Dietary supplement use has steadily increased over time since the 1970s; however, no current data exist for the U.S. population. Therefore, the purpose of this analysis was to estimate dietary supplement use using the NHANES 2003-2006, a nationally representative, cross-sectional survey. Dietary supplement use was analyzed for the U.S. population (≥1 y of age) by the DRI age groupings. Supplement use was measured through a questionnaire and was reported by 49% of the U.S. population (44% of males, 53% of females). Multivitamin-multimineral use was the most frequently reported dietary supplement (33%). The majority of people reported taking only 1 dietary supplement and did so on a daily basis. Dietary supplement use was lowest in obese adults and highest among non-Hispanic whites, older adults, and those with more than a high-school education. Between 28 and 30% reported using dietary supplements containing vitamins B-6, B-12, C, A, and E; 18-19% reported using iron, selenium, and chromium; and 26-27% reported using zinc- and magnesium-containing supplements. Botanical supplement use was more common in older than in younger age groups and was lowest in those aged 1-13 y but was reported by ~20% of adults. About one-half of the U.S. population and 70% of adults ≥ 71 y use dietary supplements; one-third use multivitamin-multimineral dietary supplements. Given the widespread use of supplements, data should be included with nutrient intakes from foods to correctly determine total nutrient exposure.

Background Changes in serum 25-hydroxyvitamin D (25OHD) concentrations in the US population have not been described. Objective Use data from the National Health and Nutrition Examination Surveys (NHANES) to compare serum 25OHD concentrations in the US population in 2000–2004 versus 1988–1994, and to identify contributing factors. Design Serum 25OHD was measured with a radioimmunoassay kit in 20,289 participants in NHANES 2000–2004 and 18,158 participants in NHANES III (1988–1994). Body mass index (BMI) was calculated from measured height and weight. Milk intake and sun protection were assessed by questionnaire. Assay differences were assessed by re-analyzing 150 stored sera specimens from NHANES III with the current assay. Results Age-adjusted mean serum 25OHD concentrations were significantly lower by 5–20 nmol/L in NHANES 2000–2004 than in NHANES III. After accounting for assay shifts, age-adjusted means in NHANES 2000–2004 remained significantly lower (by 5–9 nmol/L) in most males, but not in most females. In a study subsample, accounting for the confounding effects of assay differences changed mean serum 25OHD by ~10 nmol/L, while accounting for changes in the factors likely related to real changes in vitamin D status (BMI, milk intake, and sun protection) changed means by 1–1.6 nmol/L. Conclusions Overall, mean serum 25OHD was lower in 2000–2004 than 1988–1994. Assay changes unrelated to changes in vitamin D status accounted for much of the difference in most population groups. In an adult subgroup, combined changes in BMI, milk intake and sun protection appeared to contribute to a real decline in vitamin D status.