The news was reported online July 10, 2013 that the results of a large study, over 2000 men, the SELECT  (Selenium and Vitamin E Cancer Prevention Trial) was showing that high levels of each of several fatty acids (EPA and DHA) from fish were associated with an increased Prostate Cancer risk. Theodore M. Brasky, PhD, of the Ohio State University Comprehensive Cancer Center in Columbus reported online in Journal of the National Cancer that high levels of EPA were associated with an increased risk of low-grade Prostate Cancer. High levels of DPA and DHA were associated with an increased risk of low-grade and total Prostate Cancer.

Similar findings had been published by the same author in 2011 in American Journal of Epidemiology.  That study examined data from men enrolled in the Prostate Cancer Prevention Trial. Compared with men in the lowest quartile of serum DHA, those in the highest quartile had a 2.5 times increased risk of high-grade Prostate

However, on reviewing the literature, I was able to find at least 20 studies that showed the opposite, that fish oil actually lowered the incidence  of Prostate Cancer, that it reduced tumor weight in mice, that it caused growth arrest of Prostate Cancer cell lines, that it was strongly associated with a decrease in aggressive Prostate Cancer incidence, that it improved Prostate cancer survival, and that it sensitized tumor tissue to chemotherapy drugs.  A sampling of these studies is at the end of this article.

But how do we reconcile these 2 studies with the 20 others with opposite findings?

First of all, all fish oils are not alike.  In my medical nutrition practice, I am constantly educating people about the need to consume only ultra-refined fish oil. Ultra-refined is Pharmaceutical grade fish oil that is concentrated, and purified to remove the mercury and the PCBs.  This is more expensive but well worth it.  There is no other way to get the anti-inflammatory effects of fish oil without polluting your body with PCBs.

Farmed Salmon has the highest amount of PCBs of any other food, according to references from EPA 2000, and USDA  2002, And fish oil, made from farmed salmon, is even worse because the contaminants are concentrated.  See chart:

According to EFSA Journal 2010,8(7):1701 Scientific Report of EFSA-Results of the monitoring of non dioxin-like PCBs in food and feed European Food Safety Authority,

Fish and fish products oil are the most contaminated foods that can be consumed!
mcg/kg  PCB
Fish liver                             148
Fish oil                                  59
Fish meat                              23
Dairy inc. butter                   16.7
Meat -beef/poultry/pork        8.7 mcg/kg fat
Plant foods                            0.08 mcg/kg

The highest mean contamination level was observed in fish and fish derived products followed by eggs, milk and their products, meat and their products. You can see by this chart that fish oil is more than twice as toxic as the fish itself.

Does anybody think this could be a confounding variable in this study?  PCBs have been found to be a risk factor for Prostate Cancer, Journal of Occupational & Environmental Medicine:   July 2003 – Volume 45 – Issue 7 – pp 692-702  Organochlorines and Risk of Prostate Cancer.

Is it possible that 2 different kinds of fish oil were being consumed to account for the differing results?

Nobody mentions in these studies what kind of fish oil these subjects were taking, but the cheap, toxic kind of fish oil is what is generally sold and consumed in this country.  The studies showing benefit (below) were administering the fish oil to their subjects to study their effects. Therefore they possibly were more likely to use pharmaceutical grade fish oil.
In the 2 studies associated with Prostate Cancer (mentioned above) fish oil levels were incidentally measured but the study was actually about Vitamin E and Selenium and not about fish oil at all. The fish oil was purchased by the consumer in these studies and more likely to be the toxic kind.  Granted, high doses of fish oil can create immunosuppressive effects in some people, but If one is really looking for the mechanism for fish oil’s effect on Prostate cancer incidence, one need look no further than the toxic load that comes in with the fish oil.


Prostate. 2011 Sep 15;71(13), Cavazos DA, et al.,  Department of Nutritional Sciences, The University of Texas at Austin.  DHA selectively sensitizes prostate cancer cells to growth arrest.

Asian Pac J Cancer Prev. 2011;12(12):3331-4. Saw CL, et al. The Fish Oil group had significantly reduced prostate tumor weight (p<0.05) compared to the HF group. The incidence of palpable tumors and carcinomas was also lowered. Finally, there was no metastasis found in the Fish Oil group, whereas in the HF group, 16.7% of the mice were found to have metastases.

J Surg Res. 2011 Jan;165(1):75-81.. Strouch MJ  Department of Surgery, Feinberg School of Medicine, Northwestern University, A high ω-3 fat diet mitigates pancreatic precancer by inhibition of cellular proliferation through induction of cell cycle arrest and apoptosis.

Nutr Cancer. 2011;63(5):771-7Friedrichs W, et al. Department of Medicine, University of Texas Health Science Center at San Antonio  The omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were able to prevent progression of LNCaP cells while the omega-6 fatty acid arachidonic acid (AA) actually promoted cell growth under conditions of hormone depletion.

PLoS One. 2012;7(9):  O’Flaherty JT, et. Al.  Department of Internal Medicine Wake Forest School of Medicine, Winston-Salem, NCThe DHA metabolites thus slow prostate cancer cell proliferation by engaging the PPARγ/syndecan-1 pathway of apoptosis and thereby may contribute to the prostate cancer-suppressing effects of not only 15-LOX but also dietary DHA.

