When it comes to heart-healthy foods, those containing omega-3 fatty acids are high on the recommended list. But new research shows that the beneficial fats, found in certain types of fish and plants, may not help reduce heart attacks as much as previously thought.
Researchers in the Netherlands report that among heart-attack survivors, those who boosted their omega-3 intake had the same risk of a second heart attack as those who did not supplement their diet with added omega-3s. The study involved 4,837 men and women who were being treated for heart disease with medications ranging from cholesterol-lowering statins to antihypertension drugs. The members of the experimental group, who ate about four teaspoons of omega-3-enriched margarine a day (which provided them with an additional 400 mg of the fats daily) for more than three years, did not experience any fewer heart events than patients in the placebo group who ate unadulterated margarine.
The findings, published online by the New England Journal of Medicine, surprised heart experts, who had expected that increasing omega-3 intake would translate to fewer second heart attacks. The unsaturated fats — which can lower triglyceride levels and reduce the buildup of atherosclerotic plaques, which contribute to heart attacks — are known to be a heart-healthy substitute for animal fats in meat, dairy and butter.
But the authors point out that their study volunteers were already being properly treated following their initial heart attack — about 85% of the volunteers were taking statins to lower their cholesterol and many also relied on medications to control their blood pressure. These powerful therapies may have put the patients at a low risk of a secondary event to begin with, and the study's three-year follow-up simply may not have been long enough to capture any additional reduction in heart-related problems or deaths attributable to omega-3s.
The study's lead author, Professor Daan Kromhout of Wageningen University, says the benefits of the fats may become more obvious in certain subgroups of patients, such as those with diabetes or others who are at increased risk of heart disease but are not as well treated as the volunteers in this study.
The results should not discourage people from substituting omega-3 fats for animal fats when they can, says Alice Lichtenstein, professor of nutrition, science and policy at Tufts University and spokesperson for the American Heart Association. "We still don't know whether there is benefit of omega-3 fatty acids as primary prevention [in a healthy population] or in a population that is less well treated. I don't think this study would necessarily cause a change in the current recommendations," she says.
Those guidelines advise most adults to consume two meals of fatty fish, such as salmon or mackerel, each week, amounting to an average of 400 mg to 500 mg of omega-3s in the diet per day. For people with heart disease, like those in the Dutch study, the recommendation is to double that amount.
So far, says Lichtenstein, experts are limiting their recommendations to omega-3s from dietary sources since studies have not shown that supplements, in the form of fish-oil capsules, can definitively lower the risk of heart attack or death from heart disease. More research is needed to answer that question and to determine what role omega-3 fatty acids may play in preventing heart disease in heart-disease-free people or in those who have had a previous heart attack but whose risk factors are not being controlled as well as those of the volunteers in the current study.