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.
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.