Phytate-iron molar ratio and bioavailability of iron in Bangladesh

Abstract

OBJECTIVE: Phytate, an important component of plant origin foods, works as a chelator for mineral nutrients such as iron. Estimating the phytate-iron molar ratio is a traditional method to assess the bioavailability of dietary iron, and a ratio >1 is suggestive of poor absorption of iron through the intestinal mucosa. In Bangladesh, the ratio is considerably higher; nonetheless, the haemoglobin and ferritin status are satisfactory. Hence, we appraised phytate-iron molar ratios and concomitant haemoglobin and ferritin status. METHODS: Dietary intake of iron and phytate was estimated in non-pregnant non-lactating women and school-age children from a nationally representative survey. The phytate-iron molar ratios were estimated. Linear regressions on haemoglobin for the phytate-iron molar ratios and on molar ratios predicting inflammation-adjusted ferritin were performed. RESULTS: The median ratios were 6.12 in women and 5.47 in children, with corresponding haemoglobin concentrations of 12.6 and 12.5 g/dl. Hypothetical lowering of the ratios by ~50% revealed a nominal increment of haemoglobin and ferritin. CONCLUSION: The standard cut-off phytate-iron molar ratio of >1 is inconsistent with the iron and haemoglobin status of the Bangladeshi population. One plausible explanation for the inconsistency is a non-dietary environmental factor—groundwater iron. Isotope studies incorporating the iron from dietary and the drinking groundwater sources are needed to establish a ratio which might better explain iron bioavailability.