What does Dr Gerald Lewis think about the article on Omega 3 and prostate cancer

Response to the article “Fish oil supplements cause prostate cancer.”  Dr Gerald Lewis FRCP, FRACP, MD

Another futile attempt to dissuade people from taking nutritional supplements!

A recent paper in The Journal of the National Cancer Institute has been blown out of all proportion by the international press, with headlines stating – “Taking fish oil supplements can increase your risk of developing prostate cancer by 70%” – even though the study did not ask the patients if they took fish oil supplements!

These are my comments on this recent "study".  I have placed this word in quotation marks because it is not a study, but data dredged from an earlier trial. The medical profession, particularly the scientific members, discourage and ignore such data dredged information. The study suggests that eating fish and taking fish oil supplements increases the risk of people developing prostate cancer. It does nothing of the sort, but again reveals the depths to which vested interests will go in an attempt to stop people looking after their own health.

It is well-known that omega-3 oils (fish oils) are beneficial in many diseases including heart disease, sudden cardiac death, some neurological conditions, diabetes, asthma and many other diseases.  Most medical practitioners recommend their patients take omega-3 oils as part of a healthy diet. Then along comes a study such as this!

It claims that taking fish oils, and fish oil supplements, increases the risk of developing high-grade prostate cancer . This would suggest that everybody who eats a lot of fish (Japanese, Indians living by the coast, Inuit and similar fish eating populations) would have a higher incidence of prostate cancer. It is the reverse, all cancers are reduced in these people, including prostate cancer.

So why is this information, which interestingly was 'leaked' early to the press and TV and made international headlines all around the world, of such great international interest? 

The principle authors of this study are the same as the authors of an earlier study in 2011 which looked at patients in the finasteride trial. In this trial published in 2011 18,000 people received either finasteride, a drug which was hoped might reduce the development of prostate cancer, or placebo tablets. In the trial, which involved patients having prostate biopsies, 1800 patients developed prostate cancer and these were compared with 1800 controls. The cancer patients did have a slightly higher incidence of the blood fats associated with eating fish. Interestingly the cancer patients also appeared to be protected by eating trans-fatty acids, smoking and drinking alcohol !!!

This most recent study published in 2013 again was dredging up the data from another trial (the SELECT trial) which was looking, at the effects of selenium and vitamin E to see whether they were protective in the development of cancer. The trial was stopped early, because the investigators felt that they were not going to achieve a result. It was an enormous trial, involving 35,000 people in the Americas. Of these 834 developed prostate cancer, 156 of these were classified as high-grade. 1300 people were selected from the study as controls. There appeared to be a higher incidence of high-grade cancer in patients whose blood fats indicated a high fish oil intake.

Only one blood sample was taken during the entire trial, and at no stage were people asked whether they took fish oil supplements or not!

The raised level of fish oil fat could have resulted from eating a fish meal or fish sandwich! 

Is it possible to make such claims from 156 patients in a 35,000 population trial?

Although there may have been a slight increase in the number of patients with high-grade prostate cancer, there was a slight decrease in cancer prostate deaths, although this was not significant.

There have been numerous studies looking at fish oils and cancer, including some specifically looking at prostate cancer.  The results have been wildly differing, some suggesting a 70% increase in prostate cancer (this trial) while others have shown a 60% protective effect. Not one has shown an increase in deaths.

This trial should be filed among all the others to create a database, but certainly in no way proves that fish oils, and particularly fish oil supplements, increase prostate cancer deaths.

The medical profession has always insisted that for a trial to have meaning, it should be designed from the beginning to show the result. If researchers continue to dredge through the data, eventually they will come up with something which is surprising. In this trial it appears this is what they have done.

The most important thing is that populations who eat a lot of fish have a lower incidence of prostate cancer. It is difficult to understand how the authors of the study can explain this, they do not attempt to do so in their paper.

There are numerous studies showing that fish oils are beneficial in many diseases, including cancer.  One danger of eating fish is the possibility of mercury poisoning, hence the benefit of pure high quality pure fish oil supplements.

The international response to such a dubious study gives an indication of the feeding frenzy which is generated by any paper criticising complimentary medicine, almost certainly fuelled by a pharmaceutical industry which is rapidly running out of ideas.