New York Times questioned fish oil's heart-protecting powers, inaccurately; New evidence review found that fish-rich diets cut the risk up to 21% 04/01/2015
Anahad O'Connor's misleading post – titled "Fish Oil Claims Not Supported by Research” – appeared in the Times' March 30 Well blog.
It's true that some – though by no means all – clinical trials have not found clear evidence that omega-3 fish oils reduce the risk of heart attacks.
Nor have all clinical trials found that fish oil reduces the risk of sudden cardiac death … the heart-rhythm-related event that accounts for half of all cardiac deaths.
But other trials – including some of the largest and best-designed – have clearly affirmed that omega-3 fish oil has heart-protective powers.
And most non-clinical studies link fishy diets to better heart health, as we report below (see "Evidence from lab and epidemiological studies strongly supports fish").
For that and other reasons, the headline on the Times' blog post is clearly and irresponsibly wrong.
Sadly, the author – and some of the doctors he quoted – paint a highly misleading picture of the total body of clinical and other evidence.
New York Times blog post distorted the evidence
The Times' post implied that the early, positive clinical trials are outweighed by negative ones published more recently.
In reality, the value of omega-3 fish oil for heart health is backed by very substantial clinical evidence, whose positive findings are not outweighed by the negative outcomes of other trials.
This explains why health agencies worldwide still recommend fish oil strongly to people who don't eat much fish, or who need extra omega-3s to help sick hearts.
For example, contrary to the Times' characterization, an evidence review by researchers at the Tufts Medical Center came to a positive conclusion:
"Most trials reported that fish oil significantly reduced all-cause mortality, myocardial infarction [heart attack], cardiac and sudden death, or stroke.” (Wang C et al. 2006)
That conclusion was later echoed by U.S. researchers who analyzed 11 high-quality clinical trials:
"Dietary supplementation with omega-3 fatty acids significantly reduced the risk of cardiovascular deaths, sudden cardiac death, all-cause mortality, and non-fatal cardiovascular events.” (Marik PE, Varon J et al. 2009)
More recently, Harvard researchers affirmed the heart benefits of omega-3 fish oil:
"A large body of evidence from experimental, clinical, and epidemiologic research has demonstrated the potential benefits of fish oil on cardiovascular health.” (Hu FB, Manson JE 2012)
Positive trials were downplayed by The New York Times
Chief among the large, positive clinical trials that have persuaded health authorities to endorse omega-3 fish oil supplements were two conducted in Italy:
- GISSI-HF involved patients with congestive heart failure
- GISSI-Prevenzione involved people who'd suffered a heart attack (myocardial infarction)
The GISSI trials found that fish oil supplements further reduced patients' risks for heart failure, stroke, second heart attacks, and sudden cardiac death triggered by irregular heart rhythms (Marchioli R et al. 2001; Gissi-HF Investigators et al. 2008).
As the trial's lead authors wrote in the European Heart Journal, "The results of GISSI-Prevenzione indicate that in patients who have had a myocardial infarction [heart attack], omega-3 supplements ... reduced long-term complications to a clinically important extent." (Marchioli R, Valagussa )
In fact, as they noted, the benefits of fish oil seen in the GISSI trial were comparable to those seen in a large clinical trial that tested a statin drug in heart patients, called the LIPID study.
Medical opinion on omega-3 fish oil was also influenced by a large, five-year Japanese trial called JELIS, which tested one of fish oil's two key omega-3 fats, called EPA.
The JELIS trial tested omega-3 EPA as an adjunct to statin drugs in 18,645 older women and men with coronary artery disease and/or risk factors for it (Yokoyama M et al. 2003; Saito Y et al. 2008).
The results showed that adding omega-3 EPA to statin therapy cut the rate of major coronary events (heart attack, stroke, death) by 19 percent, compared with the no-EPA control group, which took only their usual cardiac drugs.
And more recently, several controlled clinical trials showed that fish oil cut the risk of heart attacks and sudden cardiac death significantly, versus placebo pills.
For example, see Omega-3s Cut Heart Risks & Death Rates in Clinical Trial. As we reported there, 563 older Norwegian men who took fish oil for three years were 47 percent less likely to die from any cause, and 11 percent less likely to suffer an adverse cardiovascular event (heart attack, stroke, sudden cardiac death), compared to the placebo group.
Even when results are mixed, there are almost always positive findings, such as we reported in Does Fish Oil Really Help Hearts?. In that five-year trial among 12,513 people with cardiac risk factors, fish oil didn't reduce risk much among the men assigned to take it ... but the women who took fish oil were 18 percent less likely to die from heart-related causes.
