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TORONTO, Thu. Apr. 28 2005
Grant, a health services researcher
at the University of Aberdeen in Scotland, suggested people
taking - or advising people to
take - the supplements should reserve judgment for the time
being. "There are a number of quite large trials that will
be reporting in the next few months. And I think the right
thing to do is to wait and see what those results are," he
said.
The findings appear to be at odds with earlier studies
showing calcium and vitamin D help prevent older people from
suffering a first bone fracture. Experts fear the interpretation
of the findings will lead seniors to wonder whether they ought
to toss, not take, their supplements. "All the public is going
to get out of it is confusion," said Reinhold Vieth, a leading
vitamin D expert who works in the pathology department at Toronto's
Mount Sinai Hospital.
"That's going to set things back about
10 years," said Dr. Cy Frank, scientific director of the Canadian
Institutes of Health Research's Institute of Musculoskeletal
Health and Arthritis. "I'm not pushing the idea as a zealot,
that everybody should be taking calcium supplements and all
of the pharmaceutical approach. . . . (But) over-generalizing
(the results) could be harmful to a lot of people, until it's
proven that it doesn't matter . . . in any population."
The
medical director of the osteoporosis program at Toronto's Sunnybrook
and Women's College Health Sciences Centre looked at the results
through a different prism, saying they don't prove there is
no role for the supplements, but rather that vitamin D and
calcium aren't sufficient to treat older people who are starting
to suffer bone fractures.
"These studies don't say that there's
no benefit to calcium and vitamin D," Dr. Gillian Hawker said,
insisting there is still a role for the supplements in conjunction
with drugs such as bisphosphonates which are used to combat
bone loss caused by osteoporosis.
"What they say is that in
people who are at very high risk of another fracture and are
unlikely to have vitamin D or calcium deficiency . . . it's
not enough to just give calcium and vitamin D and figure you're
having a benefit on fracture risk."
The Record trial looked
at 5,292 people across Britain aged 70 and older who were mobile
and living in their own homes - an important feature because
residents of nursing homes are generally less physically active
and more likely to suffer vitamin D deficiency.
In order to
qualify for the study, subjects had to have already suffered
a fracture.
They were randomly divided into four groups, receiving
either 800 international units of vitamin D daily, 1,000 milligrams
of calcium, calcium and vitamin D combined or placebo pills.
Participants were followed over two to five years to see whether
people getting the supplements had fewer new bone breaks. But
there was no real difference in fracture rates between the
four branches of the study.
The second trial, published in
the British Medical Journal, looked at 3,314 British women
aged 70 and older with one or more risk factor for suffering
a hip fracture.
They were randomized to receive either 1,000
milligrams of calcium and 800 units of vitamin D a day or no
supplements. They were followed for 18 to 42 months to see
if one or the other group had higher rates of hip fractures.
The researchers, from the University of York, found no statistically
significant difference between the two groups.
Both research
groups noted, however, that compliance rates - in other words,
the percentage of people who took the treatment they were told
to take - was low, hovering around 60 per cent or even lower.
That could have had an impact on the findings, both they and
external experts critiquing the studies suggested.
Critics
identified other limitations.
Vieth, for instance, suggested
the dose of vitamin D used in both studies may have been too
low. And Dr. Philip Sambrook, of the Institute of Bone and
Joint Research at the University of Sydney, Australia, noted
the study in Lancet only tested a small fraction of participants
at the start to see if they were suffering from a vitamin D
deficiency.
"Until we have a 'negative' study in a population
who is definitely vitamin D deficient, it would be wrong to
not treat vitamin D deficient people," Sambrook, who wrote
a commentary for the journal, said in an e-mail interview.
"From
this study we just don't know enough about their vitamin D
status to disregard the previous data."
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