Fish Oils, which are high in omega-3 fatty acids, have long been praised for their great health benefits. A variety of studies have linked omega-3s with reducing the risk of heart disease and depression, lowering cholesterol levels and body weight, and more. But in the past few years, there’s been a growing body of evidence that when it comes to prostate cancer, omega-3s may be doing more harm than good. Way more harm.
It started in 2011, when one study found that men who consumed high levels of omega-3s—either by eating fatty fish (like salmon or sardines) or taking fish-oil supplements—had a higher risk of developing prostate cancer than men who ate less fish oil. A large-scale study done in Europe found similar results. And in another US study, researchers at the Fred Hutchinson Cancer Research Center in Seattle confirmed that men with high blood levels of three oils: EPA, DPA, and DHA, had a 71% higher risk of developing the most aggressive and fatal type of prostate cancer than men with low levels of those oils. They also had a 44% increase in less aggressive forms of the cancer. To put things into perspective, the difference between the highest and lowest blood levels of omega-3s was roughly the amount that would be in two servings of salmon per week.
No one seems to understand completely how the fish-oil-prostate-cancer connection happens, but they speculate that it may have something to do with the way tumors are formed in the body. The study’s authors wrote that, “the use of nutritional supplements may be harmful,” and that “recommendations to increase long-chain omega-3 fatty acid intake, in particular through supplementation, should consider its potential risks.”
Other sources of healthy fats, such as vegetable oils, seeds, and avocados, had no negative impact on prostate cancer. In fact, these “good” fats may actually reduce the risks. We’ll talk more about that in a future article on this site.
If your healthcare provider has recommended that you take fish-oil supplements or that you eat more than two servings of fish per week, we recommend that you talk with him or her about whether or not the benefits in other areas outweigh the increased prostate cancer risks. For example, if you have a family history of heart trouble but no family history of prostate cancer, you may be okay. But don’t make any major changes without consulting your provider.
The study was published in the Journal of the National Cancer Institute.