Omega-3 fatty acids don't cut risk of heart disease?

For those who have experienced at least one heart attack, taking Omega-3 fatty acids may not help reduce risk of additional cardiovascular events such as myocardial infarction or heart attack, a new study presented at the European Society of Cardiology Congress 2010 held in Stockholm, Sweden from Aug 28 through Sept 1 suggests. 

Be warned, however, that the study, led by Daan Kromhout and colleagues from Wageningen University in the Netherlands, does not seem to provide a definite conclusion that use of omega-3 fatty acids are useless in patients who have suffered myocardial infarction, as many variables were present during the study. 

The researchers noted that a recent meta-analysis of randomized controlled trials of fish oil supplements with at least one gram per day of the omega-3 fatty acids known as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) reduced cardiac mortality in cardiac patients by 20 percent.

They also noted that low doses of these omega-3 fatty acids improved heart membrane composition and helped prevent cardiac arrhythmia, particularly ventricular fibrillation.

EPA and DHA are found high in oily fish like salmon, herring and sardine.  Omega-3 fatty acid  alpha-linolenic acid (ALA) is found in vegetables, seeds and nuts including soybeans, flax seeds and walnuts. 

In the current study, the researchers tested if a low dose of EPA and DHA, or ALA can reduce the risk of major cardiovascular events, fatal coronary heart disease and clinical sequelae of ventricular fibrillation. 

For the study, Kromhout and colleagues enlisted 4,837 patients aged 60 to 80 who had suffered myocardial infarction, or heart attacks.  Four groups of subjects were assigned 400 miligram per day of EPA and DHA or EPA and DHA along with two grams of ALA or a placebo spiked in about 20 grams of margarine produced by Unilever for 40 months. 

During the follow-up, 671 patients experienced a major cardiovascular event. The risk of cardiovascular events was not reduced in patients who received omega-3 fatty acids compared with those who received the placebo. 

However, ALA seemed to cut the risk of cardiovascular events like myocardial infarction in women by 27 percent and DPA and DHA seemed to cut the risk of coronary heart disease mortality in patients with diabetes. 

In patients with diabetes, EPA and DHA were associated with a 49 percent reduced risk of ventricular arrhythmia-related events; ALA cut the risk by 61 percent. 

The researchers concluded that "low doses of n-3 fatty acids do not reduce major cardiovascular events except a possible beneficial effect of ALA in women," and "n-3 fatty acids may prevent ventricular arrhythmia-related events in diabetic patients." 

The study has a number of limitations. First, the study population was made up of 78 percent men and 22 percent women; this could have affected the outcome of the trial. Second, the overwhelming majority, or 74 percent, of the population used alcohol and 77 percent were obese or overweight.  Third, almost all patients were using antithromotic agents; 90 percent used antihypertensive drugs and 86 percent lipid modifying drugs like statins. Fourth, margarine per se may have had an impact on the outcome. 

Because of these facts and their possible implications, the trial results may not be applicable to American patients.  Another reason is simply because the study patients consumed three times as much fish when entering the study as their American counterparts - 15 grams per day versus about 4.58 a day for Americans. 

R. Scott Wright of the Mayo Clinic in Rochester, MN was cited by MedPage Today saying the trial was faulty, as the margarine encouraged patients to increase their intake of bread. Wright suggested that too much bread means too much weight gain; additionally, the high sodium content in bread may also boost blood pressure, both of which may have implications in regards to the study outcome. 

The authors of the study suggested, according to Medpage Today, that all medications or therapies may have resulted in an overwhelming reduction in cardiovascular risk, rendering the effect of omega-3 fatty acids added in margarine relatively insignificant. 

In response to the study presentation, Professor Luigi Tavazzi from S. Matteo University Hospital in Pavia, Italy commented that the dose of EPA and DHA used in the trial was less than half of the amount tested in previous trials that showed positive associations between omega-3 fatty acids and reduced risk of death from heart attack and stroke. He also suggested that the study population was too small to have a reliable conclusion. 

The trial results may be a surprise to Prof. Tavazzi, who seems to expect that EPA and DHA or even ALA reduce the risk of cardiovascular events. He cited a few major studies, shown below, as linking omega-3 fatty acids to the reduced heart risk. 

The DART trial demonstrated that consuming two portions of oily fish per week was correlated with a 29 percent reduced mortality among 1015 men, compared with those who did not consume oily fish. 

The GISSI-Prevenzione trial found supplementation of 850 mg per day of EPA and DHA as purified ethyl esters reduced risk risk of death, nonfatal heart attack or myocardial infarction, and stroke among 11,323 patients, who experienced a recent heart attack, during a 3.5-year follow-up.  The risk of sudden cardiac death was reduced by 45 percent among the subjects using the supplements. 

Another study known as the Japan EPA Lipid Intervention Study found taking 1.8 grams per day of EPA ethyl esters significantly reduced the risk of major cardiovascular events such as unstable angina, fatal or nonfatal myocardial infarction, sudden cardiac death and revascularization in 18,000 Japanese men and women who had high cholesterol and were on low-dose statins during a 4.6-year period. 

Margarine may contain high levels of trans fat, according to the Food and Drug Administration. Trans fat has been associated with increased risk of heart disease and Harvard University nutritionists and epidemiologists believed that trans fat is implicated in more than 100,000 cardiac deaths each year in the United States. 

Dr. Jan L Breslow at Rockefeller University in New York, New York wrote an excellent review on the therapeutic and protective effect of omega-3 fatty acid supplements on cardiovascular disease, which was published in the June 2006 issue of American Journal of Clinical Nutrition. 

According to the author, who claims he has no conflict of interest, the American Heart Association recommends that everyone eat oily fish twice a week and those with coronary heart disease take EPA plus DHA from oily fish or supplements at a dose of 1 gram per day. 

In addition to omega-3 fatty acid supplements, or fish oil, many other foods and nutrients may also help reduce their heart risk.  Beneficial foods and nutrients include vitamin K2, vitamin D, tea, tart cherries, whole grains, and walnuts. 

By David Liu and editing by Rachel Stockton