Effects of dietary fibers on magnesium absorption in animals and humans.

There is overwhelming evidence that dietary fibers are an important component of human and animal diets and play an important role in human health. Because dietary fibers and some associated substances, such as phytate, have in vitro mineral-binding capacities, they have been thought to impair absorption of minerals such as calcium, iron and zinc, although magnesium absorption seems to be less affected. Indeed, the effect of dietary fibers depends largely on their own nature and characteristics, and also on mineral homeostasis. In 1977 it was observed that resistant starch, a fermentable dietary fiber, could improve Mg absorption in rats. More recently, attention has been focused on other fermentable substrates such as inulin and oligo- or polysaccharides, for their potential prebiotic and health effects. Studies conducted on different types of fermentable carbohydrates have confirmed their beneficial effect on Mg absorption in different animal species. The majority of these studies have also sought to determine the effects of fibers on other minerals such as calcium, iron and zinc. In contrast to the studies with Mg, these studies did not show a consistent effect on the absorption of these minerals. This is due to the particularities of sites and mechanism of Mg absorption. To date, four human studies have been carried out that generally confirmed the enhancing effect of fermentable oligo- or polysaccharides on Mg absorption.