Boston – For years, doctors have been telling older women to take calcium and vitamin D tablets to protect their bones as they age.
Now, the biggest study ever to examine the value of that timeworn advice suggests the supplements convey only limited protection. Calcium and vitamin D failed to protect against most fractures in the mostly low-risk women.
At the same time, the supplements did seem to offer some benefit against hip breaks among women over 60 and those who took the pills faithfully.
The study is “not as ringing an endorsement of calcium as one might like,” said one of the researchers, Dr. Norman Lasser at New Jersey Medical School.
Even so, many experts said they would stand behind federal guidelines recommending the supplements, if needed, to meet standard intake of calcium and vitamin D.
“There’s probably a small benefit,” said Dr. Joel Finkelstein, of Massachusetts General Hospital, who wrote an editorial in the New England Journal of Medicine, where the study appeared today. “It’s a good start, but women at higher risk need to know it’s not enough.”
The findings were an offshoot of the big national study of diet and hormone therapy known as the Women’s Health Initiative.
Osteoporosis touches an estimated 10 million Americans, making their bones prone to break. One in two women will suffer such a fracture in her lifetime.
For women over age 50, federal guidelines recommend 1,200 milligrams of bone-building calcium and 400 to 600 international units of vitamin D daily from diet and, if needed, supplements.
The seven-year study of 36,282 women ages 50 to 79 gave half the participants 1,000 milligrams of calcium and 400 units of vitamin D, while the other half took dummy pills.
However, many were also taking their own supplements before the research began, and they were allowed to keep doing so, whether they were assigned to the test group or the comparison group.
These extra supplements may have helped the women stay healthy but ironically diluted the findings, since any benefit is harder to show against a backdrop of fewer fractures. Also, women in the study were taking hormone pills, likely further cutting the number of fractures.
The study showed better hip-bone density in the group given supplements, but they ranked no better statistically in avoiding fractures of all kinds. However, women over age 60 reduced their chances of hip fracture by 21 percent with the supplements.
Many women sometimes missed their daily dose – a common phenomenon in real-world testing – but those who took their supplements most faithfully lowered their risk by 29 percent.
“We still do believe … that maintaining an adequate calcium intake will lay the foundation for bone health,” said lead author Dr. Rebecca Jackson at Ohio State University.
Dr. Bess Dawson-Hughes, a Tufts University vitamin expert who helped shape the dietary guidelines, said they should remain unchanged for now. She largely dismissed the overall negative finding.
“You put people who don’t need it together with people who aren’t taking it, and you find nothing – and that really isn’t all that surprising,” she said.
Some researchers said the effect would have been clearer with higher doses of vitamin D.
“We don’t want to send the message to people to throw away their calcium pills, which was my wife’s first reaction,” said Lasser, a study author.
