hand holding a gel capsule with fish oil

Fish Oil and Prostate Cancer

Last updated: April 2022

You might have heard that the omega-3 fats that are found in fish have a positive impact on health, but recent research has cast some doubt on that claim for men with prostate cancer. In two recent studies, researchers have found a link between men with prostate cancer and men who have high levels of omega-3 fats in their blood.

Research on fish oil

One study from researchers at the Fred Hutchinson Cancer Center shows that men with highest levels of omega-3 fat in their blood samples were 43% more likely to be diagnosed with prostate cancer than men with the lowest levels of omega-3 fat in their blood.1This finding is interesting since the study itself was designed to see if taking selenium or vitamin E might prevent men from developing prostate cancer. An additional measure was to test the men’s blood specimens for omega-3 fat content.

How do omega-3s work?

The omega-3 fats that are found in fish and fish oil are actually three different types, which are frequently analyzed separately in medical studies because these types are associated with different health effects. These subtypes are: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA).

Normally omega-3s have anti-inflammatory properties and that is why they are considered to be an important part of a diet that can be helpful when someone has cancer. One of the ongoing research challenges is being able to demonstrate whether omega-3s that are available through the use of fish oil supplements provide the same protective effects as those naturally found in eating fish.

Other studies have found that fish oil supplements do not have a protective effect for cardiovascular problems, possibly because the omega-3s found in fish have different properties that are not the same as those extracted for supplements.2

For prostate cancer, the picture is a little less clear. Enzymes that desaturate fatty acids convert ALA into EPA and DHA can be upregulated in some cancer cells, presenting the possibility that the prostate cancer itself might raise omega-3 levels, not the omega-3 levels that increase the risk of prostate cancer.3

Omega-3s from fish vs. supplements

Researchers have hypothesized that higher intakes of omega-3s from either foods or supplements might reduce the risk of cancer due to their anti-inflammatory effects and potential to inhibit cell growth factors. Results from observational studies however, have been inconsistent and vary by cancer site and other factors, including gender and genetic risk.3 Other studies have shown that suggesting that omega-3s might increase the risk of certain cancers such as prostate cancer.

In another study of over 47,000 men aged 40–75 years, those who consumed fish more than three times per week had a lower risk of metastatic or advanced prostate cancer than those who consumed fish less than twice per month. However, men who used fish oil supplements did not have a decreased risk of prostate cancer.3

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