Phytate-iron molar ratio and bioavailability of iron in Bangladesh.

Abstract

OBJECTIVEPhytate, 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.METHODSDietary 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.RESULTSThe 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.CONCLUSIONThe 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.