In view of the results of this study, we expect patients with moderate COPD to experience recurrent episodes of enterocyte damage throughout the day, when walking, dressing, doing the laundry, shopping, cleaning, or performing other activities. They exhibit clearly a lower threshold for developing intestinal compromise during standardized household activities compared with healthy matched control subjects, making this potentially a part of their clinical picture. The functional alterations in the intestines of these patients may result in decreased host defense against bacteria, and increased systemic inflammation as we have discussed. Next, disturbed membrane integrity of mature absorptive enterocytes at the villus tips, as evidenced by IFABP release into the circulation, may reduce the digestive and absorptive capacity of the intestinal tract. Furthermore, the repeated intestinal stress might induce a cellular repair program to restore the damage at the expense of supporting enterocyte absorptive function, possibly leading to temporarily diminished nutrient absorption and metabolic compromise in patients with COPD. In patients with chronic heart failure, a decrease in active and passive carrier-mediated transport for, respectively, 3-O-methyl-D-glucose and D-xylose was shown, indicating dysfunction of transport proteins and diminished intestinal absorptive function, which might be involved in nutritional perturbations that promote cachexia.7,29 We recently reported a negative correlation between IFABP levels and in vivo rates of protein digestion and absorption following an exercise bout in young, healthy subjects, indicating reduced gut absorptive capacity in this situation.30 In addition, evidence was provided for reduced splanchnic extraction of amino acids in patients with COPD,31 potentially implying compromised intestinal function. Future studies including functional tests with, for example, D-xylose or fat absorption tests should be carried out to find a direct link between intestinal compromise and nutrient absorption in COPD. Another consequence of altered intestinal function could be impaired micronutrient absorption, as patients with COPD often exhibit deficits of vitamins such as vitamin D.32 Clinical studies should be performed to assess the effect of intestinal compromise on macronutrient and micronutrient uptake in patients with COPD. Further, practicing food and fluid intake may decrease GI stress during exercise,33 possibly also in patients with COPD in whom it is important to meet energy requirements. In addition, nutritional compounds like the amino acids arginine, glutamine, and citrulline, or lipids may enhance splanchnic perfusion and reduce intestinal damage during physical activity34 or stress situations,35 but effectiveness of these agents in patients with chronic diseases remains to be investigated.