Dietary protein digestion and absorption are impaired during acute postexercise recovery in young men.

Background: Previously, we demonstrated that exercise can cause small intestinal injury, leading to loss of gut barrier function. The functional consequences of such exercise-induced intestinal injury on subsequent food digestion and absorption are unclear. The present study determined the impact of resistance-type exercise on small intestinal integrity and in vivo dietary protein digestion and absorption kinetics. Methods: Twenty four young males ingested 20 g specifically produced intrinsically L-[1-(13)C]phenylalanine-labeled protein at rest or after performing a single bout of resistance-type exercise. Continuous intravenous infusions with L-[ring-(2)H(5)]phenylalanine were employed, and blood samples were collected regularly to assess in vivo protein digestion and absorption kinetics and to quantify plasma levels of intestinal fatty-acid binding protein (I-FABP) as a measure of small intestinal injury. Results: Plasma I-FABP levels were increased after exercise by 35%, reaching peak values of 344+/-53 pg/mL compared to baseline 254+/-31 pg/mL (P<0.05). In resting conditions, I-FABP levels remained unchanged. Dietary protein digestion and absorption rates were reduced during post-exercise recovery when compared with resting conditions (P<0.001), with average peak exogenous phenylalanine appearance rates of 0.18+/-0.04 vs 0.23+/-0.03 mmol phenylalanine.kg lean body mass(-1).min(-1), respectively. Plasma I-FABP levels correlated with in vivo rates of dietary protein digestion and absorption (r(S)= -0.57, P<0.01). Conclusions: Resistance-type exercise induces small intestinal injury in healthy, young men, causing impairments in dietary protein digestion and absorption kinetics during the acute post-exercise recovery phase. To the best of our knowledge, this is first evidence that shows that exercise attenuates dietary protein digestion and absorption kinetics during acute post-exercise recovery