DEAR DR. BLONZ: Calcium citrate and calcium carbonate are sold as supplements to build strong bones and prevent osteoporosis. I would appreciate your help in understanding the advantages or disadvantages of these and other types of calcium supplements. Are they equal in benefits? -- P.S., San Diego
DEAR P.S.: I receive many questions about calcium supplements, and as you point out, there are no shortage of options. The key is to get the calcium from the digestive tract into the rest of the body; that means that the calcium will have to be in solution so that it can pass through the absorptive surface of the intestines. A pill should dissolve in the stomach within 30 minutes if uncoated, or 45 minutes if coated.
Once the calcium compound breaks down, the next step is for it to meet up with the body's vitamin D-dependent calcium binding protein. This protein attaches itself to calcium and escorts it through the intestinal wall. As is obvious by its name, vitamin D is needed to stimulate the production of this binding protein. Although D does not need to be in the stomach at the same time as the calcium, the body has to be adequately nourished with vitamin D for the process to work effectively. The recommended dietary allowance (RDA) for vitamin D is 600 IUs (International Units) per day for those aged 1 to 70, and 800 IUs per day for those over 70. (The body can make its own vitamin D when it's exposed to sunlight, but for those who use sunscreens -- hopefully all of us! -- consuming foods that contain, or are fortified with, vitamin D is important.)
There are many different calcium compounds, each with varying amounts of elemental calcium per unit weight. Be sure to look at the Nutrition Facts or Supplement Facts label on any product, as this will list the actual amount of calcium per serving. The RDA for calcium is 1,000 milligrams per day for those aged 19-50 years of age. Recommended levels for other age groups can be found at: tinyurl.com/nrem7yj.
The calcium in dairy products is readily absorbed; here are some typical calcium-containing compounds found in supplements:
Calcium carbonate: poorest absorption; most calcium per pill (40 percent by weight), which means fewer pills to take; least expensive; most common form of calcium found in supplements; found in antacids. Can cause gastric acid rebound if taken on an empty stomach.
Calcium gluconate and calcium lactate: better absorption, less calcium per pill (9 percent and 13 percent respectively), so more pills needed to get an effective dose; more expensive; less commonly found in supplements.
Calcium citrate and calcium citrate-malate: best absorption; less elemental calcium per pill than carbonate (calcium citrate is 21 percent calcium by weight), so more pills needed; more expensive; gentler to the stomach.
The choice is yours, as any one of these can work as a calcium supplement. It is generally agreed that it is best to take calcium supplements at mealtime.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.