Association of smoking with serum and dietary levels of antioxidants in adults: NHANES III, 1988-1994

Objectives. This study examined the association of smoking with serum levels and dietary intakes of antioxidants in a nationally representative sample. Methods. This study classified 7873 apparently healthy adults aged 17 to 50 years from National Health and Nutrition Examination Survey III (NHANES III) data as nonsmokers or as smokers if their serum cotinine levels were either lower than 14 ng/mL or 14 ng/mL or greater, respectively. SUDAAN software was used for the statistical analysis. Results. Smokers of both sexes had significantly (P < .001) lower serum levels of vitamin C, alpha -carotene, beta -carotene, beta -cryptoxanthin, and lutein/zeaxanthin. Reduction in the serum vitamin E, lycopene, and selenium levels in smokers was slight. Smokers also had significantly lower dietary intakes of vitamin C and beta -carotene. A significant (P<.001) inverse relation was found between serum vitamin C and <beta>-carotene levels and cotinine levels independent of diet effect, and a positive relation (P<.001) was found between serum levels and dietary intakes. Conclusions. Antioxidants appear to have differing declines in serum levels as a result of reduced dietary intakes and the effects of smoking.