Study Says Calcium Supplement May Retard Bone Loss

Calcium supplements can retard bone loss associated with osteoporosis, but only in older women who have been postmenopausal for at least five years and who have calcium-deficient diets, a study published in Thursday’s New England Journal of Medicine reveals.

Among women who have been postmenopausal five years or less, calcium supplements appear ineffective in preventing a very rapid phase of bone loss, said Dr. Bess Dawson-Hughes, chief of the calcium and bone metabolism laboratory at the USDA Human Nutrition Research Center on Aging at Tufts University in Boston.

But after about five years, calcium supplements appear to kick in, preventing further bone deterioration.

“That’s where the good news is. If you are out of that rapid dip period, and if you have a low dietary intake, then increasing your calcium to the recommended dietary allowances has a very substantial benefit,” she said.

Past research on the effectiveness of calcium supplements has yielded mixed results because most studies have failed to distinguish between women who are recently postmenopausal and those who are well beyond menopause, Dawson-Hughes said.

As a result, calcium is widely held as important in preventing bone loss, but medical experts have not agreed on the need for supplements.

“You have to look at subsets of the postmenopausal population,” Dawson-Hughes said. “We had enough people here that we could partition them into subsets and thereby develop more of an idea of what was going on.”

The study is clear on two other points. Women who already achieve high calcium intake through their diets do not need supplements. And supplements of calcium citrate malate, a form patented by Procter & Gamble and found in Citrus Hill Plus Calcium orange and grapefruit juices, appeared to be better absorbed than calcium carbonate, the more popular form found in over-the-counter products such as Tums, Dawson-Hughes said.

The study examined 301 healthy, postmenopausal women ages 40 to 70 for two years. Half of the women had a usual dietary calcium intake of less than 400 milligrams a day--about two servings of calcium-rich food. Women with dietary calcium intakes of 400 to 650 milligrams a day made up the second group.

The Recommended Daily Allowance for adults ages 25 and older is 800 milligrams a day, about four servings of a calcium-rich food.

American women, however, rarely achieve the RDA for calcium through diet alone, Dawson-Hughes said.

Calcium is found in milk, yogurt, cheese, canned salmon and sardines, and dark green leafy vegetables such as broccoli, collard greens and kale.

Each group was randomly divided into three subgroups: those who received 500 milligrams of calcium carbonate, those who received 500 milligrams of calcium citrate malate and those who received a placebo. Bone measurements were taken in the neck, spine and forearm.

The results showed that women who had undergone menopause five or fewer years earlier had significant bone loss that was unaffected by supplements in any form.

At menopause, the female hormone estrogen, which helps protect against bone loss, begins to decline rapidly.

“Among recently postmenopausal women, we found that the calcium supplementation didn’t seem to matter,” Dawson-Hughes said.

“The bone seems to be under such strong influence of the body’s dropping estrogen level.”

But after about five years, the supplements appeared to prevent further bone loss in women deficient in calcium.

“The study is encouraging because it suggests that calcium can help prevent bone loss, which has been disputed by some researchers,” said Bonnie Liebman, a nutritionist for the Center for Science in the Public Interest in Washington.

“I don’t think women who have recently undergone menopause should say, ‘I’m not going to worry about calcium for five years.’ ”

But Liebman said the study’s findings that calcium citrate malate was more effective than calcium carbonate deserves follow-up study because the former is generally more costly and available only in Citrus Hill Plus Calcium fruit juices.

The study does not reveal whether calcium carbonate would be more effective in higher doses or if taken with food, Liebman said (the subjects took the supplements without food).

The study found women with lower dietary calcium intake who consumed calcium citrate malate had no significant bone loss.

Women who received calcium carbonate maintained bone density in the hip and forearm but lost bone in the spine.

The women on the placebo lost 2% to 3% of bone density at the hip, forearm and spine over two years. Among women with higher dietary calcium intake, there were no differences among subjects taking either form of calcium supplement or the placebo.

“This fits with the idea that (supplementation) benefits those who are deficient,” Dawson-Hughes said. “But more and more and more is not better and better and better.

“Women in America, in this age range, have an intake of 475 milligrams a day. That’s very little--just over half the RDA--of what they need,” Dawson-Hughes said.

“I would promote the use of calcium-rich foods as a first priority. When a woman is unable to meet the requirements by doing that, using supplements would be your second preferred route.”