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Older Women Study Results
Calcium, Vitamin D Supplements Offer Modest Bone Improvements, No
Benefits for Colorectal Cancer
Feb. 16, 2006 - Calcium and vitamin D supplements
in healthy postmenopausal women provide a modest benefit in preserving
bone mass and prevent hip fractures in certain groups including older
women but do not prevent other types of fractures or colorectal cancer,
according to the results of a major clinical trial, part of the Women’s
Health Initiative (WHI).
While generally well tolerated, the supplements
were associated with an increased risk of kidney stones.
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The study results are published in today's issue
of The New England Journal of Medicine. The WHI is sponsored by the
National Heart, Lung, and Blood Institute (NHLBI) of the National
Institutes of Health.
“This important study provides guidance for women
on the risks and benefits of supplementing their diets with calcium and
vitamin D. The overall results suggest that women, particularly those
over 60, should consider taking calcium and vitamin D for bone health
but they should not expect these supplements to help prevent colorectal
cancer,” said Elizabeth G. Nabel, M.D., NHLBI director and director of
the Women’s Health Initiative.
The WHI Calcium with Vitamin D (CaD) trial of
36,282 postmenopausal women ages 50 to 79 found a small but significant
1 percent higher hip bone density for those taking calcium combined with
vitamin D compared to those taking placebo. During the trial, 374 women
had hip fractures with a fracture rate of 14 per 10,000 cases per year
in the supplemented group compared to 16 per 10,000 per year in the
placebo group. This 12 percent reduction in hip fracture in those taking
the calcium plus vitamin D supplement was not statistically significant;
however, women who consistently took the full supplement dose
experienced a significant 29 percent decrease in hip fracture. Women
older than 60 had a significant 21 percent reduction in hip fracture.
The supplements had no significant effect on spine or total fractures.
Calcium/vitamin D supplements provided no
detectable effect on the incidence of colorectal cancer. There were
similar rates of cancer in both the calcium/vitamin D and placebo groups
(13 cases per 10,000/year compared to 12 cases per 10,000/year
respectively).
Overall, the supplements were well tolerated by
participants and the only adverse effect found was a 17 percent increase
in kidney stones. Kidney stones were reported by 449 women (34 cases per
10,000 per year) in the CaD group compared to 381 women (29 cases per
10,000 per year) in the placebo group.
The WHI Calcium with Vitamin D trial was primarily
designed to study the effect of calcium/vitamin D supplementation on
preventing hip fracture with secondary study objectives testing the
effect of CaD on spine and other types of fracture and on colorectal
cancer. Participants in this study had previously enrolled in one or
both of the WHI trials of hormone therapy or dietary modification.
Half of the over 36,000 participants in the CaD
trial received a daily dose of 1000 milligrams of calcium carbonate
combined with 400 IUs of vitamin D3. The other half of the study group
received placebo pills in similarly marked bottles. Participants could
choose between chewable or swallowable pills. During the study, a
sub-set of participants had regular bone density scans. Study
participants were followed for an average of 7 years with three-quarters
of them still taking their pills by the end of the study.
Osteoporosis, a skeletal disorder characterized by
weakened bones leading to an increased risk of fracture is a major cause
of disability, loss of independence, and death. It contributes to an
estimated 300,000 hip fractures in the U.S. each year. Four out of 10
women over 50 will experience a fracture at the hip, spine, or wrist in
their lifetime. Ten million people in the U.S. are estimated to have
osteoporosis and 34 million more have low bone mass, placing them at
greater risk for fracture.
“Given the serious public health burden of
fractures associated with osteoporosis, it is important to learn as much
as possible about ways to prevent and treat bone loss,” said Joan
McGowan, Ph.D., of the NIH’s National Institute of Arthritis and
Musculoskeletal and Skin Diseases (NIAMS) and a co-author on the paper.
According to the study’s authors, there are several
possible reasons why despite improvements in hip bone density, the
reduction in hip fractures was smaller than expected and only
statistically significant in certain groups — those over 60 and women
who took the full intended dose of combined supplements.
”Although 76 percent of women were still taking
study pills at the end of the trial, only 59 percent were taking the
intended number of pills,” said Rebecca D. Jackson, M.D.,
endocrinologist and the study’s lead investigator at Ohio State
University in Columbus. “In a secondary analysis, we found a significant
29 percent decrease in hip fracture risk among women who took most of
their study pills — that’s four fewer hip fractures for every 10,000
women per year,” she said.
