Why was this study done?

Supplementing with calcium is an effective tool for bone maintenance, but it has long been postulated that high calcium intake may negatively affect other minerals (especially magnesium). This study was designed to investigate the effects of a high calcium supplementation (1500 mg/day for 10 days) on magnesium excretion.

What did the study find?

The study did find that high doses of calcium do increase magnesium excretion, but not enough to be of concern.

Effect of High Calcium Intake on Magnesium Excretion.
Authors: Spiller GA, Jensen CD, Whittam J. FASEB J, 1988. 2(6): p. A1099.
PDF Abstract: FASEB J, 1988.