Is There a Link Between Fish Oil and Prostate Cancer?
A study published online in the Journal of the National Cancer Institute suggesting that fish oil consumption increases the risk of prostate cancer has garnered many headlines. Medical research is replete with studies that seemingly contradict one another, and it’s important to look at the weight of the evidence as other studies have shown that fish oil reduces prostate cancer risk. Here are four points to consider regarding a possible link between fish oil and prostate cancer.
With regards to the study linking fish oil to prostate cancer the data were pulled from a larger study completed over seven years and originally published in 2008. That study is called the SELECT Trial (selenium and vitamin E Cancer Prevention Trial) and is the largest trial to date on the prevention of prostate cancer. The SELECT Trial was not specifically designed to study the link between fish oil and prostate cancer, however. This raises questions as to the validity of findings linking fish oil consumption and prostate cancer as not all known predictors for prostate cancer were corrected or adjusted for between the men who were taking fish oil and those who did not.
Secondly, it is known that many fish oil products are not pure and have contaminants in them. The quality of the fish oil taken by men in the SELECT Trial is not known. So it is entirely possible that the link between fish oil and prostate cancer may be related to impurities (mercury) in the fish oil and not the omega-3 fatty acids in the fish oil.
Let’s assume that there is a true causal relationship between fish oil and prostate cancer. If you’re a man currently taking fish oil should you stop it? Risks need to be weighed. Fish oil is an anti-inflammatory and has proven effects in heart disease prevention and other health benefits. Though prostate cancer will affect one in every six to seven men, heart disease is still more common. Thus, the overall benefit of fish oil still outweighs the risks – assuming there are risks.
Lastly, results of medical research are most valid when the conditions of the study can be replicated in real life. Also, drawing conclusions from a study population and applying it to the individual is always challenging. We have natural studies on populations like Inuit Eskimos whose diets are extremely high in fish oil mainly from eating fish, but also from supplementation. They have lower rates of heart disease and prostate cancer. Eskimos who have migrated to industrialized nations and adopt an industrialized diet have higher rates of prostate cancer and heart disease than their relatives who are faithful to their native diets.
In my opinion, there is not enough good evidence to stop taking fish oil supplements, though I do strongly recommend buying a high quality brand to avoid the potential problem with impurities..
One take home message, though from this recent study, is that we should look for nutrition first from the foods we eat and not from a pill or capsule. Supplements are to supplement the diet not replace it and sometimes we do go too far thinking supplements are the answer to everything.
For more critique of this study go to Badly Flawed Study of Fish Oil Leaps to Wildly Unsupported Conclusions About Cancer. Or listen to this audio of Michael Savage’s interview with Anthony Victor D’Amico, MD.