Dietary intake does not account for differences in low iron stores among Mexican American and non-Hispanic White women: Third National Health and Nutrition Examination Survey, 1988-1994

We used nationally representative data from the third National Health and Nutrition Examination Survey (NHANES III) to examine the relationship between low iron stores (serum ferritin < 12 mu g/L) and dietary patterns that might affect iron status among Mexican American (MA) and non-Hispanic white (NHW) girls and women of reproductive age (12-39 y). Dietary data from the qualitative food-frequency questionnaire were used to classify subjects into three categories (using the 25th and 75th quartile values for NHW) for intake of heme iron, nonheme iron, iron absorption enhancers, and iron absorption inhibitors. The prevalence of low iron stores was 17.4% among MA (n = 1368) and 7.9% among NHW (n = 1473). Compared with high intake, the adjusted odds ratio (OR) for low iron stores was 1.80 [95% confidence interval (CI), 1.24-2.62] for medium intake of heme iron and 0.48 (95% CI, 0.25-0.91) for low intake of nonheme iron (plus iron supplement). Compared with no use, use of vitamin C supplements was associated with half the risk of low iron stores (OR = 0.50; 95% CI, 0.29-0.87). Similar results were found after income and parity were controlled for, except that the protective effect of vitamin C supplements was no longer significant. Even after adjustment for sociodemographic and dietary factors, MA women remained at increased risk for low iron stores (OR = 1.80; 95% CI, 1.30-2.49) indicating that the reasons for the higher prevalence of iron deficiency in MA women warrants further investigation.