Magnesium Absorption from Leafy Vegetables Intrinsically Labeled with the Stable Isotope 26Mg

Abstract

Five leafy vegetables were grown in nutrient solutions in which the natural magnesium was replaced by the stable isotope, ²⁶Mg. They were fed to rats in a test meal together with the extrinsic tracer ²⁸Mg: a) to determine to what extent the instrinsic tracer (²⁶Mg) was exchangeable with extrinsic ²⁸Mg during the digestion and absorption processes, and b) measure the relative Mg availability from the different vegetables. The two tracers, ²⁶Mg and ²⁸Mg, were close to 100% exchangeable, as judged by the ratio of ²⁶Mg/²⁸Mg in the livers. Mean relative Mg absorption from the various vegetables ranged from 108 to 118% of the Mg absorbed from a standard test meal containing MgSO₄. There were no statistically significant differences between the rates of Mg absorption from the five vegetables although two of the vegetables tested contained oxalate. The usefulness of stable ²⁶Mg as a tracer in Mg bioavailability tests is discussed.