TUESDAY, May 10, 2005 (HealthDay News) -- Vitamin D supplements can prevent fractures in elderly people, according to new research that comes hard on the heels of two British studies that found just the opposite.
This latest research is a major review of data from clinical trials that met rigid standards for quality, said Dr. Heike A. Bischoff-Ferrari, an instructor in the Harvard Medical School department of medicine. She is lead author of the report, which appears in the May 11 issue of the Journal of the American Medical Association.
One of the two studies that came to the opposite conclusion, published on April 30 in the British Medical Journal, "would not have met our quality standards," she said, for several reasons. For example, the study of 3,314 women aged 70 and older was not double-blind, meaning those in the control group knew they were in a study and might have increased their vitamin D intake even though they were not supposed to do so.
And the results of the other study, of 5,292 older people hospitalized with fractures, might be doubtful because it was done in a population at especially high risk -- older people who already had suffered fractures and people who did not take vitamin D doses high enough to overcome initially low levels, she said.
That study, reported in the April 27 issue of The Lancet, did meet the standards, Bischoff-Ferrari said, but her interpretation of the results actually supports the use of vitamin D supplements to prevent fractures, she said.
At any rate, both of those studies were published too late to be included in the new report, and would not have changed the conclusion that vitamin D supplements are beneficial, Bischoff-Ferrari said.
Dr. Adrian Grant, director of the health services research unit at the University of Aberdeen in Scotland, who led the Lancet study, begged to differ.
Just as Bischoff-Ferrari picked holes in his study, he found flaws in hers. The Scottish trial was designed to find out whether the combination of vitamin D and calcium supplements affected the risk of fracture, Grant said, while the new study "tried to disentangle the effects of calcium in addition to vitamin D."
"They make a distinction between high-dose and low-dose vitamin D supplementation, and high-dose supplementation generally included calcium," he said.
In addition, "their finding is very heavily dependent on two trials conducted in France on frail, elderly institutionalized individuals," Grant said. "If you take those two trials out, the evidence really becomes much weaker." And "they excluded many trials of vitamin D that other reviewers might have included," he said.
That fact that the report is published in a medical journal, rather than in electronic form, also drew his criticism. "Paper-based reviews are out of date by the time they are published," Grant said.
Grant said he did not feel that he could make recommendations about the use of vitamin D supplements to prevent the fractures that affect so many elderly people.
Bischoff-Ferrari said she was quite ready to make a recommendation, in view of the high incidence of fractures in elderly Americans. One of every three women and one of every six men who live to be 90 will sustain a hip fracture, her report said, with 10 percent to 20 percent of them dying within a year and 15 percent to 25 percent requiring long-term nursing home care.
"If someone did not have a fracture yet, I would recommend 700 to 800 International Units (IU) of vitamin D a day, with at least 700 milligrams of calcium," she said. "If you have had a fracture, you should discuss with your physician whether you may need more. The National Science Foundation says the safe upper limit is 2,000 units a day, so you can go to 1,500 units or higher, especially if you live in a country like the United Kingdom, where you have little exposure to sunlight." Sunlight enhances the body's production of vitamin D.
More information
Osteoporosis, the age-related condition that increases the risk of fractures, is explained by the National Institutes of Health.
