By the way, doctor: Which calcium supplement should I take?

Q Which calcium supplement is better for older women, calcium citrate or calcium carbonate?

A Calcium citrate (Citracal) is probably the better choice for older people. Although calcium carbonate is less expensive — it contains a higher percentage by weight of actual (elemental) calcium — it requires stomach acid for absorption. That means taking it with or soon after a meal. By contrast, calcium citrate is readily absorbed, with or without stomach acid. The distinction may be important if you have achlorhydria, or low stomach acid, which is associated with a variety of age-related conditions. Many calcium carbonate supplements are also poorly soluble, although this problem can be avoided by taking chewable preparations such as Tums or Viactiv.