Special Interest Articles
Vitamin D Appears to Cut Breast and Colorectal Cancer
Risk News Author:
Allison Gandey Release Date: February 12, 2007
February 12, 2007 - Researchers say that raising vitamin
D levels may
prevent up to half of all breast and two thirds of
colorectal cancer cases
in the United States. Based on the results of 2 separate
studies, the
investigators recommend a daily intake of 2000 IU of
vitamin D3 and, when
possible, moderate sun exposure.
"The results are pretty straightforward," Karen Glanz,
PhD, director of
Emory University's Prevention Research Center at the
Rollins School of
Public Health in Atlanta, Georgia, said in a news
release. However, changing
behavior on the basis of these studies may be premature,
she noted. The
analyses found an association between vitamin D levels
and lowered risk, not
a definite link, Dr. Glanz said, but adding vitamin D to
the diet or taking
a supplement would probably not do much harm and there
could be a benefit.
During an interview with Medscape, lead author Cedric
Garland, DrPH, of the
University of California at San Diego, agreed that
future consensus is
needed, but he recommended no delay in raising vitamin D
levels. "We
shouldn't hold up implementation," he said. "Inadequate
photosynthesis or
oral intake of vitamin D is associated with high
incidence and mortality
rates of breast cancer."
Published in the January 30 Article in Press issue of
the Journal of Steroid
Biochemistry and Molecular Biology, the researchers
pooled dose-response
data from 2 previous studies - the Harvard Nurses Health
Study and the St.
George's Hospital Study. They found that patients with
the highest blood
levels of 25-hydroxyvitamin D had the lowest risk for
breast cancer.
Dr. Garland and his team divided the more than 1700
records in the studies
into 5 groups from the lowest blood levels of
25-hydroxyvitamin D (< 13
ng/mL) to the highest (approximately 52 ng/mL). These
data also included
whether the patient had developed cancer.
The investigators found that patients with serum
25-hydroxyvitamin D of
approximately 52 ng/mL had a 50% lower risk for breast
cancer than those
with serum measuring less than 13 ng/mL. This level
corresponds to a vitamin
D intake of 4000 IU per day, which exceeds the National
Academy of Sciences
upper limit of 2000 IU per day. "Leading researchers are
building a case to
have this level increased," Dr. Garland told Medscape,
"but in the meantime,
we are recommending a daily intake of 2000 IU."
The group is also calling for an additional 10 to 15
minutes of daily sun
exposure when appropriate - an amount estimated to be
equivalent to an oral
intake of 3000 IU of vitamin D3.
But What About the Risk for Skin Cancer?
As previously reported by Medscape, the American Academy
of Dermatology has
voiced concern about the vitamin D literature
prescribing the health
benefits of sunlight. "While many health issues are
complex and involve
multiple factors, we know that ultraviolet light is the
primary cause of
skin cancer, and avoiding excessive exposure to the sun
and other forms of
ultraviolet radiation is the solution," Clay Cockerell,
MD, president of the
academy said in a news release.
During an interview with Medscape, Dr. Garland
emphasized that his group is
advocating prudence and moderation, including the use of
a broad-brimmed
hat. "I think most physicians will see this as a
well-controlled and
reasonable approach," he added.
The article points out that sun exposure is inadvisable
for patients with
primary photosensitivity disorders, people taking
photosensitizing
medications, and anyone with a personal or close family
history of skin
cancer or actinic keratosis.
Evidence Stacking in Favor of Vitamin D
Dr. Garland was also a coauthor of a second study
examining the effect of
vitamin D levels on colon cancer risk. Published in the
February issue of
the American Journal of Preventive Medicine, the
researchers conducted a
meta-analysis of 5 studies examining serum
25-hydroxyvitamin in colorectal
cancer.
The investigators combined the findings of the 5 studies
using standard
methods for pooled analysis. There were 535 cases and
913 controls or 1448
participants in total. The researchers divided the
results into quintiles
with median 25-hydroxyvitamin values of 6, 16, 22, 27,
and 37 ng/mL.
Previous studies had shown that lower blood levels of
vitamin D did not
protect against colorectal cancer, but in the current
study, the researchers
came to a different conclusion. "Through this
meta-analysis we found that
raising the serum level of 25-hydroxyvitamin D to 34 ng/mL
would reduce the
incidence rates of colorectal cancer by half," lead
author Edward Gorham,
MPH, PhD, a research epidemiologist with the Naval
Health Research Center in
San Diego told reporters. "We project a two-thirds
reduction in incidence
with serum levels of 46 ng/mL."
The amount of dietary vitamin D needed to reach the
serum levels that appear
to be protective against colorectal cancer - 1000 to
2000 IU per day - would
not pose any risk, Dr. Gorham said. "The Institute of
Medicine has set a 'No
Adverse Effect Level' of 2000 IU per day for vitamin D
intake, so this
recommendation would be safe for most people."
J Steroid Biochem Mol Biol. Published online January 30,
2007.
Am J Prev Med. 2007;32:210-216.
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Impac Health is for informational purposes only and is not a
substitute for seeking clinical advice or treatment
relating to any medical condition. If you have a concern
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