Interactions between magnesium and iron. In vitro studies.

In vitro experiments were performed to study the effects of magnesium (Mg) on the absorption of iron (Fe), which have been reported in the literature. Both poorly soluble Mg compounds (Mg oxide and Mg trisilicate) and a readily soluble Mg salt (Mg aspartate hydrochloride trihydrate) were studied along with ferrous gluconate. The influence of the addition of Mg aspartate hydrochloride, Mg oxide and Mg trisilicate on the pH of aqueous acidic solutions was examined initially. As expected, the Mg salts employed as antacids (Mg oxide and Mg trisilicate) were found to have a potent neutralising effect, while after the addition of Mg aspartate hydrochloride the pH value was only slightly shifted toward the alkaline side. These findings suggest that Mg aspartate hydrochloride--unlike Mg oxide and Mg trisilicate--has no appreciable influence on Fe absorption, as the availability of Fe salts in the intestinal tract is pH dependent. A procedure simulating the physiological variations of the pH value in the gastrointestinal tract was used to determine the Fe and Mg content in the supernatant after the addition of the above Fe and Mg salts to aqueous solutions. The addition of poorly water-soluble Mg compounds was shown to result in a drastic reduction in the amount of Fe contained in the supernatant. These data are in agreement with those reported in the literature. However, no decrease in the amount of dissolved Fe was noted in the presence of Mg aspartate hydrochloride. These findings confirm that poorly water-soluble Mg compounds have a high capacity to adsorb Fe and, thus, interfere with Fe absorption.(ABSTRACT TRUNCATED AT 250 WORDS)