Does Fish Oil Really Cause Prostate Cancer??

by Dr. Jason Barker August 31, 2013

Does Fish Oil Really Cause Prostate Cancer??

You would think so if you only read the headlines made by a recent study published in the July 2013 issue of the Journal of the National Cancer Institute.

But here’s the deal - despite the attention this study generated, it was readily scorned from a variety of sources and should be interpreted with a significant degree of caution for the following reasons:

1. They used a single blood measurement of omega-3 levels and found that men with prostate cancer had ‘higher’ levels. And by higher, they meant a difference of only 0.2%!  Eating a tuna sandwich the day before the blood draw could create such a difference – omega-3 blood levels will fluctuate depending on diet.

2. Still, these are not ‘high’ levels of omega-3 - any country that has a diet based on fish would have incredibly high levels of prostate cancer, and that isn't the case.

3. There are many confounding risk factors (that can influence prostate cancer incidence) in this study that may have influenced the study outcome, such as:

  • 80% of the subjects with cancer were obese or overweight.
  • 64% of the subjects with cancer regularly consumed alcohol.
  • 53% of the subjects with cancer were smokers.
  • 30% of the subjects with cancer had at least one first-degree relative with prostate cancer.

3. Overall, the outcome of this study is in stark contrast to other omega 3 studies that show a protective benefit against prostate cancer. Furthermore, when one considers the number of additional studies that display the anti-inflammatory effects (important for athletes!) of omega-3 fatty acids and the fact that study investigators did not suggest a credible biological mechanism, it is difficult to understand exactly how omega-3 fatty acids could have led to increased prostate cancer in these subjects.

Lastly, the identification of one physiologic marker (elevated plasma omega-3 levels), that is easily influenced by diet and measured at only one point in time, in a group of subjects with a particular condition (prostate cancer) does not prove causation in any way.

Based on these weaknesses, and the known wide-ranging health benefits attributable to omega-3 fatty acids in many other studies, it would be unwise to discontinue eating fish or taking omega-3 supplements based on this study alone.

To note, the health benefits from fish-derived omega-3 oils should be obtained from fresh fish, not salted or smoked.  Additionally, all oils are prone to oxidation in the body. Therefore, a diet rich in antioxidants is always a good idea. You can get plenty of antioxidants from darkly colored fruits and vegetables.

Dr. Jason Barker
Dr. Jason Barker


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