The impact of consuming iron from non-food sources on iron status in developing countries

Objective: To determine the impact of contaminant iron and geophagy on iron intake and status of persons living in developing countries. Design: Literature for review was identified by searching Medline and Agricola, from appropriate other texts and from three reports from the Opportunities for Micronutrient Interventions (OMNI) Project of USAID. Setting: The dietary intake of iron by people living in developing countries is generally high but iron deficiency remains prevalent. This apparent paradox is because the iron being consumed is predominantly in the non-haem form, which is poorly absorbed. Some of this non-haem iron is from contamination of food with iron from soil, dust and water; iron leaching into food during storage and cooking; contamination during food processing such as milling; and the practice of geophagy. Results: Although the contribution of contaminant iron to overall iron intake is well documented, its absorption and thus its impact on iron status is not. To be available for absorption, contaminant iron must join the common non-haem pool, i.e. be exchangeable. The absorption of exchangeable contaminant iron is subject to the same interactions with other constituents in the diet as the non-haem iron that is intrinsic to food. The limited available evidence suggests wide variation in exchangeability. In situations where a significant fraction of the contaminating iron joins the pool, the impact on iron status could be substantial. Without a simple method for predicting exchangeability, the impact of contaminant iron on iron status in any particular situation is uncertain. Conclusions: Interventions known to increase the absorption of iron intrinsic to foods will also increase absorption of any contaminant iron that has joined the common pool. Any positive effect of geophagy resulting from an increased intake of iron is highly unlikely, due to inhibiting constituents contained in soils and clays. The efficacy of approaches designed to increase the intake of contaminant iron remains encouraging but uncertain. An approach using multiple interventions will continue to be essential to reduce iron deficiency anaemia.