Body mass index, iron absorption and iron status in childbearing age women

Abstract

Background: The prevalence of obesity has increased at an alarming rate worldwide. Some studies have observed an association between iron (Fe) deficiency (ID) and obesity, however more research is needed.

Objective: To assess whether body mass index (BMI) is associated with both Fe absorption and Fe status.

Methods: A cross sectional sample of 318 Chilean childbearing age women was studied. The women received either a single dose of 0.5mg of Fe (n=137, group 1) or 3mg of Fe plus ascorbic acid (1:2 molar ratio) (n=181, group 2), both as FeSO4 with labeled radioisotopes. Fe absorption was assessed through radio Fe erythrocyte incorporation. Fe status was determined by hemoglobin (Hb), mean corpuscular volume, serum Fe, total iron binding capacity, transferrin saturation, erythrocyte Zn protoporphyrin and serum ferritin (SF).

Results: 29%, 47% and 24% of the women were classified as normal, overweight or obese, respectively. Fe absorption was significantly lower in obese women (p<0.05). In group 1, the geometric mean and range ±1 SD of the percentage of Fe absorption for normal-weight women was 32.9% vs. 19.7% in obese. For group 2, this percentage was 36% vs. 30%, respectively (2-way ANOVA: BMI classification and Fe dose p<0.05; interaction p=0.34). Although Fe absorption was lower in obese women, they had higher SF (p<0.01) and Hb (p<0.05) concentrations.

Conclusion: Although we did not observe a relationship between BMI and Fe status, obese women displayed lower Fe absorption compared with overweight and normal weight women, possibly due to subclinical inflammation associated with obesity.

Keywords: Body mass index; Hemoglobin; Iron absorption; Obesity; Women.