Dietary Factors Influencing Magnesium Absorption in Humans

Decreased Mg intake and low Mg status have been associated with a number of major health concerns such as diabetes mellitus type II, coronary heart disease, and osteoporosis. While information on Mg intake is available, relatively little is known on dietary factors influencing Mg bioavailability. While it is established that Mg absorption is based on a combination of a non-saturable and a saturable pathway, the nature of especially the latter mechanism is not well understood. Recently, stable isotopes have improved techniques available for the determination of Mg absorption from single test meals or supplements. Some inorganic Mg forms such as MgO seem of limited solubility in the intestine, suggesting low bioavailability. Recent studies have further added evidence that some commonly consumed dietary compounds, such as phytate and oxalate, can inhibit Mg absorption, presumably via complexation, preventing absorption from the small intestine. Phytate for example has been shown to decrease Mg absorption by up to 60%, in a dose dependent manner. On the other hand, fermentable dietary fibre, such as fructo-oligosaccharides, have been demonstrated to increase Mg absorption in humans by 10-25%, even though the underlying mechanisms remain to be elucidated. Future studies to investigate factors impacting Mg absorption are warranted.