​Vitamin D Supplements: Risk For Low Dose

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June 16, 2012

The United States Preventive Services Task Force is recommending that healthy postmenopausal women should not take low doses of calcium or vitamin D supplements.

The group, an independent panel of experts in prevention and primary care appointed by the federal Department of Health and Human Services, also considered use of the supplements by healthy premenopausal women and men. For those groups, it said, there was insufficient evidence to recommend taking vitamin D with or without calcium to prevent fractures.

The supplements also have been studied to see if they prevent cancer. But, the group said, there is insufficient evidence to say they do or do not. The cancer studies included ones testing the supplements to prevent all cancers as well as ones asking about colorectal cancer, prostate cancer and breast cancer.

Their analysis of the effects of the supplements included 137 studies, including randomized controlled trials, the gold standard for clinical evidence.

The low doses that the group referred to, at least for the postmenopausal women, were a typical level of 400 international units or less of vitamin D a day and 1,000 milligrams or less of calcium.

At that dose, said Dr. Kirsten Bibbins-Domingo, a member of the task force who is an associate professor of medicine at the University of California in San Francisco, “there is sufficient evidence to say they do not prevent fractures.”

“When you take a vitamin supplement or any therapy for an extended period of time, you have to ask, ‘What is the evidence that it works and what is the evidence of harms?’ ” Dr. Bibbins-Domingo said.

“It is clear that lower doses of calcium and vitamin D do not prevent fractures, and there is a small but measurable risk of kidney stones,” she said. So with no evidence of benefit, there is no reason to risk harm.

Dr. Ethel Siris, who directs Columbia University’s osteoporosis center, said she and other osteoporosis experts already knew the supplements did not prevent fractures.

“That’s why when a patient with osteoporosis says, ‘I will just take calcium and vitamin D,’ we say, ‘That’s not enough,’ ” Dr. Siris said.

But Dr. Bibbins-Domingo said the task force recommendations did not apply to people with osteoporosis.

For most people, she said, there is no need for these supplements and good reason for many not to take them.

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