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Can fish oils increase prostate cancer risk?

Posted by Brady Bunch on

Eamonn Brady is a pharmacist and the owner of Whelehans Pharmacy, Pearse St, Mullingar. If you have any health questions e-mail them to

A recent study by Brasky et al. in the Journal of the National Cancer Institute indicated an increased risk of prostate cancer for men who used omega 3s. This has raised concerns about how safe fish oils are for men.

What the experts say

Many experts have indicated that this study is flawed. The study was not designed to investigate the role of Omega-3 intake on prostate cancer. Fish oil supplements were not used as part of the study. Only plasma Omega-3 was measured, these levels really only reflect the Omega-3 consumption of your last meal and not a true reflection of your Omega-3 consumption.

According to Dr James O’Keefe, Director of the Preventative Cardiology Programme at St Luke’s Mid-American Heart Institute, the study only showed miniscule differences in omega-3 blood levels. The omega 3 levels found in patients’ blood was the equivalent of having no fish intake or fish oil supplementation. Dr O’Keefe explains that previous studies indicated that omega 3 actually has a protective effect against prostate cancer. He says that higher omega 3 levels have consistently and strongly correlated with lower risks of cardiovascular mortality.

According to Professor Clemens von Schacky, a German Cardiologist, “virtually every male gets prostate cancer, provided he lives long enough to get it. Age was not properly handled as a risk factor in the study mentioned.”

Dr Harry Comber, Director of the National Cancer Registry in Ireland, said he was loath to give advice to patients to take action on the basis of a single study."People should not change their behaviour based on a single study. I would take it with a little bit of caution. It is suggestive but not definitive one way or the other."


It should be noted that the best way to get omega 3 is naturally through your diet. Omega 3 fatty acids are primarily found in oily fish such as salmon, fresh tuna, mackerel, herring, sardines and pilchards. We should eat two portions of fish per week, one of them oily. You should only use omega 3 supplements if you do not eat sufficient oily fish or other sources or omega 3 such as flaxseed.

There are facts about omega 3s that seem to be at odds with this study. For example, Japan has one of the highest intakes of Omega-3 fish oil with the lowest incidence of prostate cancer in the world. Ireland has one of the lowest intakes of Omega-3 fish oil yet has a high incidence of prostate cancer. Further studies are warranted.  I would advise men who have a family history of prostate cancer or who are at higher risk or prostate cancer (as indicated by blood tests) are best to avoid fish oil supplements.

The advice in this blog is the opinion of Eamonn Brady; consult with your doctor before making any changes

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