By Chris S.
Prostate and other cancers thrive in an inflammatory environment, so it is not surprising that reducing cellular inflammation has been shown repeatedly to decrease cancer risks. The best-researched natural anti-inflammatory agents are Omega-3 fish oil, vitamin D and plant based polyphenols. High levels of Omega-3 have consistently been associated with reduced mortality in prostate cancer (1). A review of 19 studies published in 2010 showed a 63% reduction in mortality in those with a high fish intake (2).
How then do we explain the recently published findings from the SELECT study (3), which appears to suggest the opposite?
The answer is surprisingly simple – none of the participants in the SELECT study actually had high levels of Omega-3. There were small differences between the cancer and non cancer groups which although found to have statistical significance have no biological meaning. If higher levels of Omega-3 reduce prostate cancers as previous research suggests, having a low level is hardly likely to do the opposite. The problem with the SELECT study is that the authors have identified low Omega-3 levels as high. This is not even mistaking apples for pears, it is mistaking an apple for a candy bar! All of the participants in this study had the kind of Omega-3 levels you find in the West which means they were still all deficient to some degree.
If the conclusion about Omega-3’s role in prostate cancer was true we would see a much higher incidence of the disease in countries such as Japan and Greenland where the Omega-3 levels in the diet are much higher. In fact, the opposite is true (8). When Japanese men emigrate to the USA where the diet is much lower in Omega-3 (the level in the SELECT study) the incidence of prostate cancer increases dramatically (9).
Furthermore, It is complete nonsense to draw any conclusion about Omega-3 and cancer from this data, period. SELECT was not even designed to look at Omega-3 so they did not collect data on seafood or fish oil intakes. The slightly higher levels of Omega-3 in the cancer group may be due to increased fish oil intake in the cancer patients. These patients often take fish oil supplements, as there is evidence that Omega-3 can improve outcomes with chemotherapy and reduce the weight loss associated with cancer (4,5). It has also been shown in breast and prostate cancer that they can reduce the chance of the disease spreading (6,7).
This study does not reverse all of the previous findings about inflammation, Omega-3 and cancer. This is just a very bad example of research providing new information and shows how misleading science can be when the statistics associated with it are not dealt with context and biological relevance. It has no doubt caused confusion and distress to a vulnerable patient group and is enough to give science a bad name.
Ed. note – For even more articles on this this topic:
“If you listen to this study, you should not only cut Omega-3 but also start smoking cigarettes and drinking more.”
Dr. William Harris, Professor, Sanford School of Medicine, writes a great piece on ‘Omega-3 Fatty Acids and Risk for Prostate Cancer‘
- Chavarro JE et al. A 22-y prospective study of fish intake in relation to prostate cancer incidence and mortality. Am J Clin Nutr 2008; 88: 1297–303.
- Szymanski KM, Wheeler DC, Mucci LA. Fish consumption and prostate cancer risk: a review and meta-analysis. Am J Clin Nutr. 2010 Nov;92(5):1223-3
- Brasky TM, Darke AK, Song X, et al. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT Trial. J National Cancer Inst Online. July 10, 2013 doi: 10.1093/jnci/djt174
- P Bougnoux Improving outcome of chemotherapy of metastatic breast cancer by docosahexaenoic acid: a phase II trial Br J Cancer. 2009 December 15; 101(12): 1978–1985.
- Colomer R N-3 fatty acids, cancer and cachexia: a systematic review of the literature. Br J Nutr. 2007 May;97(5):823-31.
- Mandal CC Fish oil prevents breast cancer cell metastasis to bone. Biochem Biophys Res Commun. 2010 Nov 26;402(4):602-7. doi: 10.1016/j.bbrc.2010.10.063. Epub 2010 Oct 28.
- Nakajima T Eicosapentaenoic acid inhibits voltage-gated sodium channels and invasiveness in prostate cancer cells. Br J Pharmacol. 2009 Feb;156(3):420-31. doi: 10.1111/j.1476-5381.2008.00059.x. Epub 2009 Jan 16.
- Dewailly E, Mulvad G, Sloth Pedersen H, Hansen JC, Behrendt N, Hart Hansen JP. Inuit are protected against prostate cancer. Cancer Epidemiol Biomarkers Prev 2003;12:926–7
- Shimizu H, Ross RK, Bernstein L, Yatani R, Henderson BE, Mack TM. Cancers of the prostate and breast among Japanese and white immigrants in Los Angeles County. Br J Cancer 1991;63:963–6