does fish oil cause prostate cancer?...

Question: I have recently read many articles about a study showing that fish oil raised the risk of aggressive prostate cancer. I have been taking omega-3 supplements for heart health but stopped when I heard the news about its effect on prostate cancer. What is your opinion about this research?

Answer: The American study in question, published online on July 10 2013, in the Journal of the National Cancer Institute, certainly hit the headlines in print, on the radio and on TV. Much of the news coverage did not accurately reflect the findings. Aside from the sensationalist way it was reported the study itself has serious shortcomings.

As reported the study found that men who had high concentrations of omega-3s in their blood had a risk of developing prostate cancer that was 43% higher than men who had the lowest blood levels of these fatty acids. Even more alarming was the finding that men with the highest blood levels of omega-3s had a 71% higher risk of aggressive, possibly fatal prostate cancer than those with the lowest levels.

The select study was not set up to evaluate fish or fish oil intake in the study group, its relevance is not as significant as studies designed to specifically determine the impact of omega-3 fatty acids on prostate cancer risk.  As a matter of fact there is no evidence that anybody in the study took fish oil supplements or even ate fish!

This research did not actually compare the cancer risk of men who ate fish or took fish oil supplements to men who didn’t eat fish or take supplements. In fact, the researchers provided no information regarding intake of fish or fish oil supplements by the men in the study group. The research team looked at blood levels of omega-3s among men who were enrolled in the Selenium and Vitamin E Cancer Prevention Trial, a large National Cancer Institute trial aimed at determining whether either of those supplements alone or in combination lowered the risk of prostate cancer.

The authors of this recent study based their conclusions on the analysis of a single blood sample from each of 834 men in the study diagnosed with prostate cancer through 2007 and from a corresponding group of 1393 healthy men who participated in the study and were matched by age and race to the men who developed the disease.

The fats the research team focused on were plasma phospholipid fatty acids, which tell you that an individual recently consumed fish or fish oil but don’t really give you an accurate indication of the long term use of fish oil supplements, or a diet that includes regular servings of fish. The study found that the mean blood level of plasma phospholipid fatty acids were 4.66% in the men with prostate cancer and 4.48% in the healthy controls, a difference of not quite 0.2%. That is a very small difference on which to base the suggestion, as these researchers did, that omega-3s “are involved in prostate tumorigenesis” and that those who recommend that “men who consume omega-3s should consider its potential risks”.

These results appear to be an unfortunate combination of questionable science, unwarranted conclusions, and dreadful media coverage. The well-documented evidence for myriad benefits of high dietary intake of omega-3 fatty acids on both physical and mental health is very strong. The best thing about the flawed study is that it will stimulate more research into the role of omega-3 fatty acids in prostate health. 

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