Undernutrition state in patients with chronic obstructive pulmonary disease. A critical appraisal on diagnostics and treatment.

'Undernutrition state' (UNS) is an ominous condition, in particular when associated with chronic obstructive pulmonary disease (COPD). In this review we discuss pathophysiological mechanisms and how UNS is defined and diagnosed. It seems unlikely that COPD-patients with established UNS have similar potential of reversibility (treatability) upon nutrition interventions as patients at a risk of developing such a condition, i.e. patients with low energy/nutrient intake, since pathophysiological, biochemical and metabolic conditions may differ substantially. We summarize the results of 7 of 17 published randomized controlled trials of nutritional supplementation in COPD-patients with defined UNS in the latest Cochrane review (2012). We thus excluded 10 of 17 trials included in review (2012), mostly because those studies also included patients with 'risk of' UNS. The seven included trials exhibit extensive heterogeneity for all studied variables. Most studies did not show beneficial effects of nutritional supplementation, although some reported minor increase in body weight and physical function of unclear clinical relevance. In contrast to the Cochrane review we conclude that it is difficult to draw firm conclusions regarding the effect of nutritional supplements in patients with COPD and UNS. Improved knowledge in this area is of utmost importance and some factors which should be considered in future studies are suggested.