This largely positive record explains why the American Heart Association and public health authorities worldwide still recommend eating fish (especially fatty, omega-3-rich species like tuna, salmon, and sardines) and/or taking fish oil supplements routinely.
Negative trials often suffer from shortcomings
Although some trials conducted since the GSSI and JELIS studies have found significant benefits from fish oil, some have not.
But disappointing trials often suffered from limitations or confounding factors that muddied the waters or led the researchers to erroneous conclusions:
- Trial was small or short.
- Omega-3 doses were fairly low.
- Participants already had heart disease*.
- Analysis of results failed to account for participants' omega-6 intakes**.
- Participants were taking cardiac drugs (e.g., statins) proven to reduce heart risks.
**Very few trials have taken into account the amounts of competing omega-6 fats the participants were consuming. When that's been done, it's been found that the high omega-6 intake typical of modern diets blunts the heart benefits of omega-3s from fish oil supplements (see Heart Risks Raised by Omega-6 Excess, Know Your Omega-3/6 Numbers, and America's Sickening Omega Fats Imbalance).
Evidence from lab and epidemiological studies strongly supports fish
The American Heart Association (AHA) advises everyone to eat two servings of fish per week.
And the heart group advises people diagnosed with heart disease to take 1000mg of supplemental omega-3 fish oil daily.
Their advice stems partly from epidemiological studies that compared people's diets and health status.
Epidemiological studies cannot prove a cause-effect relationship ... but scientists give them more weight when the results of most such studies align, and enjoy supportive lab evidence.
Fish-source omega-3s enjoy ample lab evidence of heart benefits, and a healthy majority of epidemiological studies link fish-rich diets to lower risks for heart disease and its adverse outcomes.
(We recently reported on a study that persuasively linked Japan's low heart disease rates to its people's fish-heavy diet … see Do Fishy Diets Drive Japan's Superior Heart Health?.)
The adverse cardiac health outcomes apparently deterred by fish-rich diets include stroke, heart failure, sudden cardiac death ... and the subject of a new epidemiological study, acute coronary syndrome.
Acute coronary syndrome (ACS) is an umbrella term covering any circumstance that suddenly blocks or severely constricts the heart's blood supply.
The two most common forms of ACS are heart attacks and unstable angina, which can kill heart tissue in amounts ranging from a few cells to a whole section of the heart.
Now, a recent evidence review affirms abundant prior evidence that fishy diets help prevent heart attacks, unstable angina, and other forms of ACS.
Canadian evidence review affirms the heart-guarding value of fish
Researchers from Canada's McGill University conducted a meta-analysis (critical review) of 19 epidemiological studies (Leung Yinko SS et al. 2014).
Each study they selected for the meta-analysis had looked for links between fish consumption and the risk for heart attack, unstable angina, or other forms of ACS.
The Canadian team selected the 19 best epidemiological studies, which included 11 prospective-cohort and 8 case-control studies.
These studies involved a total of 408,305 healthy middle-aged people aged 47 to 62 – slightly more women (53 percent) than men – with no prior history of heart attack or other form of ACS.
Like some prior evidence reviews, their analysis found that fish consumption reduced ACS risk in a "dose-dependent” manner:
- Four or more servings per week reduced ACS risk by 21 percent.
- Every 100-gram-per-week increase in fish consumption reduced ACS risk by five percent.
Importantly, the analysis detected no gender or age differences, with the same levels of risk reduction seen in men and women of all ages in the range.
Omega-3s: Many reasons to get plenty
Diets high in omega-3-rich seafood appear to enhance or maintain people's brain health, metabolic health, eye health, and immune health, and help ensure optimal child development.
And they may extend people's lifespans and "health spans” … see High Omega-3 Levels Boost Longevity and Omega-3s' DNA-Telomere Effects vs. Heart Disease and Aging.
You can see and browse our hundreds of reports on omega-3 studies in our news archive ... look for the list of omega-3 health topics under "Omega-3 Fatty Acids” at the top right side of the archive page.
- American Heart Association (AHA). Acute Coronary Syndrome. Accessed at http://www.heart.org/HEARTORG/Conditions/HeartAttack/ AboutHeartAttacks/Acute-Coronary-Syndrome_UCM_428752_Article.jsp
- Belin RJ, Greenland P, Martin L, et al. Fish intake and the risk of incident heart failure: the Women's Health Initiative. Circ Heart Fail. 2011;4:404-413.
- Bucher HC, Hengstler P, Schindler C, Meier G. N-3 polyunsaturated fatty acids in coronary heart disease: a meta-analysis of randomized controlled trials. Am J Med. 2002 Mar;112(4):298-304.
