Calcium Citrate vs. Calcium Carbonate

Q:  In an earlier column you advised taking Tums for calcium, as I've heard other MD's advise. Because I've read several reports on the greater value of calcium citrate, I take a calcium magnesium supplement with calcium citrate. Since it's clear we need magnesium with our calcium, and Tums has no magnesium and the lesser form of calcium, is Tums really the product of choice? It's cheap but that's it. Any comments?

A:  As I wrote in that column, calcium citrate is better absorbed than calcium carbonate but much more expensive. In the article you sent me from the November, 1999 issue of The Journal of Clinical Pharmacology, Howard J. Heller, MD and his colleagues compared the calcium absorption of Citracal (a calcium citrate formulation) and Os-Cal (a calcium carbonate one) after a single oral dose (500 mg calcium), taken with a meal. By measuring blood levels of calcium, they demonstrated that calcium citrate is 2.5 times more bioavailable (easier for your body to use) than calcium carbonate.

Cost is certainly not the most important factor in choosing a calcium supplement, but if a person doesn't have side effects from calcium carbonate, why not take the cheaper one? For some people on a fixed income, an extra $20-30 a month makes a difference. You can buy calcium carbonate combined with Vitamin D and magnesium in pill form too. It doesn't have to be chewable Tums.

"Dear Doctor" is a compilation of patient questions answered by doctors from the Medical College of Wisconsin.