Dietary supplement use by US adults: data from the National Health and Nutrition Examination Survey, 1999-2000.

Data from the 1999-2000 National Health and Nutrition Examination Survey, a nationally representative, cross-sectional survey of US health and nutrition, were analyzed to assess prevalence of dietary supplement use overall and in relation to lifestyle and demographic characteristics. Fifty-two percent of adults reported taking a dietary supplement in the past month; 35% took a multivitamin/multimineral. Vitamin C, vitamin E, B-complex vitamins, calcium, and calcium-containing antacids were taken by more than 5% of adults. In bivariate analyses, female gender, older age, more education, non-Hispanic White race/ethnicity, any physical activity, normal/underweight, more frequent wine or distilled spirit consumption, former smoking, and excellent/very good self-reported health were associated with greater use of any supplement and of multivitamin/multiminerals; in multivariable comparisons, the latter three characteristics were not associated with supplement use. Most supplements were taken daily and for at least 2 years. Forty-seven percent of adult supplement users took just one supplement; 55% of women and 63% of adults aged >or=60 years took more than one. These findings suggest that, to minimize possible spurious associations, epidemiologic studies of diet, demography, or lifestyle and health take dietary supplement use into account because of 1) supplements' large contribution to nutrient intake and 2) differential use of supplements by demographic and lifestyle characteristics.