Can vitamin D, fish oil prevent cancer, heart disease?
Study to target blacks in particular
Monday, June 22, 2009
Two of the most popular and promising dietary supplements - vitamin D and
fish oil - will be tested in a large, government-sponsored study to see
whether either nutrient can lower a healthy person's risk of getting cancer,
heart disease or having a stroke.
It will be one of the first big nutrition studies ever to target a specific
racial group - blacks, who will comprise one quarter of the participants.
People with dark skin are unable to make much vitamin D from sunlight, and
researchers think this deficiency may help explain why blacks have higher
rates of cancer, stroke and heart disease.
"If something as simple as taking a vitamin D pill could help lower these
risks and eliminate these health disparities, that would be extraordinarily
exciting," said Dr. JoAnn Manson.
She and Dr. Julie Buring, of Harvard-affiliated Brigham and Women's Hospital
in Boston, will co-lead the study.
"But we should be cautious before jumping on the bandwagon to take
mega-doses of these supplements," Manson warned. "We know from history that
many of these nutrients that looked promising in observational studies
didn't pan out."
Vitamins C, E,
folic acid, beta carotene, selenium and even menopause
hormone pills once seemed to lower the risk of cancer or heart disease _
until they were tested in big studies that sometimes revealed risks instead
of benefits.
In October, the government stopped a big study of
vitamin E and selenium
pills for prostate cancer prevention after seeing no evidence of benefit and
hints of harm.
Vitamin D is one of the last major nutrients to be put to a rigorous test.
For years, evidence has been building that many people are deficient in "the
sunshine vitamin." It is tough to get enough from dietary sources like milk
and oily fish. Cancer rates are higher in many northern regions where
sunlight is weak in the winter, and some studies have found that people with
lower blood levels of vitamin D are more likely to develop cancer.
Fish oil, or omega-3 fatty acid, is widely recommended for heart health.
However, studies of it so far have mostly involved people who already have
heart problems or who eat a lot of fish, such as in Japan. Foods also
increasingly are fortified with omega-3, so it is important to establish its
safety and benefit.
"Vitamin D and omega-3s have powerful anti-inflammatory effects that may be
key factors in preventing many diseases. They may also work through other
pathways that influence cancer and cardiovascular risk," Manson said.
However, getting nutrients from a pill is different than getting them from
foods, and correcting a deficiency is not the same as healthy people taking
large doses from a supplement.
The new study, which will start later this year, will enroll 20,000 people
with no history of heart attacks, stroke or a major cancer - women 65 or
older and men 60 or older.
They will be randomly assigned to take vitamin D, fish oil, both nutrients
or dummy pills for five years.
The daily dose of vitamin D will be about 2,000 international units of D-3,
also known as cholecalciferol, the most active form.
For fish oil, the daily dose will be about one gram - five to 10 times what
the average American gets.
Participants' health will be monitored through questionnaires, medical
records and in some cases, periodic in-person exams.
"We're hoping to see a result during the trial, that we won't have to wait
five years" to find out if supplements help, Manson said.
Researchers also plan to study whether these nutrients help prevent memory
loss, depression, diabetes, osteoporosis and other problems, Buring said.
The $20 million study will be sponsored by the National Cancer Institute,
with the National Heart, Lung and Blood Institute and other federal
agencies.
Pharmavite LLC of Northridge, Calif., is providing the vitamin D pills, and
Ocean Nutrition Canada Ltd. of Dartmouth, Nova Scotia, is providing the
omega-3 fish oil capsules.
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On the Net:
Study information:
http://www.vitalstudy.org
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