Enhancing iron bioavailability from cereals as a strategy to reduce iron deficiency: in vitro digestion studies and a randomised control trial in UK females

Abstract

Background and hypothesis: Iron deficiency (ID) is the most common nutritional deficiency worldwide, and progress towards prevention of this disorder is slow. Plant foods are important sources of minerals in the United Kingdom. For example, 50% of iron is provided by cereals and a further 15% by vegetables. However, physical encapsulation within plant cells and the presence of absorption inhibitors such as phytic acid limit the availability of iron from plants for absorption in the human small intestine. The overall hypothesis for this project is physical disruption of wheat flour cell walls will increase the release of iron (i.e. the bioaccessibility) from foods during digestion and thereby enhance the bioavailability of iron from wheat-based foods. If successful, this change in milling of flour may provide a strategy to reduce the incidence of ID. Materials and methods: Studies were carried out using wheat flour produced by either standard milling or by micro-milling to reduce flour particle size. Mineral content of foods were determined by ICP-OES. The effects of cooking (boiling and baking), digestive enzymes, and pH on iron bioaccessibility from wheat-based foods following in vitro digestion was measured by ICP-OES. Food digests were applied to intestinal Caco-2 cells and iron bioavailability was assessed using ICP-MS. A human study was also carried out to assess the bioavailability of iron wheat breads made from standard and micronized flour. Results and conclusion: Micro-milling reduced flour particle size by 3-times. Foods made from micronized flour had higher iron bioavailability. This was particularly evident following gastric digestion when pH was low. In summary, the results suggest that micro-milling may increase iron bioaccessibility and bioavailability of iron from wheat flour. If endogenous iron in wheat-based foods was more bioavailable this might decrease the incidence of ID seen in some population groups in the UK.