Does Fish Oil Cause Prostate Cancer?


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Every morning I wake up and take two 1250mg Omega-3 fish oil pills. It is a habit that was formed through the insistence by my mother, who deeply cares about my well being. Consuming fish oil is commonly seen as a positive action and is thought to benefit one’s health in a number of ways including lowering triglyceride levels, decreasing heart disease risk, and easing symptoms of other various disorders and diseases (Web MD).  Whenever I take any supplement to my diet I want to be sure that it is beneficial to my health. There has been some confusion recently over some possible negative health effects that fish oil supplements could impose upon the body. I wanted to look at some of those ideas and hopefully debunk these possibilities. One possible health effect being studied is the potential positive correlation between Omega-3 fatty acids, and an increased risk of prostate cancer in men. Omega-3 fatty acids are found in fish oil capsules. The Journal of the National Cancer Institute, a subdivision of the Oxford University Press conducted a study observing plasma phospholipid fatty acid intake and prostate cancer risk.

When thinking about causality, we assume that fish oil capsules could be increasing someone’s risk of developing cancer, but is there a possibility that the risk of cancer is causing someone to take fish oil capsules? What if people susceptible to prostate cancer take fish oil because they think it will decrease their risks of developing the disease? Because of this, it does not appear that we can rule out reverse causality. The study accounted for a handful of possible confounding variables including age, race, education, BMI, smoking status, alcohol consumption, etc.. Hopefully by accounting for those variables, the study has more accurate results.


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The conclusion of the study found that there is a link between high blood concentrations of  LCω3PUFA (ω3 polyunsaturated fatty acid) and increased risk of prostate cancer.The P-value was less than .05, so the results of the study were deemed statistically significant. Now we need to decide whether this study has discovered something or if it is simply a Type 1 error. We have a five percent chance that the conclusion reached is a Type 1 error (false positive).

The group of researchers at the Journal of the National Cancer Institute did not clearly present a mechanism for the possibility that fish oil causes prostate cancer. However, mechanisms do not always need to be known to prove that a correlation is causal.

It is evident that more research needs to be done to draw a stronger inference on whether this supplement could cause prostate cancer. If future studies find similar results, the likelihood of correlation between the two will increase exponentially.

For myself, I will most likely continue to take fish oil capsules daily due to the many benefits I believe it has for my health. If you do take fish oil capsules, I recommend you keep your eyes open for new studies that are likely to emerge in the future. If you are a male with a known family history of prostate cancer, you might want to cut back on fish oil consumption until we understand its effects better.

Works Cited:

“Fish Oil Uses and Side Effects.” Web MD,

“Plasma Phospholipid Fatty Acids and Prostate Cancer Risk in the SELECT Trial.” Journal of the National Cancer Institute, 2013. SIRS Discoverer, Accessed 14 Oct. 2016.

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