Re: Do calcium and magnesium interfere with each other's absorption?

Calcium is absorbed by 2 different mechanisms; one is vitamin D and carrier dependent and the other is not. Magnesium is also absorbed by 2 different mechanisms; one is carrier-mediated and the other is not. Whether vitamin D is involved in magnesium absorption is unknown.

The carrier-mediated systems are responsible for most of the absorption of these minerals when intakes are in the low to normal ranges. It does not appear that the minerals interfere with the carrier mediated absorption mechanism of each other, although there is some potential for interference in the non-carrier mediated mechanisms. This interference is most likely to be found when intakes of one mineral are very high and the other are low. Therefore, as long as intakes are fairly typical, there is little reason to be concerned with potential interference.

Reference: Gropper, Smith and Groff. 2005. Advanced Nutrition and Human Metabolism. Wadsworth Publishing Company.