Jan Philipp Schuchardt and Andreas Hahn* Pages 260 - 278 ( 19 )
Background: Information on the bioavailability of the essential mineral Mg2+ is sparse.
Objective/Method: Evaluation of the present knowledge on factors influencing the bioavailability and intestinal absorption of Mg2+.
Results: Mg2+ is absorbed via a paracellular passive and a transcellular active pathway that involves TRPM6/7 channel proteins. The bioavailability of Mg2+ varies within a broad range, depending on the dose, the food matrix, and enhancing and inhibiting factors. Dietary factors impairing Mg2+ uptake include high doses of other minerals, partly fermentable fibres (e.g., hemicellulose), non-fermentable fibres (e.g., cellulose, lignin), phytate and oxalate, whereas proteins, medium- chain-triglycerides, and low- or indigestible carbohydrates (e.g., resistant starch, oligosaccharides, inulin, mannitol and lactulose) enhance Mg2+ uptake. The Mg2+ dose is a major factor controlling the amount of Mg2+ absorbed. In principle, the relative Mg2+ uptake is higher when the mineral is ingested in multiple low doses throughout the day compared to a single, large intake of Mg2+. The type of Mg2+ salt appears less relevant than is often thought. Some studies demonstrated a slightly higher bioavailability of organic Mg2+ salts compared to inorganic compounds under standardized conditions, whereas other studies did not.
Conclusion: Due to the lack of standardized tests to assess Mg2+ status and intestinal absorption, it remains unclear which Mg2+ binding form produces the highest bioavailability. The Mg2+ intake dose combined with the endogenous Mg2+ status is more important. Because Mg2+ cannot be stored but only retained for current needs, a higher absorption is usually followed by a higher excretion of the mineral.
Mg-absorption, bioavailability, intestinal uptake, meal composition, dietary fibre, oligosaccharides.
Institute of Food Science and Human Nutrition, Leibniz University Hannover, Hannover, Institute of Food Science and Human Nutrition, Leibniz University Hannover, Am Kleinen Felde 30, 30167 Hannover