Neither one guards against cancer or serious heart problems
by Liz Szabo /
Kaiser Health News | November 12, 2018
A widely anticipated study has concluded that
neither vitamin D nor fish oil supplements prevent cancer or serious
heart-related problems in healthy older people, according to research presented
Saturday at the American Heart Association Scientific Sessions. Researchers
defined serious heart problems as the combined rate of heart attacks, stroke
and heart-related deaths.
Although hundreds of
studies of these supplements have been published over the years, the new
clinical trial—a federally funded project involving nearly 26,000 people—is the
strongest and most definitive examination yet, said Dr. Clifford Rosen, a
senior scientist at the Maine Medical Center Research Institute who was not
involved in the research.
The new study also
suggests there’s no reason for people to undergo routine blood tests for
vitamin D, said Rosen, who co-wrote an accompanying editorial. (Both were
published in the New England Journal of Medicine.) That’s because the study
found that patients’ vitamin D levels made no difference in their risk of
cancer or serious heart issues, Rosen said.
Even people who began
the study with clear vitamin D deficiency got no benefit from taking the
supplements, which provided 2,000 international units a day. This amount is
equal to one or two of the vitamin D pills typically sold in stores.
Doctors have been
keenly interested in learning the supplements’ true value, given their
tremendous popularity with patients. A 2017 study
found that 26% of Americans age 60 and older take vitamin D supplements, while
22% take pills containing omega-3 fatty acids, a key ingredient in fish oil.
Time to stop vitamin
D tests
A recent Kaiser
Health News story reported that vitamin D testing has become a huge business
for commercial labs—and an enormous expense for taxpayers. Doctors ordered more
than 10 million
vitamin D tests for Medicare patients in 2016—an increase of 547%
since 2007 —at a cost of $365 million.
“It’s time to stop
it,” said Rosen of vitamin D testing. “There’s no justification.”
Dr. JoAnn Manson, the
study’s lead author, agrees that her results don’t support screening healthy
people for vitamin D deficiency.
But she doesn’t see her
study as entirely negative.
Manson notes that her
team found no serious side effects from taking either fish oil or vitamin D
supplements.
“If you’re already
taking fish oil or vitamin D, our results would not provide a clear reason to
stop,” Manson said.
Manson notes that a
deeper look into the data suggested possible benefits.
Disagreement on
benefits
When researchers
singled out heart attacks—rather than the rate of all serious heart problems
combined—they saw that fish oil appeared to reduce heart attacks by 28%, Manson
said. As for vitamin D, it appeared to reduce cancer deaths—although not cancer
diagnoses—by 25%.
But slicing the data
into smaller segments—with fewer patients in each group—can produce unreliable
results, said Dr. Barnett Kramer, director of the cancer prevention division at
the National Cancer Institute. The links between fish oil and heart attacks—and
vitamin D and cancer death—could be due to chance, Kramer said.
Experts agree that
vitamin D is important for bone health. Researchers didn’t report on its effect
on bones in these papers, however. Instead, they looked at areas where vitamin
D’s benefits haven’t been definitely proven, such as cancer and heart disease.
Although preliminary studies have suggested vitamin D can prevent heart disease
and cancer, more rigorous studies have disputed those findings.
Manson and her
colleagues plan to publish data on the supplements’ effects on other areas of
health in coming months, including diabetes, memory and mental functioning,
autoimmune disease, respiratory infections and depression.
Consumers who want to
reduce their risk of cancer and heart disease can follow other proven strategies.
“People should
continue to focus on known factors to reduce cancer and heart disease: Eat
right, exercise, don’t smoke, control high blood pressure, take a statin if you
are high risk,” said Dr. Alex Krist, a professor of family medicine and population
health at Virginia Commonwealth University.
Kaiser Health News
(KHN) is a national health policy news service. It is an editorially
independent program of the Henry J. Kaiser
Family Foundation which is not affiliated with Kaiser
Permanente.
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