Study questions fish oil benefit before heart attack

Originally, the researchers had thought the main goal of their study would be to see how many people died or had a heart attack or stroke. But those events turned out to be less common than expected, probably because the patients “were rather intensively exposed to recommended preventive treatment (including healthy lifestyle habits) by their family physicians,” Roncaglioni said.

Thus, the goal of the study was modified to count anyone who died or was admitted to the hospital for a heart-related cause.

Certain factors did seem to improve slightly more in the fish oil recipients, such as levels of fat and “good” cholesterol in the blood.

But other measures such as “bad” cholesterol, blood pressure and blood sugar remained similar in the fish oil and olive oil groups, and there was no difference in the proportion of patients in the two groups who needed heart medications.

Benefit of fish oils for heart disease treatment or prevention
Fish oil supplements reduce the risk for heart disease by improving circulation, improving the function of the endothelium, the inner lining of arteries, reduce the risk of heart arrhythmias. Fish oils are rapidly incorporated into human heart cell phospholipids at the expense of arachidonic acid. This may lead to a reduction of arrhythmias or heart palpitations.

Benefit of fish oil to reduce the risk of sudden death
Increasing dietary omega-3 fatty acids from fish oils and decreasing omega-6 fatty acids, found in plant seed oils such as corn, safflower, and sunflower, is a way to reduce the risk of sudden death from irregular heart rhythms or heart attacks.
  One cause of sudden death is ventricular fibrillation, in which the heart contracts in a fast and chaotic rhythm that makes it unable to pump blood to the rest of the body. A number of factors including cigarette use, fasting, diabetes, hyperthyroidism or heart attack can trigger the release of fatty acids from adipose tissue.

  Fats that we eat are stored in adipose (fat) tissue. When these fats are released from their storage sites, they become free fatty acids. But not all fatty acids are equal in their propensity to cause arrhythmias. High levels of omega-6 fatty acids may encourage arrhythmias if their levels aren’t balanced by omega-3 fatty acids.

Fish oils reduce heart rhythm problems and palpitations
Daily supplementation with fish oils reduces heart rate variability. Heart rate variability measures the variability in the intervals between heartbeats, with lower variability being associated with higher risks of heart disease and death. A normal heart does not always have the same time intervals between beats, but every so often (in cycles) the interval between cardiac beats changes; i.e. a little shorter, or longer. How frequent these variations occur are a measure of the effect of the nervous regulation of the heart. A sick heart losses this fine tuning.

Roughly two of every 100 patients died of heart disease, regardless of which group they were in. And roughly 10 of every 100 patients in each group needed to be hospitalized for a heart-related problem.

By the end of the study, 18 percent had stopped taking their fish oil and 19 percent had stopped taking their olive oil. When those volunteers were excluded from the study, there was still no significant difference between the groups in the risk of death or hospitalization for heart problems.

The rates of gastrointestinal side effects, cancer and bleeding were comparable in the two groups.

The U.S. Food and Drug Administration says olive oil has heart benefits of its own. Is it possible that using olive oil as the placebo in this study skewed the results by protecting the placebo group to some extent? Roncaglioni doesn’t think so.

She said giving olive oil as a placebo probably did not bring down the overall rate of heart problems in that group because “one gram of olive oil corresponds to only 1/30th of the mean amount consumed in the Mediterranean diet,” which would make it of very small benefit.

SOURCE: New England Journal of Medicine, online May 8, 2013


n–3 Fatty Acids in Patients with Multiple Cardiovascular Risk Factors

The Risk and Prevention Study Collaborative Group

The Risk and Prevention Study tested the hypothesis that n−3 fatty acids, which have been shown to be beneficial in patients who have had a myocardial infarction (in the Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto Miocardico [GISSI]–Prevenzione study) or heart failure (in the GISSI Heart Failure [GISSI-HF] study), would be effective in reducing cardiovascular risk among patients who were treated according to the standard of care and who had multiple cardiovascular risk factors or atherosclerotic disease but no previous myocardial infarction. Our findings provide no evidence of the usefulness of n−3 fatty acids for preventing cardiovascular death or disease in this population.

The consistently null effect across the various end points and subgroups does not suggest alternative interpretations, but a few epidemiologic observations are useful. The overall frequency of hard end points (particularly the rates of sudden death from cardiac causes and death from coronary causes), on which n−3 fatty acids showed a clear benefit in the GISSI–Prevenzione study, was substantially lower than expected, possibly reflecting a country-specific low cardiovascular-risk profile (particularly with regard to dietary habits) and the rather intensive exposure of our study population to preventive treatments with further improvement during the 5-year follow-up period. Death from cardiovascular causes at 5 years made up only 18.7% of the primary composite end point. In addition, hospital admissions for cardiovascular causes were concentrated among patients 65 years of age or older and were rarely predictive of death: only 7.7% of patients admitted to the hospital for a cardiovascular cause died from cardiovascular causes during the trial.

The only two significant results (a reduction in hospital admissions for heart failure with n−3 fatty acids and their preventive effect in women) must be considered conservatively. Both may be due to chance, although they are consistent with two findings from other studies: the beneficial effect of n−3 fatty acids in patients with heart failure in the GISSI-HF study and the decrease in nonfatal coronary events in patients with hypercholesterolemia, the majority of whom were women, in the Japan Eicosapentaenoic Acid Lipid Intervention Study (JELIS). Our results are more consistent with the null findings of the Outcome Reduction with an Initial Glargine Intervention (ORIGIN) trial, which tested supplementation with n−3 fatty acids in patients with dysglycemia.
N Engl J Med 2013; 368:1800-1808May 9, 2013DOI: 10.1056/NEJMoa1205409

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