Evaluating the Bioavailability of Elemental Iron Powders Used for Food Fortification

Elemental iron powders are the most commonly used food fortificants worldwide because they are relatively inexpensive and do not compromise product flavor, color or shelf-life. However, research conducted over the last 45 years on the bioavailability of these powders has yielded highly variable results (from 5% to 145% relative to the standard ferrous sulfate). These discrepancies undermine confidence in the efficacy of various food-grade powders and have discouraged implementation of food enrichment programs worldwide.

Given the high prevalence of iron deficiency in developing countries and the wide use of elemental iron powders in food fortification programs, a thorough evaluation of iron powders currently in use makes good sense. This, in fact, was one of the key recommendations to emerge from an international workshop which SUSTAIN convened in Monterrey, Mexico in 2000 to address decades of confusion over the efficacy of the powders. To help make sense of published data, SUSTAIN prepared an in-depth review of research conducted on the bioavailability of elemental iron powders over the past 45 years (The Usefulness of Elemental Iron for Cereal Flour Fortification: A SUSTAIN Task Force Report, R. Hurrell, et al., Nutrition Reviews, Dec. 2002).

With funding from the Bill & Melinda Gates Foundation, we also launched a major new research initiative to rigorously evaluate the bioavailability of each of the elemental iron powders now in use as food fortificants. Initially each powder was assessed in a series of metallurgic tests to characterize their structures and surface properties. Since no single screening method reliably predicts the efficiency of iron absorption in human subjects, SUSTAIN evaluated the powders with a range of available screening methods. Consistency of results pointed to the powders meriting further evaluations in human studies with a population of mildly iron-deficient volunteers (now underway). The efficacy of the powders being tested will be determined by improvement in iron status over the 9-12 months participants consume iron-fortified diets. This evaluation of elemental iron powders should provide a firm basis for issuing recommendations on the use of elemental iron in food fortification to reduce iron deficiency.

SUSTAIN's attention to iron powder efficacy has helped encourage manufacturers to improve the bioavailability of their products. This, in turn could accelerate the adoption of iron fortification practices in developing countries, leading to far-reaching public health benefits.

Attention to the optimal form(s) of fortificant iron may not alone result in successful fortification initiatives. Also needed are strategies for enhancing iron absorption, particularly from foods containing inhibitory plant components. The cereal staples of developing countries contain such iron inhibitors.

SUSTAIN has thus launched a groundbreaking effort to identify innovative ingredient technologies to enhance iron absorption from staple foods.