By: Dan Sperling, MD
A 2013 study by Brasky et al[i] on the relationship between omega-3 fatty acids and increased risk in prostate cancer raised a national furor. Omega-3 fatty acids are common in marine and plant life oils, and are generally held to be of great health value due to their anti-inflammatory properties. Fish that are particularly rich in omega-3 include salmon, trout and fresh tuna; many people consume over-the-counter fish oil supplements to boost cardiac health. The Brasky study concluded that “those with the highest levels of omega-3 fatty acids had a 43% higher risk of developing prostate cancer, and a 71% higher chance of developing high-grade prostate cancer, which is more likely to be fatal.”[ii] However, it was not clear from the study whether those studied derived their higher omega-3 blood levels from eating fish or taking supplements.
Publication of the Brasky study elicited responses from authors like Dr. Anthony D’Amico (Harvard Medical School) who pointed out numerous flaws in the way the data had been set up and analyzed.[iii] Since then, a number of other studies have pursued the relationship between fish oil and prostate cancer, and whether the effects are beneficial. The outlook is more optimistic than that suggested by the Brasky paper.
A study released a year after Brasky’s work was the result of research by a Quebec team on 48 patients diagnosed with low-risk prostate cancer who were on active surveillance (AS).[iv] None of the men had received treatment. The researchers reasoned that levels of omega-3 and other fatty acids within the prostate tissue would give better information that blood levels alone. Six months following their original biopsy, the men were again biopsied, and if their cancer had progressed from Gleason 6 to Gleason 7, their tissue samples were analyzed for various omega-3s. The team found that rather than promoting increased progression, omega-3 fatty acids were associated with a protective cellular function against progression.
Researchers from the University of Rochester (NY) reviewed results of the National Health and Examination Study from 2003-2010, and their results were published in October, 2014.[v] Drawing from data on 6018 men, they correlated blood levels of omega-3 fatty acids (from consumption of fish, not fish oil supplements) with PSA levels. They found no connection between the two, perhaps suggesting that fish consumption does not increase prostate cancer risk. A month later, a German study found no clear evidence that consuming omega-3s lowered the incidence of prostate cancer within a population; however, they did conclude that the intake of omega-3s “considerably reduces the risk of metastasis and PCa-related mortality.”[vi]
Finally, the most recent study to weigh in on the matter comes from Washington State University.[vii] Rather than a population-based study, the authors examined the biological effects of omega-3s on cellular mechanisms. Their laboratory results were encouraging; the team reports that three specific omega-3 lipids activate “signaling events that can inhibit growth factor-induced signaling, providing a novel mechanism for suppression of cancer cell proliferation.” In other words, the potential exists for consumption of omega-3 fatty acids to discourage the growth and progression of prostate cancer.
It is important to remember that eating fish delivers omega-3s in a more natural way than isolating them in a supplement. A paper out of Warsaw, Poland points out, “The way of processing and preservation of the fish, and other factors not included in previous studies, could have some importance in the etiology [origin within an individual] of this disease.”[viii] Omega-3s oxidize (break down) naturally, and exposure to high-heat cooking or processing fish by smoking will contribute to the formation of compounds with possibly carcinogenic effects, including the development of prostate cancer. The authors emphasize the importance of consuming only quality fish and fish oil, as contaminant-free as possible since environmental pollutants found in fish may also be carcinogenic.
It is impossible to compare the studies summarized above on an apples-to-apples basis, but the evidence suggests that prostate cancer patients who either consume quality fresh fish high in omega-3s or fish oil supplement stand to benefit on many levels, including reduced risk of prostate cancer spread. While more study is necessary at both the demographic and biological levels, it is reasonable to take heart from the work of all these authors.
[i] Brasky TM, Darke AK, Song X, Tangen CM et al. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J Natl Cancer Inst. 2013 Aug 7;105(15):1132-41. doi: 10.1093/jnci/djt174. Epub 2013 Jul 10.
[ii] Simon, Stacy. Omega-3 Fatty Acids Linked to Increase in Prostate Cancer Risk. American Cancer Society. July 17, 2013.
[iii] Ruth, Allan. Not just industry slamming omega-3-prostate links. July 15, 2013. http://www.nutraingredients.com/Research/Not-just-industry-slamming-omega-3-prostate-cancer-links
[iv] Moreel X, Allaire J, Léger C, Caron A et al. Prostatic and dietary omega-3 fatty acids and prostate cancer progression during active surveillance. Cancer Prev Res (Phila). 2014 Jul;7(7):766-76. doi: 10.1158/1940-6207.CAPR-13-0349. Epub 2014 May 13.
[v] Patel D, Thevenet-Morrison K, van Wijngaarden E. Omega-3 polyunsaturated fatty acid intake through fish consumption and prostate specific antigen level: results from the 2003 to 2010 National Health and Examination Survey.
Prostaglandins Leukot Essent Fatty Acids. 2014 Oct;91(4):155-60. doi: 10.1016/j.plefa.2014.07.008. Epub 2014 Jul 24.
[vii] Liu Z, Hopkins MM, Zhang Z, Quisenberry CB, Fix LC et al. Omega-3 fatty acids and other FFA4 agonists inhibit growth factor signaling in human prostate cancer cells. J Pharmacol Exp Ther. 2014 Dec 9. pii: jpet.114.218974. [Epub ahead of print]