Fish and fish oil consumption do not appear to protect against heart disease, arrhythmias, or sudden death, but why would they increase cancer risk?
Omega 3s, Prostate Cancer, and Atrial Fibrillation
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2013 was a bad year for fish oil. Claims were crushed that the long chain omega-3s in fish oil, EPA, and DHA would stop the progression of heart disease. And then, DHA was associated with increased risk of prostate cancer and monumentally failed to treat macular degeneration. This over-the-top rhetoric sounded a little suspicious, and indeed, the paper was retracted because the author sells some rival supplement that he failed to disclose. But, he does have a point.
I covered the fish oil failure for heart disease. What about the increased cancer risk? Men with the highest circulating levels in their blood of the long chain omega-3 fat DHA were found to be at higher risk for prostate cancer. Though, a subsequent compilation of all such studies suggested EPA, the other major long chain omega-3 in fish and fish oil, may be more closely associated with increased cancer risk. Either way, these long chain omega-3s have been promoted for prevention of heart disease and cancer.
But now, we know that not only does there appear to be no benefit for death, heart attack, or stroke, but there may be an elevation in cancer risk. The general recommendations to increase the intake of these fats should consider its potential risks.
How could eating more fish or fish oil increase cancer risk? Well, there are some industrial pollutants, like PCBs, linked to increased prostate cancer risk, and the primary source of exposure in the general population is believed to be through diet: from fish, meat, and dairy products. If you do a supermarket survey, the PCBs, shown in white here, are highest in freshwater fish, and lowest in vegans—cannibals take note! No, that’s just how they label the market basket of plant foods, though vegans have been tested, and they were found to be significantly less polluted, including the PCB linked to prostate cancer.
But, this study was done in North America where people don’t eat a lot of fish. And indeed, even the group with the highest DHA levels weren’t that high. And so, maybe the confounding factor was meat consumption in general, not just fish. And, lower meat consumption may be a reason for the lower rates of prostate cancer in the lower DHA group, as the consumption of well-done meat is associated with an increased risk of prostate cancer, and intake should be restricted.
We also used to think omega-3s could protect us from arrhythmias (abnormal heart rhythms), like atrial fibrillation. Millions suffer from the condition, which causes an irregular heartbeat and a higher risk of stroke and death, but fish and fish oil consumption does not appear effective for preventing it or treating it.
Other arrhythmias can be life-threatening and cause sudden death. Despite initial encouraging results, in more recent studies, fish and fish oil consumption have not only failed to reduce sudden cardiac death with omega-3s, but actually increased mortality in cardiac patients. For example, men with heart disease, advised to eat more oily fish, or supplied with fish oil capsules, were found to have a higher risk of cardiac death—maybe because of the contaminants in fish, such as mercury?
In either case, given the inconsistent benefits and the potential adverse effects, omega-3s must be prescribed with caution, and generalized recommendations to increase fish intake or to take fish oil capsules need to be reconsidered.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.
- G E Billman. The effects of omega-3 polyunsaturated fatty acids on cardiac rhythm: a critical reassessment. Pharmacol Ther. 2013 Oct;140(1):53-80.
- O Khawaja, J M Gaziano, L Djousse. A meta-analysis of omega-3 fatty acids and incidence of atrial fibrillation. J Am Coll Nutr. 2012 Feb;31(1):4-13.
- B S Peskin. Why fish oil fails: a comprehensive 21st century lipids-based physiologic analysis. J Lipids. 2014;2014:495761.
- B S Peskin. Why fish oil fails: a comprehensive 21st century lipids-based physiologic analysis. J Lipids. 2014;2014:495761.
- B S Peskin. Retracted: Why Fish Oil Fails: A Comprehensive 21st Century Lipids-Based Physiologic Analysis. Journal of Lipids 4 November 2014.
- T M Brasky, A K Darke, X Song, C M Tangen, P J Goodman, I M Thompson, F L Meyskens Jr, G E Goodman, L M Minasian, H L Parns, E A Klein, A R Kristal. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J Natl Cancer Inst. 2013 Aug 7;105(15):1132-41.
- F L Crowe, P N Appleby, R C Travis, M Barnett, T M Brasky, H B Bueno=de-Mesquita, V Chajes, J E Chavarro, M D Chirlaque, and more. Circulating fatty acids and prostate cancer risk: individual participant meta-analysis of prospective studies. J Natl Cancer Inst. 2014 Sep 10;106(9).
