High Level of Omega-3 in Blood of Older Men Hikes
Risk of Aggressive Prostate Cancer
Study leader says beneficial effects of eating fish
to prevent heart disease still outweigh any harm related to prostate
cancer risk
April 25, 2011 – It appears
too much of a good thing can equal trouble. A new nationwide study finds
that older men with the highest levels of omega-3 fatty acid – that
highly recommended supplement gulped my millions of senior citizens
seeking better health – are much more likely to develop aggressive,
high-grade prostate cancer.
Billed as the largest study
ever to examine the association of dietary fats and prostate cancer
risk, the data of 3,400 men gathered by researchers at Fred Hutchinson
Cancer Research Center has revealed what's good for the heart may not be
good for the prostate.
Actually, it appears to
increase the risk for men with the highest blood percentages of
docosahexaenoic acid, or DHA, by two-and-a-half-times compared to men
with the lowest DHA levels.
Women who ate the
most fish did the best at reducing the risk of this leading cause of
blindness in senior citizens - March
15, 2011 (Note see more about Omega-3 fighting AMD below news story.)
Study finds eating fatty fish once a week reduces
heart failure risk, eating more does not. Omega-3 fatty acid benefits
confirmed, too – if taken in the right amounts
Conversely, the study also
found that men with the highest blood ratios of trans-fatty acids –
which are linked to inflammation and heart disease and abundant in
processed foods that contain partially hydrogenated vegetable oils – had
a 50 percent reduction in the risk of high-grade prostate cancer.
In addition, neither of these
fats was associated with the risk of low-grade prostate cancer risk. The
researchers also found that omega-6 fatty acids, which are found in most
vegetable oils and are linked to inflammation and heart disease, were
not associated with prostate cancer risk. They also found that none of
the fats were associated with the risk of low-grade prostate cancer.
"We were stunned to see these
results and we spent a lot of time making sure the analyses were
correct," said Theodore M. Brasky, Ph.D., a postdoctoral research fellow
in the Hutchinson Center's Cancer Prevention Program.
"Our findings turn what we
know – or rather what we think we know – about diet, inflammation and
the development of prostate cancer on its head and shine a light on the
complexity of studying the association between nutrition and the risk of
various chronic diseases."
The researchers undertook the
study because chronic inflammation is known to increase the risk of
several cancers, and the omega-3 fatty acids found primarily in fish and
fish oil supplements have anti-inflammatory effects.
In contrast, other fats, such
as the omega-6 fats in vegetable oil and trans-fats found in fast foods,
may promote inflammation.
"We wanted to test the
hypothesis that the concentrations of these fats in blood would be
associated with prostate cancer risk," Brasky said.
"Specifically, we thought that
omega-3 fatty acids would reduce and omega-6 and trans-fatty acids would
increase prostate cancer risk."
The mechanisms behind the
impact of omega-3s on risk of high-grade prostate cancer are unknown.
"Besides inflammation, omega-3 fats affect other biologic processes. It
may be that these mechanisms play a greater role in the development of
certain prostate cancers," Brasky said. "This is certainly an area that
needs more research."
Currently there is no official
recommended daily allowance for omega-3 fats for adults or children,
although many nutrition experts and physicians recommend 450 milligrams
of omega-3 DHA per day as part of a healthy diet.
The study was based on data
from the Prostate Cancer Prevention Trial, a nationwide randomized
clinical trial that tested the efficacy of the drug finasteride to
prevent prostate cancer.
While the trial involved
nearly 19,000 men age 55 and older, the data in this analysis came from
a subset of more than 3,000 of the study participants, half of whom
developed prostate cancer during the course of the study and half of
whom did not. The clinical trial was unique in that prostate biopsy was
used to confirm the presence or absence of prostate cancer in all study
participants.
Among the study participants,
very few took fish oil supplements – the most common non-food source of
omega-3 fatty acids, which are known to prevent heart disease and other
inflammatory conditions. The majority got omega 3s from eating fish.
So based on these findings,
should men concerned about heart disease eschew fish oil supplements or
grilled salmon in the interest of reducing their risk of aggressive
prostate cancer? Brasky and colleagues don't think so.
"Overall, the beneficial
effects of eating fish to prevent heart disease outweigh any harm
related to prostate cancer risk," Brasky said.
"What this study shows is the
complexity of nutrition and its impact on disease risk, and that we
should study such associations rigorously rather than make assumptions,"
Brasky said.
These findings by Brasky and
colleagues in the Hutchinson Center's Public Health Sciences Division
were published online today, April 25, in the American Journal of
Epidemiology.
The National Cancer Institute
funded this study, which also involved researchers from the University
of Texas Health Science Center at San Antonio and the NCI.
At Fred Hutchinson Cancer
Research Center, our interdisciplinary teams of world-renowned
scientists and humanitarians work together to prevent, diagnose and
treat cancer, HIV/AIDS and other diseases. Our researchers, including
three Nobel laureates, bring a relentless pursuit and passion for
health, knowledge and hope to their work and to the world.
www.fhcrc.org
A number of studies have linked Omega-3 with reducing the risk of
AMD
April 25, 2011 – It appears
too much of a good thing can equal trouble. A new nationwide study finds
that older men with the highest levels of omega-3 fatty acid – that
highly recommended supplement gulped my millions of senior citizens
seeking better health – are much more likely to develop aggressive,
high-grade prostate cancer.