Antioxidant nutrients and pulmonary function: The Third National Health and Nutrition Examination Survey (NHANES III)

Recent studies of chronic obstructive pulmonary disease have raised interest in its relation to nutrition. Several dietary antioxidants have been positively associated with lung function in healthy, general population samples. This study considered the separate and joint effects of vitamin C, vitamin E, beta-carotene, and selenium intake and used both dietary assessment and serum biomarkers of antioxidant status. The authors used data from the Third National Health and Nutrition Examination Survey comprising a sample representative of the US population in 1988-1994 (n = 18,162 subjects aged greater than or equal to 17 years). Multiple linear regression analysis examined the separate and joint effects of the antioxidants on the ratio of forced expiratory volume in the first second (FEV1)/height(2) adjusted for covariates. Each of the dietary and serum antioxidant nutrients was significantly associated with FEV1. When they were considered simultaneously (dietary and serum variables considered in separate models), independent associations were observed for most nutrients. Serum beta-carotene was less positively associated with FEV1 in smokers than nonsmokers, while serum selenium had a stronger positive association with FEV1 in smokers. The authors found that higher levels of antioxidant nutrients are associated with better lung function. The finding that the antioxidants differ in both their overall association with lung function and in whether this association varies by smoking status has implications for further research.