Dietary Iron Bioavailability: Agreement between Estimation Methods and Association with Serum Ferritin Concentrations in Women of Childbearing Age

Abstract

Predictive iron bioavailability (FeBio) methods aimed at evaluating the association between diet and body iron have been proposed, but few studies explored their validity and practical usefulness in epidemiological studies. In this cross-sectional study involving 127 women (18⁻42 years) with presumably steady-state body iron balance, correlations were checked among various FeBio estimates (probabilistic approach and meal-based and diet-based algorithms) and serum ferritin (SF) concentrations. Iron deficiency was defined as SF < 15 &micro;g/L. Pearson correlation, Friedman test, and linear regression were employed. Iron intake and prevalence of iron deficiency were 10.9 mg/day and 12.6%. Algorithm estimates were strongly correlated (0.69&le; r &ge;0.85; p < 0.001), although diet-based models (8.5⁻8.9%) diverged from meal-based models (11.6⁻12.8%; p < 0.001). Still, all algorithms underestimated the probabilistic approach (17.2%). No significant association was found between SF and FeBio from Monsen (1978), Reddy (2000), and Armah (2013) algorithms. Nevertheless, there was a 30⁻37% difference in SF concentrations between women stratified at extreme tertiles of FeBio from Hallberg and Hulth&eacute;n (2000) and Collings&rsquo; (2013) models. The results demonstrate discordance of FeBio from probabilistic approach and algorithm methods while suggesting two models with best performances to rank individuals according to their bioavailable iron intakes.

Keywords: algorithm; iron status; probabilistic approach.

Figure 1

Study flow diagram.

Figure 2

Predicted prevalence of inadequate iron intakes at different dietary iron bioavailabilities, according to the probabilistic approach proposed by Dainty et al. [14]. Values in boxes are prevalence of iron deficiency (serum ferritin < 15 µg/L). Mean dietary iron bioavailabilities of 16% and 19% were estimated for hormonal contraceptive users and non-users, respectively.

Figure 3

Serum ferritin (µg/L) of women classified according to tertiles of bioavailable iron intake (mg/day). n = 127. Bars and whiskers indicate geometric mean and 95% confidence intervals, respectively. * p < 0.05, ** p < 0.01—in comparison to the first tertile, according to multiple linear regression adjusted for age, body mass index, skin color/race, physical activity level, hormonal contraceptives use and menstrual flow intensity level.