- A Schecter, P Cramer, K Boggess, J Stanley, J R Olson. Levels of dioxins, dibenzofurans, PCB and DDE congeners in pooled food samples collected in 1995 at supermarkets across the United States. Chemosphere. 1997 Mar-Apr;34(5-7):1437-47.
- J M Ritchie, S L Vial, L J Fuortes, H Guo, V E Reedy, E M Smith. Organochlorines and risk of prostate cancer. J Occup Environ Med. 2003 Jul;45(7):692-702.
- H Arguin, M Sanchez, G A Bray, J C Lovejoy, J C Peters, R J Jandacek, J P Chaput, A Tremblay. Impact of adopting a vegan diet or an olestra supplementation on plasma organochlorine concentrations: results from two pilot studies. Br J Nutr. 2010 May;103(10):1433-41.
- M F McCarty, J J Dinicolantonio, C J Lavie, J H O’Keefe. RE: Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J Natl Cancer Inst. 2014 Apr;106(4):dju014.
- D Mandair, R E Rossi, M Pericleous, T Whyand, M E Caplin. Prostate cancer and the influence of dietary factors and supplements: a systematic review. Nutr Metab (Lond). 2014 Jun 16;11:30.
- M L Burrn, P A Ashfield-Watt, F D Dunstan, A M Fehily, P Breay, T Ashton, P C Zotos, N A Haboubi, P C Elwood. Lack of benefit of dietary advice to men with angina: results of a controlled trial. Eur J Clin Nutr. 2003 Feb;57(2):193-200.
Images thanks to Survivor via Pixabay.
2013 was a bad year for fish oil. Claims were crushed that the long chain omega-3s in fish oil, EPA, and DHA would stop the progression of heart disease. And then, DHA was associated with increased risk of prostate cancer and monumentally failed to treat macular degeneration. This over-the-top rhetoric sounded a little suspicious, and indeed, the paper was retracted because the author sells some rival supplement that he failed to disclose. But, he does have a point.
I covered the fish oil failure for heart disease. What about the increased cancer risk? Men with the highest circulating levels in their blood of the long chain omega-3 fat DHA were found to be at higher risk for prostate cancer. Though, a subsequent compilation of all such studies suggested EPA, the other major long chain omega-3 in fish and fish oil, may be more closely associated with increased cancer risk. Either way, these long chain omega-3s have been promoted for prevention of heart disease and cancer.
But now, we know that not only does there appear to be no benefit for death, heart attack, or stroke, but there may be an elevation in cancer risk. The general recommendations to increase the intake of these fats should consider its potential risks.
How could eating more fish or fish oil increase cancer risk? Well, there are some industrial pollutants, like PCBs, linked to increased prostate cancer risk, and the primary source of exposure in the general population is believed to be through diet: from fish, meat, and dairy products. If you do a supermarket survey, the PCBs, shown in white here, are highest in freshwater fish, and lowest in vegans—cannibals take note! No, that’s just how they label the market basket of plant foods, though vegans have been tested, and they were found to be significantly less polluted, including the PCB linked to prostate cancer.
But, this study was done in North America where people don’t eat a lot of fish. And indeed, even the group with the highest DHA levels weren’t that high. And so, maybe the confounding factor was meat consumption in general, not just fish. And, lower meat consumption may be a reason for the lower rates of prostate cancer in the lower DHA group, as the consumption of well-done meat is associated with an increased risk of prostate cancer, and intake should be restricted.
We also used to think omega-3s could protect us from arrhythmias (abnormal heart rhythms), like atrial fibrillation. Millions suffer from the condition, which causes an irregular heartbeat and a higher risk of stroke and death, but fish and fish oil consumption does not appear effective for preventing it or treating it.
Other arrhythmias can be life-threatening and cause sudden death. Despite initial encouraging results, in more recent studies, fish and fish oil consumption have not only failed to reduce sudden cardiac death with omega-3s, but actually increased mortality in cardiac patients. For example, men with heart disease, advised to eat more oily fish, or supplied with fish oil capsules, were found to have a higher risk of cardiac death—maybe because of the contaminants in fish, such as mercury?
In either case, given the inconsistent benefits and the potential adverse effects, omega-3s must be prescribed with caution, and generalized recommendations to increase fish intake or to take fish oil capsules need to be reconsidered.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.
