Impact of iron on the composition and function of the human gut microbiome

Iron supplements and iron-fortified foods are widely consumed in the UK but only a relatively small quantity of the total iron is absorbed in the duodenum; the majority passes into the colon where it provides iron for growth of bacteria. An increase in the availability of iron in the intestine increases the growth and virulence of many pathogens, and the lactic acid bacteria, which do not have an iron requirement for their growth, are rapidly out-competed. A recent study showed that dietary iron depletion in a murine model of intestinal inflammation was associated with a marked alteration in the intestinal microbiome, and dietary iron fortification led to a predominance of Enterobacteria over Lactobacilli. Substances that bind iron in the large intestine may therefore be beneficial. Other dietary constituents that may have positive health effects when delivered intact to the large intestine include prebiotics and calcium, reported to be protective against colorectal polyps and colon cancer when in the form of calcium carbonate. Therefore a system that deliver iron-binding materials and other substances that may have a positive impact on the colonic environment to the large intestine could have many uses and health benefits. We will test the hypothesis that iron-binding compounds in the large intestine, such as alginate, facilitate the growth of lactobacilli and other bacteria associated with gut health whilst reducing the levels of potential pathogens. The aim of the research of most interest to the industrial partner is to evaluate the effectiveness of a colonic delivery system by subjecting the material to a simulated gastrointestinal digestion and measuring the degree of protection the delivery system confers to the bioactive material.