Insights into the ethnic differences in serum ferritin between black and white US adult men

Abstract

Although higher serum ferritin (SF) concentrations have been consistently observed among blacks, despite their lower hemoglobin (Hb) concentrations compared with whites, few studies attempted to explain this SF difference. To determine the possible factors contributing to the observed SF difference between blacks and whites, 1,938 non-Hispanic white (NHW) and 1,616 non-Hispanic black (NHB) male subjects, aged 20-65 years were selected from the third National Health and Nutrition Examination Survey (NHANES III). Multiple regression analysis was used to examine the contribution of dietary, biochemical, and socioeconomic variables to the observed SF difference between the two groups. NHB subjects showed a continuing, significantly higher SF concentration compared with NHW subjects at each age group. Age, serum total protein, mean cell volume (MCV), and gamma glutamyl transferase (GGT) were positively associated with SF, whereas percent energy from carbohydrate and fat, calcium intake, serum alpha-carotene, and iron binding capacity (TIBC) were inversely associated with SF (P < 0.01). After excluding subjects with abnormal serum total protein, TIBC and GGT levels from the analysis (the final regression model), the SF difference dropped to 3.95 microg/l (initial difference = 37.1 microg/l) between NHWs and NHBs. The results suggest that the oft-noted black-white SF difference is a result of factors including overall nutrition and health, iron status, and hepatic well-being. Higher SF, low Hb, and reduced TIBC level observed in blacks are consistent with the definition of anemia of chronic disease (ACD). Future investigations are needed to confirm the role of ACD in the black-white SF difference.