- Casula M, Soranna D, Catapano AL, Corrao G. Long-term effect of high dose omega-3 fatty acid supplementation for secondary prevention of cardiovascular outcomes: A meta-analysis of randomized, placebo controlled trials [corrected]. Atheroscler Suppl. 2013 Aug;14(2):243-51. doi: 10.1016/S1567-5688(13)70005-9. Review. Erratum in: Atheroscler Suppl. 2014 Mar;233(1):122.
- Chen Q, Cheng LQ, Xiao TH, Zhang YX, Zhu M, Zhang R, Li K, Wang Y, Li Y. Effects of omega-3 fatty acid for sudden cardiac death prevention in patients with cardiovascular disease: a contemporary meta-analysis of randomized, controlled trials. Cardiovasc Drugs Ther. 2011 Jun;25(3):259-65. doi: 10.1007/s10557-011-6306-8.
- Chowdhury S, Ward H, Johnson L, Crowe F, Hu FB, Franco OH. Association between fish consumption, long chain omega 3 fatty acids, and risk of cerebrovascular disease: systematic review and meta-analysis. BMJ. 2012 Oct 30;345:e6698. doi: 10.1136/bmj.e6698. Review.
- Chowdhury R, Warnakula S, Kunutsor S, Crowe F, Ward HA, Johnson L, Franco OH, Butterworth AS, Forouhi NG, Thompson SG, Khaw KT, Mozaffarian D, Danesh J, Di Angelantonio E. Association of dietary, circulating, and supplement fatty acids with coronary risk: a systematic review and meta-analysis. Ann Intern Med. 2014 Mar 18;160(6):398-406. doi: 10.7326/M13-1788. Review. Erratum in: Ann Intern Med. 2014 May 6;160(9):658.
- Djoussé L, Akinkuolie AO, Wu JH, Ding EL, Gaziano JM. Fish consumption, omega-3 fatty acids and risk of heart failure: a meta-analysis. Clin Nutr. 2012;31:846-853.
- Enns JE, Yeganeh A, Zarychanski R, Abou-Setta AM, Friesen C, Zahradka P, Taylor CG. The impact of omega-3 polyunsaturated fatty acid supplementation on the incidence of cardiovascular events and complications in peripheral arterial disease: a systematic review and meta-analysis. BMC Cardiovasc Disord. 2014 May 31;14:70. doi: 10.1186/1471-2261-14-70. Review.
- He K, Song Y, Daviglus ML, Liu K, Van Horn L, Dyer AR, Goldbourt U, Greenland P. Fish consumption and incidence of stroke: a meta-analysis of cohort studies. Stroke. 2004 Jul;35(7):1538-42. Epub 2004 May 20.
- He K, Song Y, Daviglus ML, Liu K, Van Horn L, Dyer AR, Greenland P. Accumulated evidence on fish consumption and coronary heart disease mortality: a meta-analysis of cohort studies. Circulation. 2004 Jun 8;109(22):2705-11.
- Hu FB, Bronner L, Willett WC, Stampfer MJ, Rexrode KM, Albert CM, Hunter D, Manson JE. Fish and omega-3 fatty acid intake and risk of coronary heart disease in women. JAMA. 2002 Apr 10;287(14):1815-21.
- Iso H, Rexrode KM, Stampfer MJ, Manson JE, Colditz GA, Speizer FE, Hennekens CH, Willett WC. Intake of fish and omega-3 fatty acids and risk of stroke in women. JAMA. 2001 Jan 17;285(3):304-12.
- Khoueiry G, Abi Rafeh N, Sullivan E, Saiful F, Jaffery Z, Kenigsberg DN, Krishnan SC, Khanal S, Bekheit S, Kowalski M. Do omega-3 polyunsaturated fatty acids reduce risk of sudden cardiac death and ventricular arrhythmias? A meta-analysis of randomized trials. Heart Lung. 2013 Jul-Aug;42(4):251-6. doi: 10.1016/j.hrtlng.2013.03.006. Epub 2013 May 25.
- Kotwal S, Jun M, Sullivan D, Perkovic V, Neal B. Omega 3 Fatty acids and cardiovascular outcomes: systematic review and meta-analysis. Circ Cardiovasc Qual Outcomes. 2012 Nov;5(6):808-18. doi: 10.1161/CIRCOUTCOMES.112.966168. Epub 2012 Oct 30. Review. Kruse LG, Ogletree RL Jr. Omega-3 fatty acids and cardiovascular risk. J Miss State Med Assoc. 2013 Jun;54(6):156-7.
