Fish oil, which contains the omega-3 fatty acids DHA and EPA, has long been touted as beneficial for cardiovascular health, mental health (including depression and Alzheimer’s disease) and arthritis, just to name a few.  

New research suggests high doses of the compound can increase one’s risk of high-grade prostate cancer.  But before you abstain from all fish and omega-3 consumption, let’s take a closer look.

The terms “fish oil” and “omega-3 fatty acids” are often used interchangeably, which can actually be misleading.  Fish and fish oil contain the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).  The third omega-3 fatty acid, alpha-linolenic acid (ALA) is found in nuts and vegetable oils and can be converted, in small amounts, into DHA.  

Therefore, when using the term “fish oil,” you are actually only referring to two of the three omega-3s.  Most of the evidence supporting the health benefits of omega-3s refers to the two components of fish oil: DHA and EPA, whereas evidence supporting the health benefits of ALA is lacking.

The American Heart Association recommends consuming fish (particularly fatty fish like salmon) twice a week and the Food and Drug Administration (FDA) considers up to 3 grams of fish oil per day “generally regarded as safe.”  Consumption of more than 3 grams per day can increase your risk of bleeding and should be discussed with your doctor first.

Researchers at the Fred Hutchinson Cancer Research Center looked at a subset of the Selenium and Vitamin E Cancer Prevention Trial (SELECT) population: 834 men who developed prostate cancer and 1,393 randomly chosen men who did not have cancer.  They found that men who had the highest levels of omega-3 fatty acid compounds had a 71 percent increased risk of high-grade prostate cancer and a 43 percent increase for all prostate cancer.

It’s important to remember that this research did not establish a causal relationship between omega-3 fatty acid consumption and prostate cancer, and while these statistics are indeed alarming, a few more questions need to be answered.  

More research is needed into why such high concentrations of omega-3 fatty acids are associated with an increased risk of prostate cancer, especially high-grade disease. We need to understand the biological mechanism behind the findings and how consumption of omega-3s affects men who have already been diagnosed with prostate cancer.

Different people may have different levels of omega-3 fatty acids in their blood despite similar intake, so talk to your doctor about before beginning or discontinuing use of these supplements or general fish consumption.