Does Fish Oil Cause Prostate Cancer?

The media has been putting up headlines like:

Fish Oils may increase prostate cancer risk – CNBC July 11 2013

Link to Prostate Cancer brings more bad news for fish oil story – Forbes July 11 2013

But, does fish oil really increase prostate cancer risk? We have been asked by our clients what our views are regarding this piece of news.  The study was published in the Journal of the National Cancer Institute entitled “Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT trial” and has generated lots of recent media interest and inquiries from the public.

After reviewing all the information we could get on this study and in consultation with our scientific advisors, we believe that the precautions against omega-3 consumption in this study are largely without merit.  You should be confident that fish oil is still a beneficial supplement.

This study and the conclusions drawn contain many flaws, including:

• This is not an intervention study where the participants were given fish oil to evaluate their prostate cancer risk.  It was merely an observational study to look at the Selenium and Vitamin E Cancer Prevention Trial (SELECT) where the levels of plasma phospholipids were measured.  Observation does NOT mean causation.  There can be other confounding factors in the study that have caused that observation.
• Plasma phospholipids is a measure that can vary significantly depending on when your last meal of omega-3 or fish or fish oil is. These levels can increase or decrease, based on a single meal within a 48-hour period. 
• The researchers base their conclusions on very small differences in mean omega-3 blood plasma phospholipid levels. The increased prostate cancer risks they ascribe to men who consume large amounts of omega-3 is based on a level of 4.66% in the cancer group, versus a level of 4.48% in the control group.
• If high levels of omega-3 indeed increases the risk of prostate cancer, then countries with high consumption of omega 3 like Japan and Scandinavia should have high rates of prostate cancer.  However, the reverse is true.  It is the countries with low consumption of omega-3 and high consumption of trans and saturated fats that have high incidence of prostate cancer.
• This is a small study and the conclusions are not keeping up with the rest of the literature on cancer risk and omega-3 fish oil consumption.  8 other major studies involving 78,000 participants have found NO increase in cancer risk.

The researchers have ignored many studies collated over many decades of studies of Omega-3 and its health benefits to publicise conclusions that contradict other better designed research.  However, we do advise our patients to be careful about the source of fish oil purchased.  Since the publicity of the health benefits of Omega-3, many companies have jumped onto the bandwagon and there is no shortage of brands of Omega-3 in the market, from grocery lines to properly tested therapeutically designed Omega-3 we dispense in our clinic.  You get what you pay for, not all Omega-3 fish oils are the same.