- G E Billman. The effects of omega-3 polyunsaturated fatty acids on cardiac rhythm: a critical reassessment. Pharmacol Ther. 2013 Oct;140(1):53-80.
- O Khawaja, J M Gaziano, L Djousse. A meta-analysis of omega-3 fatty acids and incidence of atrial fibrillation. J Am Coll Nutr. 2012 Feb;31(1):4-13.
- B S Peskin. Why fish oil fails: a comprehensive 21st century lipids-based physiologic analysis. J Lipids. 2014;2014:495761.
- B S Peskin. Why fish oil fails: a comprehensive 21st century lipids-based physiologic analysis. J Lipids. 2014;2014:495761.
- B S Peskin. Retracted: Why Fish Oil Fails: A Comprehensive 21st Century Lipids-Based Physiologic Analysis. Journal of Lipids 4 November 2014.
- T M Brasky, A K Darke, X Song, C M Tangen, P J Goodman, I M Thompson, F L Meyskens Jr, G E Goodman, L M Minasian, H L Parns, E A Klein, A R Kristal. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J Natl Cancer Inst. 2013 Aug 7;105(15):1132-41.
- F L Crowe, P N Appleby, R C Travis, M Barnett, T M Brasky, H B Bueno=de-Mesquita, V Chajes, J E Chavarro, M D Chirlaque, and more. Circulating fatty acids and prostate cancer risk: individual participant meta-analysis of prospective studies. J Natl Cancer Inst. 2014 Sep 10;106(9).
- A Schecter, P Cramer, K Boggess, J Stanley, J R Olson. Levels of dioxins, dibenzofurans, PCB and DDE congeners in pooled food samples collected in 1995 at supermarkets across the United States. Chemosphere. 1997 Mar-Apr;34(5-7):1437-47.
- J M Ritchie, S L Vial, L J Fuortes, H Guo, V E Reedy, E M Smith. Organochlorines and risk of prostate cancer. J Occup Environ Med. 2003 Jul;45(7):692-702.
- H Arguin, M Sanchez, G A Bray, J C Lovejoy, J C Peters, R J Jandacek, J P Chaput, A Tremblay. Impact of adopting a vegan diet or an olestra supplementation on plasma organochlorine concentrations: results from two pilot studies. Br J Nutr. 2010 May;103(10):1433-41.
- M F McCarty, J J Dinicolantonio, C J Lavie, J H O’Keefe. RE: Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. J Natl Cancer Inst. 2014 Apr;106(4):dju014.
- D Mandair, R E Rossi, M Pericleous, T Whyand, M E Caplin. Prostate cancer and the influence of dietary factors and supplements: a systematic review. Nutr Metab (Lond). 2014 Jun 16;11:30.
- M L Burrn, P A Ashfield-Watt, F D Dunstan, A M Fehily, P Breay, T Ashton, P C Zotos, N A Haboubi, P C Elwood. Lack of benefit of dietary advice to men with angina: results of a controlled trial. Eur J Clin Nutr. 2003 Feb;57(2):193-200.
Images thanks to Survivor via Pixabay.
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Title
Omega 3s, Prostate Cancer, and Atrial Fibrillation
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
Fish oil doesn’t help with heart disease?! I was as surprised as you. See: Is Fish Oil Just Snake Oil?
In terms of PCB contamination, see Food Sources of PCB Chemical Pollutants and PCBs in Children’s Fish Oil Supplements. Our oceans and waterways have become humanity’s sewer—everything eventually flows into the sea. For discussion of all the other industrial contaminants that build up in the aquatic food chain, see:
- Food Sources of Flame-Retardant Chemicals
- Food Sources of Perfluorochemicals
- Fish and Diabetes
- Diabetes and Dioxins
- Pollutants in Salmon and Our Own Fat
- Dioxins in U.S. Farm-Raised Catfish
- Dietary Pollutants May Affect Testosterone Levels
- Flame-Retardant Pollutants and Child Development
- Fish Consumption and Suicide
- How Long to Detox from Fish Before Pregnancy
For ways to decrease the risk of prostate cancer and slow its progression, see:
- Ex Vivo Cancer Proliferation Bioassay
- Prostate Cancer and Organic Milk vs. Almond Milk
- Flaxseed vs. Prostate Cancer
- Eggs, Choline, and Cancer
- Prostate Cancer Survival: The A/V Ratio
In 2022, I put up a new video on Afib. See The Best Diet for Treating Atrial Fibrillation.
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