Effect of zinc supplementation on magnesium balance

Nutrition Research Newsletter,  Oct, 1994  

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Supplementation with zinc at a dose of 142 mg/day has been shown to decrease intestinal calcium absorption when dietary calcium intake is low (230 mg/day), but not when calcium intake is moderate or high (500 or 800 mg/day). Whether the same dose of zinc reduces the absorption of magnesium is uncertain. In this study, conducted at the Veterans Affairs Hospital in Hines, Illinois, the researchers determined the effect of zinc supplementation on magnesium absorption and magnesium balance in the presence of different levels of calcium intake.

Twenty-one normal male subjects received a controlled diet providing 230, 500, or 800 mg/day of calcium, 250 mg magnesium, and 12.4 mg zinc. Metabolic balance of magnesium and zinc and the absorption of magnesium were determined during a control period and during supplementation with 142 mg zinc as Zn[SO.sub.4].

When data from all the subjects were analyzed together, there was a highly significant decrease in magnesium absorption and magnesium balance during zinc supplementation. When the three individual groups (low, medium, and high calcium intake) were analyzed separately, however, a significant effect of zinc supplementation on magnesium absorption was observed only in the medium calcium intake (500 mg) group.

The authors conclude that zinc supplementation at the dose studied here may contribute to bone loss by decreasing the absorption of both calcium and magnesium. The lack of a significant effect in two of the three study subgroups was probably due to the small sample size in each group.

Herta Spencer, Clemontain Norris, and David Williams, Inhibitory Effects of Zinc on Magnesium Balance and Magnesium Absorption in Man, J American College. Nutrition 13(5):479-484 (Oct 1994)[Reprints: Herta Spencer, MD, Metabolic Research, PO Box 35, VA Hospital, Hines IL 60141]

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