Race-Ethnicity Is Related to Biomarkers of Iron and Iodine Status after Adjusting for Sociodemographic and Lifestyle Variables in NHANES 2003-2006

The NHANES 2003-2006 has assessed iron and iodine status, 2 trace element nutrients of continued public health interest, in the U.S. population. We investigated associations of sociodemographic (age, sex, race-ethnicity, education, income) and lifestyle (smoking, alcohol consumption, BM I, physical activity, dietary supplement use) variables with the iron status indicators serum ferritin, soluble transferrin receptor (sTfR), and body iron in women aged 20-49 y (n = 2539, 2513, and 2509, respectively) and with urine iodine, a biomarker of iodine intake, in adults aged y (n = 3066). Significant correlations between the study variables and biomarkers were weak (vertical bar r vertical bar <= 0.24). Urine creatinine (uCr) was Moderately significantly correlated with urine iodine (r= 0.52). The individual variables explained <= 5% of the variability in biomarker concentrations in bivariate analysis. In multiple regression models, sociodemographic and, lifestyle variables together explained 4-13% of the variability in iron indicators and 41% of the variability in urine iodine (uCr in the model). The adjusted estimated body iron was similar to 1 unit (mg/kg) lower in non-Hispanic black vs. non-Hispanic white women and similar to 1 unit higher in women who smoked vs. those who did not and in women consuming 1 vs. 0 alcoholic drinks/d. The adjusted estimated urine iodine concentration (uCr in the model) was 34% lower in non-Hispanic blacks vs. non-Hispanic whites, 22% higher in supplement users vs. nonusers, and 11% higher with every 10-y increase in age. In summary, after adjusting for sociodemographic and lifestyle variables (and uCr in the iodine model), race-ethnicity retained a strong association wilt sTfR, body iron, end urine iodine; smoking and alcohol consumption with iron biomarkers; and supplement use and age with urine iodine.