Chronic Obstructive Pulmonary Disease: Nutritional Considerations

Most studies of foods and specific nutrients relate to COPD prevention, rather than treatment, and further research is necessary to establish their value. Nutritional interventions must be used along with avoidance of smoking and with appropriate medical treatment. 

The following dietary factors are under investigation for their possible roles in preventing COPD or affecting its course:

• Fruits and vegetables: A number of studies have associated higher intakes of fruits and vegetables with a lower risk for COPD. However, this does not necessarily mean that fruits and vegetables prevent the disease or that lack of intake causes disease.
  
  In a population of smokers, eating at least 4 ounces of fruit and 3 ounces of vegetables daily was associated with a 50 percent lower COPD risk, compared with individuals who ate the least amounts of these foods. Similarly, a slower rate of decline in pulmonary function was found in a general population consuming increased amounts of foods containing vitamin C. However, other studies have not shown an apparent benefit of higher fruit and vegetable intakes on COPD risk, and further clinical trials are necessary to provide a better understanding.
• Omega–3 fatty acids: In human patients with COPD, supplementation with an omega–3–containing supplement for two years significantly improved shortness of breath and reduced the rate of decline in lung function. Other evidence indicates benefits of omega–3 fatty acid supplements on exercise capacity in patients with COPD, in comparison with those on placebo. Additional controlled clinical trials are needed to determine if omega–3 fats reduce the risk or rate of progression of COPD.
• Vitamin E: Some observational studies have found protective effects of dietary (not supplementary) vitamin E intake on lung function. However, in one large study involving over 29,000 subjects, neither vitamin E (50 milligrams per day) nor beta carotene (20 milligrams a day) supplements reduced COPD symptoms. Unfortunately, clinical trials have not yet assessed the value of diets high in vitamin E for reducing COPD risk or decreasing its rate of progression.
• Maintenance of adequate body weight: In several studies, lower than ideal body weight was associated with a greater risk for death from COPD. However, it is not yet clear whether this association is because low body weight increases the risk for COPD or because COPD increases the risk for low body weight.
  
  By some estimates, almost one in four patients with COPD is malnourished. Nutritional supplements are commonly used to correct this condition, but they have no significant effect on lung function or exercise capacity.