Carcinogenesis. 2012 Jan;33(1):140-8.  Akinsete JA, et. Al.  Department of Biochemistry and Microbiology, Marshall University School of Medicine, Huntington, WV Our results suggest that consumption of high ω-3 diet slows down prostate tumorigenesis by lowering estradiol, testosterone and AR levels, promoting apoptosis and suppressing cell proliferation in C3(1)Tag mice.

Drug News Perspect. 2008 Nov;21(9):504-10.  Pauwels EKKairemo K.  Pisa University Medical School, Pisa, Italy.Without exception, these publications demonstrate that higher EPA (and possibly DHA) concentrations in the cell membrane, a validated measure for plasma fatty acids, is associated with lower cancer risk. These intriguing results are confirmed by the recently published huge European Prospective Investigation into cancer and nutrition (N = 478,040 men and women) and U.S.-based Physicians Health Study (N = 22,071 men). These studies have unequivocally confirmed that fish intake has a favorable effect on cancer risk.

Clin Cancer Res. 2009 Apr 1;15(7):2559-66.   Fradet V, Departments of Urology, Institute for Human Genetics, University of California at San Francisco, San Francisco, California.
Increasing intake of LC n-3 (Long chain omega 3) was strongly associated with a decreased risk of aggressive prostate cancer.  Dietary LC n-3 polyunsaturated fatty acids appear protective for aggressive prostate cancer.

Eur J Cancer. 2009 Aug;45(12):2077-86. Spencer LMann , et. Al.
Department of HPB and Pancreatic Surgery, Leicester General Hospital.
Omega-3 fatty acid (omega-3 FA) consumption has long been associated with a lower incidence of colon, breast and prostate cancers in many human populations. The conclusions drawn from this review suggest that omega-3 FAs in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) found principally in oily fish have potent anti-angiogenic action.

PLoS One. 2013 Apr 17;8(4)  Torfadottir JE, Centre of Public Health Sciences, University of Iceland, Reykjavik, Iceland. ….whereas fish oil consumption may be protective against progression of prostate cancer in elderly men. In a setting with very high fish consumption, no association was found between overall fish consumption in early or midlife and prostate cancer risk.

Am J Clin Nutr. 2012 Apr;95(4):944-50.  Touvier M, et. Al.,  National Institute of Health and Medical Research, Paris. These findings suggest that n-3 PUFA intake may counteract the procarcinogenic actions of sICAM-1.

Br J Pharmacol. 2009 Feb;156(3):420-31 Nakajima TKubota Net. Al.,  T   Department of Ischemic Circulatory Physiology, The University of Tokyo, Japan. Treatment with EPA inhibited I(Na) directly and also indirectly, by down-regulation of Na(v) mRNA expression in prostate cancer cells, thus inhibiting their metastatic potential.

Carcinogenesis. 2012 Feb;33(2):404-12.  Wang SWu J, et. Al.,  Department of Cancer Biology, Wake Forest University School of Medicine, Winston-Salem, NC. Dietary omega-3 PUFA supplementation in conjunction with androgen ablation may significantly delay the development of castration-resistant prostate cancer in patients compared with androgen ablation alone.

Cancer Prev Res (Phila). 2011 Dec;4(12):2062-71  Aronson WJ,  et al.,  Department of Urology, School of Medicine, University of California-Los Angeles The intervention resulted in decreased prostate cancer proliferation and decreased prostate tissue omega-6:omega-3 ratios. These results support further studies evaluating reduction of dietary fat with fish oil supplementation on modulating prostate cancer biology.

Cancer Treat Rev. 2013 Aug;39(5):473-88.   Hajjaji NBougnoux P. Cancer Research Laboratory, University Hospital of Tours, France. Marine-derived lipids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have the potential to differentially sensitize tissues to chemotherapy. These lipids enhance the cytotoxicity of 15 anticancer drugs . However, DHA and EPA do not sensitize non-tumor tissues to anticancer drugs,

Am J Clin Nutr. 2008 Nov;88(5):1297-303. Chavarro JE,  et al.,  Department of Nutrition, Harvard School of Public Health, Boston, MA   These results suggest that fish intake is unrelated to prostate cancer incidence but may improve prostate cancer survival.

Am J Clin Nutr. 2010 Nov;92(5):1223-33. Szymanski KM,  et al.,  Division of Urology, McGill University Health Centre, Montreal, Canada.
Our meta analyses showed a significant 63% reduction in prostate cancer-specific mortality.

Am J Epidemiol. 2012 Aug 1;176(3):240-52.Epstein M, et al.,   This study suggests that high intake of total fat and certain saturated fatty acids may worsen prostate cancer survival, particularly among men with localized disease. In contrast, high marine omega-3 fatty acid intake may improve disease-specific survival for all men.

Carcinogenesis. 2013 Jan;34(1):176-82.  Hu Y,  et al.,  Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, NC Our previous studies have shown that the n-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) induces apoptosis in human prostate cancer cells