Rethinking the Benefits of Fish Oil – Again

Categories: Summer/Fall 2018
A new analysis of major clinical trials found that fish oil supplements did not provide protection against heart disease in patients with a history of cardiovascular events. Earlier studies have also linked higher omega-3 fatty acid levels and prostate cancer, yet conflicting evidence signals that the debate over fish oil, heart disease, and prostate cancer is bound to continue.

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The new analysis was published in JAMA Cardiology and examined data of nearly 78,000 patients with a history of heart disease, stroke, or diabetes who participated in 10 different trials. The author compared rates of coronary heart disease, stroke, and major vascular events between patients who did and did not take omega-3 supplements, such as fish oil pills. Ultimately, the study found no association between omega-3 fatty acids and a reduced risk of heart disease or major vascular events. The findings provide “no support for current recommendations for the use of such supplements in people with a history of coronary heart disease,” the authors concluded.

The popularity of fish oil dietary supplements appears to be rising, with approximately 8% of adults in the U.S. taking the supplements in 2012 (compared to less than 5% in 2007).

The debate over a prostate cancer link

Previous QUEST articles have covered the possible link between prostate cancer and omega-3 fatty acids. For example, a 2013 study found that men with high concentrations of omega-3 fatty acids in their blood had a 43% greater risk of having prostate cancer, and a 71% higher risk of having high-grade prostate cancer. The study did not demonstrate that the fatty acids caused the cancer; the reason for the association is still unknown.

However, preliminary studies from UCLA suggest that men with certain genetic variants may actually benefit from taking fish oil supplements. Specifically, patients whose prostate tumors were infiltrated with type M2 macrophages may see a benefit if they take omega-3 supplements.

Ultimately, the confounded and conflicting data suggests that patients should talk to their doctors before taking fish oil supplements to discuss the potential benefits and drawbacks.

For further details on association between omega-3 fatty acids and prostate cancer, search for “fish oil” on the URF website: or read “The Debate Continues: Prostate Cancer and Omega-3 Fatty Acids” in the Spring 2014 QUEST and “Study Links Omega-3 Fatty Acids and Prostate Cancer” in the Winter 2013 QUEST.

What are omega-3 fatty acids?

Omega-3 fatty acids are involved in important functions in the body, from being in cellular membranes, developing brain function, and reducing inflammation. Because they are “essential” fatty acids, people can only get omega- 3 fatty acids from eating them; our bodies cannot produce them on their own. The acids are found naturally in foods such as fish, flaxseed, and walnuts.

Most people in the U.S. get enough omega-3 fatty acids from eating food, and the best place to get your nutrients is from eating a healthy diet. Unlike supplements, food contains vitamins, minerals, dietary fiber, and other helpful substances. (from the U.S. Department of Agriculture) recommends choosing seafood at least twice a week as a protein source. (Guidelines regarding mercury levels in certain seafoods are also available on

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