Exertional heat stress disrupts gastrointestinal permeability and, through subsequent bacterial translocation, can result in potentially fatal exertional
heat stroke.
Glutamine supplementation is a potential countermeasure although previously validated doses are not universally well tolerated. Ten males completed two 80-minute subclinical
exertional heat stress tests (EHSTs) following either
glutamine (0.3 g kg FFM-1) or placebo supplementation. Small intestinal permeability was assessed using the
lactulose/
rhamnose dual
sugar absorption test and small intestinal epithelial injury using
Intestinal Fatty-Acid Binding Protein (I-FABP). Bacterial translocation was assessed using the total 16S
bacterial DNA and Bacteroides/total 16S
DNA ratio. The
glutamine bolus was well tolerated, with no participants reporting symptoms of gastrointestinal intolerance. Small intestinal permeability was not influenced by
glutamine supplementation (p = 0.06) although a medium effect size favoring the placebo trial was observed (d = 0.73). Both small intestinal epithelial injury (p < 0.01) and Bacteroides/total 16S
DNA (p = 0.04) increased following
exertional heat stress, but were uninfluenced by
glutamine supplementation. Low-dose acute oral
glutamine supplementation does not protect gastrointestinal injury, permeability, or bacterial translocation in response to subclinical
exertional heat stress.