- Kwak SM, Myung SK, Lee YJ, Seo HG; Korean Meta-analysis Study Group. Efficacy of omega-3 fatty acid supplements (eicosapentaenoic acid and docosahexaenoic acid) in the secondary prevention of cardiovascular disease: a meta-analysis of randomized, double-blind, placebo-controlled trials. Arch Intern Med. 2012 May 14;172(9):686-94. doi: 10.1001/archinternmed.2012.262. Review.
- Larsson SC, Orsini N. Fish consumption and the risk of stroke: a dose-response meta-analysis. Stroke. 2011 Dec;42(12):3621-3. doi: 10.1161/STROKEAHA.111.630319. Epub 2011 Sep 8. Leung Yinko SS, Stark KD, Thanassoulis G, Pilote L. Fish consumption and acute coronary syndrome: a meta-analysis. Am J Med. 2014 Sep;127(9):848-57.e2. doi: 10.1016/j.amjmed.2014.04.016. Epub 2014 May 4.
- Li YH, Zhou CH, Pei HJ, Zhou XL, Li LH, Wu YJ, Hui RT. Fish consumption and incidence of heart failure: a meta-analysis of prospective cohort studies. Chin Med J (Engl). 2013 Mar;126(5):942-8. Marik PE, Varon J. Omega-3 dietary supplements and the risk of cardiovascular events: a systematic review. Clin Cardiol. 2009 Jul;32(7):365-72. doi: 10.1002/clc.20604. Review.
- The Long-Term Intervention with Pravastatin in Ischaemic Disease (LIPID) Study Group. Prevention of cardiovascular events and death with pravastatin in patients with coronary heart disease and a broad range of initial cholesterol levels. N Engl J Med 1998; 339: 1349–57.
- Marchioli R, Valagussa F. The results of the GISSI-Prevenzione trial in the general framework of secondary prevention. Eur Heart J. 2000 Jun;21(12):949-52. Review.
- Mozaffarian D, Lemaitre RN, Kuller LH, et al. Cardiac benefits of fish consumption may depend on the type of fish meal consumed: the Cardiovascular Health Study. Circulation. 2003;107:1372-1377.
- Mozaffarian D, Psaty BM, Rimm EB, et al. Fish intake and risk of incident atrial fibrillation. Circulation. 2004;110:368-373.
- Psota TL, Gebauer SK, Kris-Etherton P. Dietary omega-3 fatty acid intake and cardiovascular risk. Am J Cardiol. 2006 Aug 21;98(4A):3i-18i. Epub 2006 May 30. Review.
- Rizos EC, Ntzani EE, Bika E, Kostapanos MS, Elisaf MS. Association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events: a systematic review and meta-analysis. JAMA. 2012 Sep 12;308(10):1024-33. doi: 10.1001/2012.jama.11374. Review.
- Wang C, Harris WS, Chung M, Lichtenstein AH, Balk EM, Kupelnick B, Jordan HS, Lau J. n-3 Fatty acids from fish or fish-oil supplements, but not alpha-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review. Am J Clin Nutr. 2006 Jul;84(1):5-17. Review.
- Wen YT, Dai JH, Gao Q. Effects of Omega-3 fatty acid on major cardiovascular events and mortality in patients with coronary heart disease: a meta-analysis of randomized controlled trials. Nutr Metab Cardiovasc Dis. 2014 May;24(5):470-5. doi: 10.1016/j.numecd.2013.12.004. Epub 2013 Dec 25.
- Xun P, Qin B, Song Y, Nakamura Y, Kurth T, Yaemsiri S, Djousse L, He K. Fish consumption and risk of stroke and its subtypes: accumulative evidence from a meta-analysis of prospective cohort studies. Eur J Clin Nutr. 2012 Nov;66(11):1199-207. doi: 10.1038/ejcn.2012.133. Epub 2012 Oct 3.
- Zhao YT, Chen Q, Sun YX, Li XB, Zhang P, Xu Y, Guo JH. Prevention of sudden cardiac death with omega-3 fatty acids in patients with coronary heart disease: a meta-analysis of randomized controlled trials. Ann Med. 2009;41(4):301-10. doi: 10.1080/07853890802698834.
- Zheng J, Huang T, Yu Y, Hu X, Yang B, Li D. Fish consumption and CHD mortality: an updated meta-analysis of seventeen cohort studies. Public Health Nutr. 2012 Apr;15(4):725-37. doi: 10.1017/S1368980011002254. Epub 2011 Sep 14.