Observational research has found that diets high in antioxidants, fruits, vegetables, and nuts are associated with reduced risk of COPD. Whereas, diets rich in red meat, processed food, and high-sugar carbonated drinks are associated with a higher risk COPD.[1] However, prospective research on increasing antioxidants in the diet has shown conflicting results. One small study in adults with stable COPD shows that increasing consumption of fruits and vegetables by at least 1 portion daily for 3 years seems to modestly improve lung function when compared to no dietary restriction.[2] In contrast, another small study in adults with moderate/severe COPD shows that consuming 5 or more portions of fruits or vegetables daily for 3 months does not seem to affect lung function when compared to consuming 2 portions or less.[3]
There are conflicting reports whether increasing protein improves physical function in COPD. In a small clinical study in older adults (average age of 77 years) with COPD, drinking a nutritional drink (containing 10 grams of whey peptide, along with 5.6 grams of omega-3 fatty acids and antioxidant vitamins and minerals) in addition to mild exercise daily for 12 weeks improved the quadriceps muscle strength and performance on the 6-minute walk test (6MWT) when compared to engaging in exercise without supplementation.[4] However, two small studies in older adults with COPD (average age of 68-69 years), show that in addition to exercise, consuming either 9.3 grams of protein daily for 9 weeks or 19 grams of protein with 49 grams of carbohydrate daily for 8 weeks does not seem to further improve walking or muscle strength when compared to exercise alone.[5][6]