[PHNUTR-L] WCO: Meta-Analysis Defends Bone Benefit for Vitamin D
Kathrynne Holden, MS, RD
fivestar at nutritionucanlivewith.com
Thu Jun 8 05:14:52 PDT 2006
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WCO: Meta-Analysis Defends Bone Benefit for Vitamin D with Calcium
By Michael Smith, MedPage Today Staff Writer
Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of
Pennsylvania School of Medicine.
June 06, 2006
MedPage Today Action Points
* Advise patients who ask that two recent studies seemed to show
that combined supplements of calcium and Vitamin D had little effect on
the risk of osteoporotic fractures.
* Note that this study—a meta-analysis of randomized
placebo-controlled studies—comes to the opposite conclusion.
* This study was published as an abstract and presented orally at a
conference. These data and conclusions should be considered to be
preliminary as they have not yet been reviewed and published in a
Steven Boonen, M.D., Ph.D., Leuven University
TORONTO, June 6 — The concept of calcium and vitamin D supplementation
for prevention of osteoporosis, relegated recently to the realm of
unfounded notion, got a spirited defense here.
The combination is "very effective, but you have to give it to the right
people and in the right dose," Steven Boonen, M.D., Ph.D., of Leuven
University in Belgium said at the World Congress on Osteoporosis here.
Dr. Boonen presented results of a meta-analysis of major randomized
placebo-controlled trials that analyzed the effects of vitamin D alone
or in combination with calcium. The meta-analysis found that in patients
getting 800 units of vitamin D and more than 1,000 mg of calcium a day,
there was a 21% reduction in risk of fracture compared to placebo.
The meta-analysis included the RECORD study, published last year in The
Lancet, and data from the Women's Health Initiative, published earlier
this year in the New England Journal of Medicine. Both the latter
studies found no benefit to adding calcium to vitamin D to prevent
fractures in menopausal women.
But Dr. Boonen said their methods were flawed, leading to an incorrect
For one thing, he said, neither study had enough statistical power to
find an effect. For instance, he said, the RECORD trial, looking at hip
fractures, had 2,649 participants and only 93 events. By contrast, Dr.
Boonen said, he and his colleagues had a patient pool of 16,978
individuals and 812 fractures.
Also, he said, both studies were community-based, meaning that many of
their participants were actually getting enough calcium and vitamin D
without taking supplements. By including such healthy women, he said,
"you dilute the treatment effect."
"It doesn't make sense to give calcium and vitamin D if there's no
insufficiency," he said.
And finally, he noted, in both trials, compliance was on the order of
40% and 50%. When the researchers analyzed those who actually took their
supplements, he said, "they did see an effect."
Dr. Boonen and colleagues actually presented two analyses. In one, they
looked at randomized clinical trials comparing vitamin D alone to
placebo and found no effect. The odds ratio was actually slightly in
favor of placebo at 1.10, but the 95% confidence interval ranged from
0.89 to 1.36.
On the other hand, they found that when combined with calcium vitamin D
had a significant benefit in reducing fracture. The odds ratio was 0.79,
with a 95% confidence interval from 0.64 to 0.97. The number needed to
treat to prevent one fracture was 132.
A subsidiary analysis showed that low doses of vitamin D—below 800 units
a day—had no effect, he said.
For clinicians, "the point of (the study) is that you should always give
both," said endocrinologist B. Lawrence Riggs, M.D., of the Mayo Clinic
in Rochester, Minn., who chaired the session in which Dr. Boonen's
research was presented.
"Some people believe that vitamin D is enough but vitamin D exerts its
effect on bone predominantly by increasing absorption of calcium," Dr.
Riggs said in an interview. "If you don't have enough calcium, it's not
Dr. Boonen told reporters after his presentation that clinicians need to
pay attention to four factors. They must prescribe a combination of
calcium and vitamin D, the doses must be high enough, the patients must
be in need of the supplements, and finally they must actually take their
Primary source: Osteoporosis International
Boonen S et al. "Fracture Risk Reduction With Vitamin D Supplementation
Requires Additional Calcium: Evidence From A Comparative Meta-Analysis."
Osteoporos Int 2006; 17 (Suppl 2): 13.
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
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