hand holding a gel capsule with fish oil

Fish Oil and Prostate Cancer

Last updated: April 2023

Fish oil from fatty fish contains omega-3 fatty acids. Omega-3 fatty acids are important for heart health. They reduce the risk of dying from heart disease. They may also be helpful for other conditions.1

Concern about men consuming fish oil grew because of a study in 2013. This study found a link between omega-3 levels and prostate cancer. Authors of the study encouraged men to avoid fish oil supplements.2

However, the study had major flaws. New research has shown no link between fish oil and prostate cancer. Fish oil is still generally safe and important for your overall health. Talk to your doctor about the benefits and risks of fish oil.3,4

What are fish oil supplements?

Fish oil comes from oily fish and certain shellfish. Examples of oily fish include salmon, tuna, and trout. Fish oil is rich in omega-3 fatty acids. Omega-3 fatty acids reduce inflammation and help with muscle activity.1

Our body cannot make omega-3 fatty acids on its own. We get omega-3 fatty acids from food. Fish oil contains 2 omega-3 fatty acids: docosahexaenoic acid (DHA) and eicosapentaenoic acid. Some nuts and vegetable oils contain another omega-3 fatty acid: alpha-linolenic acid.1

Many people take fish oil supplements to increase their omega-3 intake. This is because of potential health benefits. Fish oil has been researched for its potential benefits for:1

  • Heart disease
  • High blood pressure
  • High triglycerides and cholesterol
  • Rheumatoid arthritis
  • Anxiety and depression

Whether fish oil has a benefit for some of these conditions is uncertain. The most established benefit is that it lowers the risk of dying of heart disease.1

Why is there concern about fish oil and prostate cancer?

Concern about fish oil and prostate cancer comes from a flawed 2013 study. This study showed a link between blood DHA levels and prostate cancer. The authors concluded that omega-3 fatty acids play a role in prostate cancer.2

However, this study had serious flaws. First of all, it showed correlation but not causation. That is, it showed a link between omega-3 levels and prostate cancer. But it did not prove that fish oil supplements increase the risk of prostate cancer.5,6

For example, it is possible that metabolic factors cause omega-3 accumulation and prostate cancer. But that would not mean that omega-3 fatty acids play any role in prostate cancer.5,6

Other flaws of the study are that it:5,6

  • Was not a controlled clinical trial (did not split participants into groups who received fish oil supplements versus a placebo)
  • Did not assess fish oil consumption or supplement use (few of the participants actually used fish oil supplements)
  • Used a test for omega-3 levels that does not accurately assess long-term dietary intake
  • Found no meaningful difference in omega-3 levels between people with and without prostate cancer

What does recent research say?

Many other studies have shown no link between omega-3 fatty acids and prostate cancer. In fact, omega-3 fatty acids may reduce the risk of dying from prostate cancer. Groups of people (populations) with high fish consumption – such as Japanese men – have a lower risk of dying from prostate cancer.3,4

Newer, larger studies than the 2013 one used better tests for omega-3 levels in the blood. These studies have shown no link between omega-3 levels and prostate cancer. The benefits of omega-3 fatty acids for heart health are well-established. Concerns about prostate cancer should not outweigh these benefits.3,4

How should I consume fish oil?

Talk to your doctor about fish oil. It is generally safe and healthy. The American Heart Association recommends eating fatty fish twice a week. This can provide enough omega-3 to help your heart.7

Fish oil supplements can increase your omega-3 fatty acid intake. This may be helpful for people with heart conditions. Tell your doctor about your full health history before taking fish oil supplements. This includes the medicines you take and other medical conditions you have. Fish oil supplements can have mild side effects, including:1

  • Fishy aftertaste
  • Bad breath
  • Heartburn
  • Nausea and diarrhea
  • Rash

These are not all the possible side effects of fish oil supplements. Talk to your doctor if you notice any changes while taking fish oil supplements. Ask your doctor whether the benefits outweigh any potential risks and side effects.

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