Omega 3s, Prostate Cancer, and Atrial Fibrillation


“Omega 3’s, Prostate Cancer,
and Atrial Fibrillation” 2013 was a bad year for fish oil. Claims were crushed that
the long chain omega 3’s in fish oil, EPA, and DHA would stop
the progression of heart disease. And then DHA was associated with
increased risk of prostate cancer, and monumentally failed
to treat macular degeneration. This over-the-top rhetoric
sounded a little suspicious and indeed the paper was retracted
because the author sells some rival supplement that he failed to
disclose, but he does have a point. I covered the fish oil
failure for heart disease. What about the
increased cancer risk? Men with the highest
circulating levels in their blood of the long chain
omega 3 fat DHA were found to be at higher
risk for prostate cancer, though a subsequent compilation
of all such studies suggested EPA, the other major long chain
omega 3 in fish and fish oil may be more closely associated
with increased cancer risk. Either way, these long chain
omega 3’s have been promoted for prevention of heart
disease and cancer, but now that we know that not
only does there appear to be no benefit for death,
heart attack, or stroke, but that there may be an
elevation in cancer risk, the general recommendation to
increase the intake of these fats should consider
its potential risks. How could eating more fish
or fish oil increase cancer risk? Well, there are some industrial
pollutants like PCBs linked to increased prostate cancer risk,
and the primary source of exposure in the general population is
believed to be through diet from fish, meat, and
dairy products. If you do a supermarket survey,
the PCBs, shown in white here, are highest in freshwater fish, and
lowest in vegans — cannibals take note. No, that’s just how they label the
market basket of plant foods, though vegans have been tested and
were found to be significantly less polluted, including the PCB
specifically linked to prostate cancer. But this study here was
done in North American where people don’t
eat a lot of fish, and indeed even the group with the
highest DHA levels weren’t that high. And so maybe the confounding factor
was meat consumption in general, not just fish, and that lower meat
consumption may be a reason for the lower rates of prostate
cancer in the lower DHA group, as the consumption of well-done meat
is associated with an increased risk of prostate cancer and
intake should be restricted. We also used to think omega 3’s
could protect us from arrhythmias — abnormal heart rhythms
like atrial fibrillation. Millions suffer from the condition,
which causes an irregular heartbeat and a higher risk
of stroke and death, but fish and fish oil consumption
does not appear effective for preventing it
or treating it. Other arrhythmias can be life
threatening and cause sudden death. Despite initial encouraging
results, more recent studies have not only failed to reduce sudden
cardiac death with omega 3’s, but actually increased
mortality in cardiac patients. For example, men with heart disease
advised to eat more oily fish or supplied with fish oil capsules
were found to have a higher risk of cardiac death, maybe because of the
contaminants in fish such as mercury? In either case, given the inconsistent
benefits and the potential adverse effects, omega 3’s
must be prescribed with caution and generalized
recommendations to increase fish intake or to take fish oil capsules
need to be reconsidered.