Prebiotics and iron Bioavailability - Is there a connection?

Poor bioavailability of dietary iron, especially from diets rich in cereals and legumes, is a major factor contributing to the high prevalence of nutritional iron deficiency in developing countries. Dietary modification to increase intake of components that promote iron absorption from low-bioavailability meals is an effective strategy for combating nutritional iron deficiency. Prebiotics are nondigestible oligosaccharides that selectively stimulate the growth and activity of specific species of bacteria in the colon with benefits to human health. Common prebiotics such as inulin and fructooligosaccharides occur naturally in a wide variety of plant-based foods and have recently been suggested to have an enhancing effect on iron absorption. The hypothesis that prebiotics enhance iron absorption is biologically plausible because fermentation of prebiotics by natural microflora present in the colon may decrease the pH of the luminal content, promote reduction of Fe(III) to Fe(II), stimulate proliferation of epithelial cells to expand the absorptive surface area, and potentially stimulate expression of mineral-transport proteins in epithelial cells. However, data available in the literature characterizing the enhancing properties of prebiotics on iron absorption are inconsistent, and mechanisms of actions involved are poorly understood. The notion that the colon can function as a significant site of iron absorption in response to stimulation by prebiotics, and the effect of long-term exposure to prebiotics on the iron status of iron-deficient subjects remain to be clarified. This review discusses the functional properties of prebiotics as a promising dietary factor that enhances iron absorption.