Nutritional intervention in COPD: a systematic overview.
OBJECTIVE: We conducted a systematic overview of randomized controlled trials (RCTs) to clarify the contribution of nutritional supplementation for patients with stable COPD. METHODS: RCTs were identified from several sources, including the Cochrane Airways Group register of RCTs, a hand search of abstracts presented at international meetings, and consultation with experts. Two reviewers independently selected trials for inclusion, assessed quality, and extracted the data. RESULTS: Twenty-one reports were classified according to the type, duration of supplementation, and the presence of anabolic substances. High carbohydrate meals were associated with an increase in carbon dioxide production and a decrease in exercise capacity. Short-term crossover studies in which diets of various compositions were administered supported the notion that high carbohydrate loads increase the stress on the ventilatory system. The influence of longer-term supplementation (> 2 weeks) on weight, anthropometry, and exercise capacity varied, without there being a consistent effect. Lean body weight was only occasionally reported and health-related quality of life too rarely to be included as an outcome. The influence of recombinant human growth hormone was disappointing. Anabolic steroids increased body weight and lean body mass, but had little influence on exercise capacity. CONCLUSION: This systematic overview in patients with COPD supports the notion that those with marginal ventilatory reserve might benefit from a dietary regimen in which a high percentage of calories are supplied by fat. Although there are reports of the benefits of nutritional repletion, trials of > 2 weeks failed to show consistent benefit on body weight. Evaluating nutritional repletion is hampered by the absence of information regarding body composition, exercise, and health-related quality of life. Growth hormone has not been shown to be useful. Further studies are needed to refine the beneficial effects of anabolic steroids as adjunctive agents together with nutritional support and exercise.