Iron Contamination in Cereal-based Products in Africa Can Challenge the Accurate Estimation of Iron Intakes

Abstract

Objectives: To characterize the changes in iron content through cereal processing for a better evaluation of iron intakes and its origin. Methods: Most frequently used processing methods of maize, millet, sorghum, barley, wheat and teff were followed (n≥3) in households in Benin, Burkina Faso and Ethiopia. Iron contents in raw materials, intermediary and final products were analyzed by atomic absorption spectrometry. In vitro iron dialyzability studies were performed on final products to characterize iron behavior during digestion. Results: Threshing, decortication, soaking, milling, sieving, fermentation and cooking were the unit operations most often included in traditional processing of cereals. Although decortication or soaking led to iron losses, other processing steps often led to substantial increases in iron contents (3 to 10 times or more) in final products. This contaminant iron came either from the soil or from processing equipments used for decortication and milling or cooking utensils. After in vitro digestion of dishes prepared with iron-contaminated or uncontaminated flours, the contaminant iron was mainly found in the insoluble fraction and thus not likely available for absorption. However, in some cases, a small proportion of the contaminant iron was found in the soluble or dialyzable fractions, suggesting that a very small part could be absorbable. Conclusions: Iron content in “as eaten foods” is the result of gains and losses that occur during processing. Contaminant iron in African cereal-based foods may lead to an overestimation of the satisfaction of iron requirement, implying the necessity to determine the share between intrinsic and extrinsic iron.