Bioavailability of elemental iron powder in white wheat bread

Abstract

Objective: Iron fortification of wheat flour is widely used. In most cases, elemental iron powders are utilized as fortificants due to their lower cost and few, if any, sensory problems. However, their bioavailability is unknown. We aimed to measure the bioavailability of H 2 -reduced elemental iron powder in white wheat bread made from 72% extraction flour. Design: A stable isotope of H 2 -reduced iron powder (mean particle size 15 mm) was used as fortificant in bread prepared from unfortified wheat flour. In all, 12 5-to 7-y-old children were fed bread with 4 mg of H 2 -reduced 58 Fe /100 g of flour. The next day 57 Fe ascorbate was given as reference dose. After 14 days, erythrocytes were analyzed for isotopic enrichment using mass spectrometry. Results: When normalized to 40% absorption of the reference dose, the geometric mean (7range of 1 s.d.) bioavailability of reduced 58 Fe in wheat bread rolls was 6.5% (3.7-11.8). Conclusions: When compared to previous radioiron studies of ferrous sulfate showing 10% absorption from an identical meal in adult women, the relative bioavailability can be estimated at about 65%. However, the bioavailability of this smaller particle size 58 Fe (15 mm) is likely to be higher than that of commercial iron powder (45 mm) although the precise difference cannot be ascertained with current methods. Thus, the bioavailability of commercial elemental iron powders currently used in fortification programs is likely to be substantially lower than that of ferrous sulfate.

The importance of bioavailability of dietary iron in relation to the expected effect from iron fortification

“…A more realistic bioavailability figure would be B50%, or less (Hallberg et al, 1986;Hurrell et al, 2002;Walter et al, 2004;Hoppe et al, 2006). This more realistic figure would lead to an even more pronounced inability to reach the iron requirement.…”

An overview of the role of bread in the UK diet

“…Hydrogen‐reduced iron powder is often used to fortify flour and human intervention studies investigating the bioavailability of iron in this form have provided inconsistent and conflicting results (Roe & Fairweather‐Tait 1999; Walter et al . 2004).…”

Higher bioavailability of iron from whole wheat bread compared with iron‐fortified white breads in caco‐2 cell model: an experimental study

“…It was suggested many years ago that higher iron absorption might compensate for lower iron content, and iron fortification of white flour might therefore carry no additional benefit . Bioavailability of non‐heme iron from different foods varies from 0.7% to 22.9%, and in an experiment using reduced 58 Fe in wheat bread rolls it was 6.5% (3.7–11.8) …”