Poor Quality Omega-3 Prostate Study

In 2013, the Journal of the National Cancer Institute published a study linking omega-3 fatty acids to prostate cancer. Two years have passed since the release of this study, yet the repercussions have lingered.

A perfect example: A colleague of Brian Matthew’s recently visited his cardiologist. This colleague (let’s call him “Jim”) has already had a heart attack and diligently takes his fish oil every day, since science supports its use as a preventive measure against repeat heart attack.

After running down the list of all the medications and supplements he takes, Jim’s cardiologist looked up and said, “You know, a study came out a couple years ago linking omega-3s to prostate cancer. You may want to cut back on those.”

Mind you, this cardiologist is one of the most respected in the area. Now remember, solid research—including randomized clinical trials—reveals the benefits of omega-3s (such as certain fatty fish and omega-3 supplements) for heart health. And prevention studies suggest that omega-3s significantly reduce the number of deaths from heart disease and all other causes. But many in the medical community and beyond have “fallen prey” to misinterpretation and over-blown reporting of the data in that prostate cancer study.

Here are a few facts about that study.

The study was a clinical trial design to determine the impact of selenium and vitamin E on prostate cancer. Neither fish nor omega-3 fatty acid supplements were given, so it was not a clinical trial to measure the effect of omega-3s on prostate cancer. In fact, the data was based on circulating fatty acids in plasma that had only been measured once in the 7-12 years of the study.

So this was a population-based study that examined whether there was an association between circulating omega-3 levels and the incidence of prostate cancer. The results from the study showed that all groups had low circulating levels of omega-3 fatty acids, and there were very small and likely biologically insignificant differences (~0.2%) between the prostate cancer group and the control group.

If we are to learn from population-based studies, it would seem much more important to examine populations that consumed high amounts of omega-3s and compare them to those who ingest low concentrations of omega-3s. When we do that, populations that ingest traditional Japanese or Mediterranean diets (which contain relatively high amounts of omega-3s) have some of the lowest incidences and death rates from prostate cancer among all global populations.

Most Prostate Cancer Studies Suggest Omega-3s Are Beneficial

While population-based studies have their place, studies that actually test the effect of fish or fish oil consumption on prostate cancer provide much more meaningful information.

In a 2010 meta-analysis (which combines results from several studies), fish oil or fish consumption was associated with a 63 percent reduction in mortality due to prostate cancer. Among the 12 studies cited was one that followed 6,272 Swedish men for 30 years. This study showed that those who ate no fish had a 2- to 3-fold increase in the risk of developing prostate cancer compared to those who consumed large amounts of fish.

In another study that followed 47,866 men over 14 years, omega-3 intake was associated with a 26 percent reduction of developing prostate cancer. And in a study that looked at 20,167 men who participated in the Physician’s Health Study, the men who ate fish five or more times per week had a 48 percent lower risk of developing the disease compared to those who ate fish less than once per week. A similar association was found between fish consumption and prostate cancer mortality.

Finally, a meta-analysis published earlier this year looked at 12 self-reported dietary intake and nine biomarker studies (for a total of approximately 460,000 men). The researchers discovered no link between omega-3 fatty acids and prostate cancer in any of the trials.

Don’t Stop Taking Your Omega-3s

It is a shame that ONE study that was not even designed to study the impact of fish oil on prostate cancer could get so much attention and potentially affect the health decisions of millions of people worldwide. The science taken as a whole reveals that you should not let this study deter you from using omega-3s and eating fatty fish such as salmon, mackerel, and albacore tuna.