinical trials
PubMed 29784526 · doi:10.1016/j.clnu.2018.05.001
What was done
Authors conducted a systematic review and meta-analysis of clinical trials published up to January 2017 across PubMed, Scopus, Web of Science, SID, and Cochrane Central Register of Controlled Trials. They evaluated the effects of glutamine supplementation in athletes aged 18 and older on body mass, lean body mass, body fat percentage, VO2 max, and immune cell markers (lymphocytes, leukocytes, and neutrophils). A total of 47 studies were included in the systematic review, with 25 trials analyzed quantitatively.
What was found
Glutamine supplementation was associated with a statistically significant reduction in body weight (weighted mean difference [WMD] = -1.36 kg, 95% CI: -2.55 to -0.16, p = 0.02). Doses greater than 200 mg/kg body weight were associated with reduced neutrophil counts (WMD = -605.77, 95% CI: -1200.0 to 52.1, p = 0.03). Supplementation with glutamine dipeptide resulted in higher post-exercise blood glucose (WMD = 0.51 mmol/l, 95% CI: 0.18 to 0.83, p = 0.002). No statistically significant effects were observed for lean body mass, body fat percentage, VO2 max, lymphocyte counts, or leukocyte counts.
Why it matters
Despite widespread marketing to athletes for muscle building, endurance, and immune support, pooled trial evidence shows that glutamine provides no meaningful enhancement of aerobic performance, body composition, or general immune function.
Limits
The abstract does not report individual trial sample sizes, participant characteristics, intervention durations, or risk of bias assessments. Significant variation exists in dosing regimens and supplement forms (e.g., free glutamine versus dipeptides), and the reported confidence interval for neutrophil count reduction spans zero despite the reported p-value. Functional performance endpoints beyond VO2 max were not detailed in the abstract.
Cited by
- supports Glutamine supplementation does not produce body composition improvements in young healthy individuals.