Calcium Debate Rages On

(HealthScoutNews) -- Although a new study tries to settle the debate over which kind of calcium supplement works better, don't hold your breath for the final word on the issue.

Researchers at Creighton University in Nebraska say their tests on 24 post-menopausal women shows calcium citrate, sold as Citracal by Mission Pharmacal, wasn't absorbed any better than calcium carbonate, sold as Os-Cal by GlaxoSmithKline.

Calcium carbonate contains 40 percent pure calcium compared with 21 percent in calcium citrate, but experts say calcium carbonate has to be taken with food to be absorbed well.

The latest finding seems to contradict earlier research at the University of Texas Southwestern Medical School, which found the bioavailability, or absorption rate, of Citracal was at least 20 percent better. The maker of Citracal sponsored that research.

At stake is the $1 billion-a-year calcium supplement market, which is expected to increase as baby boomers age.

Experts outside the fray say both sides in the debate make good points, and what matters most is that any extra calcium helps stave off bone loss as you age.

The latest study, reported in the June issue of the Journal of the American College of Nutrition, was funded by the maker of Os-Cal. Author Dr. Robert Heaney, of Creighton University's Osteoporosis Research Center in Nebraska, says his study mirrors what others have found.

Heaney's team of researchers gave 24 women in their late 50s and early 60s four different treatments over 22 days: 500 milligrams of Os-Cal, 500 milligrams of Citracal, 500 milligrams of plain calcium carbonate and placebos. To equalize levels of vitamin D, which aids calcium absorption, all the women given a special supplement the week before and during the study. The calcium supplements were given with a light breakfast. Blood tests showed all three calcium sources were absorbed identically.

"I think it's very important to point out that I'm not the only person who's found this," says Heaney, a leading calcium and bone researcher.

Dr. Howard Heller, the lead researcher for the University of Texas studies, says the reason why the results are different may be the vitamin D supplements.

"I've found that if you have lower levels of vitamin D in your blood, there's a huge difference in the supplements," says Heller, an assistant professor of internal medicine at the Texas medical school. But when vitamin D levels are higher, he says the differences become statistically insignificant. Heller also says women on hormone replacement therapy had identical absorption rates with calcium citrate and calcium carbonate. Estrogen is believed to help fight bone loss.

"It's something we need to look into, and it might explain the contradictory results between different studies," Heller says. "It may be that whatever happens when you don't have enough estrogen or your vitamin D levels are on the lower half of normal, you're affected more by the carbonate. The main difference is the estrogen and vitamin D supplements. I think this calls for further research because this uncovers something completely new."

But another calcium researcher says Heaney's study should put the matter to rest.

"I've never been persuaded that calcium citrate is absorbed more superiorly," says Connie Weaver, head of the Foods and Nutrition Department at Purdue University. "I think [the study] is really well done and excellent. It really contributes to the general knowledge [on calcium supplements]. Actually, I think this paper helps sort it out."

Bone specialist Dr. Steven T. Harris of the University of California, San Francisco, takes the debate one step further. He says the crucial question is whether absorption rates differ among the elderly, who often take supplements on an empty stomach.

"This study doesn't answer the question in the target group that has been the source of the most heated discussion," he says.

No matter which side you believe, Heaney says the most important thing is to get more calcium into your body any way you can to prevent bone loss.

"They're all good products, but I do object to advertising that says one is better than the other," he says. "The real emphasis here is that the American public needs to know about the bioavailability of all the products they take."

Dr. C. Conrad Johnston, president of the National Osteoporosis Foundation, agress that calcium is calcium. "Usually, we give them enough supplement that a little bit of difference in absorption doesn't mean much. If you give them enough, it doesn't mean much."

Older women should take 1,500 milligrams of calcium daily to prevent bone loss and ward off fractures. Roughly 28 million middle-aged and older Americans are at risk for osteoporosis, the foundation says.

For a definitive conclusion on the relative merits of various calcium supplements, Heaney suggests and Heller agrees with having the National Institutes of Health shepherd side-by-side tests of all the major calcium supplements on the market and publishing the results.

"We just ought to have that data. Otherwise, people are going to be whipsawed by advertising. Who else is going to be above taint?" Heaney says. "But I think you would still have folks saying, 'They didn't treat my product right.'"

What To Do

One thing to note when you're deciding which calcium supplement is right for you: Most experts agree that calcium citrate is better if you're prone to kidney stones.

To learn more about calcium and bone loss, check the National Osteoporosis Foundation.

Read about this study from Tufts University on how a calcium supplement and vitamin D helped prevent bone fractures in older people.

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