The rate of hip fractures was about half of what
was expected, and this decreased study power to show a significant
finding, according to Dr. Jackson. "The low rates could be due to a
number of factors, such as the high body mass index of participants
(heavier people have stronger bones), the inclusion of relatively few
women over age 70 years, and the fact that many participants were
already using calcium and vitamin D supplements, or were on hormone
therapy," she said.
“If we look at all the findings together,” said
McGowan, “for every 10,000 women treated for one year, two hip fractures
would be prevented and five cases of kidney stones would be caused. The
number of hip fractures prevented would climb to four for compliant
patients and six for women over 60. Since hip fractures are considered
to be more serious than kidney stones, on balance, the public health
benefit of the supplements outweighs the risks.”
“The study’s findings of slowed bone loss and the
reduction in hip fractures for some groups suggest a role for these
supplements in preventing hip fracture in generally healthy
postmenopausal women and support the current Surgeon General’s
recommendations for these nutrients,” added McGowan, who is also the
senior scientific editor of the Surgeon General’s report on bone health.
She noted, however, that supplements may not be necessary for healthy
women whose diet meets recommended levels of calcium and vitamin D.
The study found no evidence of benefit from
calcium/vitamin D for the prevention of colorectal cancer, according to
Jean Wactawski-Wende, Ph.D., epidemiologist and the study’s lead
investigator at the University at Buffalo.
Over an average of 7 years, 322 women in the study
were diagnosed with invasive colorectal cancer. There was no
statistically significant difference between the two groups in number of
cancer cases or in the characteristics or severity of tumors. There were
also no differences between groups in the number of polyps reported by
the participants. When the investigators analyzed only the data obtained
from participants who were taking most of their study pills, there was
still no benefit seen from calcium/vitamin D supplementation.
“As the third leading cause of cancer death and
incidence for women in the United States, there is great interest in the
prevention of colorectal cancer. Unfortunately, our findings do not
validate some previous studies and polyp prevention trials which showed
a benefit for calcium/vitamin D,” said Wactawski-Wende.
She added, however, that study design and
population issues may have limited the study’s ability to show a
protective effect of calcium/vitamin D. Since participants were not
restricted from taking personal calcium or vitamin D supplements, they
had a relatively high calcium and vitamin D intake at enrollment and
intake rose even higher during the trial so the impact of study
supplementation may have been muted.
Duration may have also been a factor, said
Wactawski-Wende. “If the benefit of CaD is for prevention of cancer at
its early stages and colorectal cancer takes 10 to 20 years to develop,
7 years of supplementation and follow-up may not be enough time to show
a benefit. Still, we found no trend toward protection in the later years
of follow-up,” she said. She added that the ongoing 5-year WHI extension
study will continue to track occurrences of colorectal cancer — as well
as other diseases — and may provide answers on later effects of the WHI
CaD supplementation.
“The WHI will continue to provide us with answers
about the major health conditions affecting women for years to come,”
said Nabel, “The study’s participants and investigators have made major
contributions to disease prevention in postmenopausal women.”
Additional Resources:
● For a summary of health recommendations for
postmenopausal women based on the WHI results and other studies, see
http://www.nhlbi.nih.gov/whi/recommend.htm.
● For information on bone health and
osteoporosis, see
www.niams.nih.gov and
http://www.niapublications.org/agepages/osteo.asp.
● For information on eating for general health,
see
www.health.gov/dietaryguidelines/dga2005/recommendations.htm.
● For information on dietary supplements, see
http://dietary-supplements.info.nih.gov/index.aspx.
● For more on the Women's Health Initiative, see
http://www.nhlbi.nih.gov/whi/.
WHI — a Legacy to Future Generations, a conference
on the past, present, and future of WHI (including synthesis of findings
generated from the WHI observational study and all four clinical trials
— estrogen plus progestin, estrogen alone, dietary modification, and
calcium/vitamin D — will be held February 28-March 1, 2006 on the NIH
campus. For more information and a conference agenda, go to:
http://www.nhlbi.nih.gov/whi/references.htm.
NHLBI, NIAMS, and NCI are part of the National
Institutes of Health (NIH), the Federal Government’s primary agency for
biomedical and behavioral research. NIH is a component of the U.S.
Department of Health and Human Services. For more information, go to:
www.nhlbi.nih.gov,
www.niams.nih.gov,
www.nci.nih.gov.
The National Institutes of Health (NIH) — The
Nation's Medical Research Agency — includes 27 Institutes and Centers
and is a component of the U. S. Department of Health and Human Services.
It is the primary Federal agency for conducting and supporting basic,
clinical, and translational medical research, and it investigates the
causes, treatments, and cures for both common and rare diseases. For
more information about NIH and its programs, visit
http://www.nih.gov.
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