Association Between Exercise-Induced Hyperthermia and Intestinal Permeability: A Systematic Review

Background Prolonged and strenuous physical exercise increases intestinal permeability, allowing luminal endotoxins to translocate through the intestinal barrier and reach the bloodstream. When recognized by the immune system, these endotoxins trigger a systemic inflammatory response that may affect physical performance and, in severe cases, induce heat stroke. However, it remains to be elucidated whether there is a relationship between the magnitude of exercise-induced hyperthermia and changes in intestinal permeability. Objective In this systematic review, we evaluated whether an exercise-induced increase in core body temperature (T-Core) is associated with an exercise-induced increase in intestinal permeability. Methods The present systematic review screened the MEDLINE/PubMed and Web of Science databases in September 2016, without any date restrictions. Sixteen studies that were performed in healthy participants, presented original data, and measured both the exercise-induced changes in TCore and intestinal permeability were selected. These studies assessed intestinal permeability through the measurement of sugar levels in the urine and measurement of intestinal fatty acid binding protein or lipopolysaccharide levels in the blood. Results Exercise increased both TCore and intestinal permeability in most of the 16 studies. In addition, a positive and strong correlation was observed between the two parameters (r = 0.793; p < 0.001), and a T-Core exceeding 39 degrees C was always associated with augmented permeability. Conclusion The magnitude of exercise-induced hyperthermia is directly associated with the increase in intestinal permeability.