Omega-3 fatty acids from fish lower risk of exercise-induced Heart attack

Finland: Long-chain omega-3 polyunsaturated fatty acids (PUFA) from fish are known to provide protection from coronary heart disease (CHD). However, methylmercury present in fishes is associated with a higher risk of CHD and may diminish the cardioprotective effect of long-chain omega-3 PUFA.

A recent study published in the BMJ journal Heart has found that a higher circulating concentration of the omega-3 fatty acids lowered the risk of exercise-induced myocardial ischemia, only in men with a CHD risk. And, a higher concentration of hair mercury was associated with a higher occurrence of exercise-induced myocardial ischemia.

Omega-3 fatty acids are a class of essential polyunsaturated fatty acids with the double bond in the third carbon position from the methyl terminal (hence the use of "3" in their description). Foods high in omega-3 fatty acids include salmon, halibut, sardines, albacore, trout, herring, walnut, flaxseed oil, and canola oil. Other foods that contain omega-3 fatty acids include shrimp, clams, light chunk tuna, catfish, cod, and spinach.

Myocardial ischemia, also called cardiac ischemia occurs due to reduced blood flow to the heart, resulting in insufficient oxygen supply to the heart muscle. The reduced blood flow is usually the result of a partial or complete blockage of your heart's arteries (coronary arteries). It reduces the ability of the heart muscle to pump blood. It can lead to a heart attack or can cause abnormal heart rhythm.

Behnam Tajik, Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland, and colleagues investigated the associations of serum long-chain omega-3 PUFA and hair mercury with the odds for myocardial ischemia during exercise.

The study involved analysis of 2199 men aged 42–60 years from the Kuopio Ischaemic Heart Disease Risk Factor Study from 1984–89. The men performed a maximal symptom-limited exercise stress test using an electrically braked bicycle ergometer. ORs for exercise-induced myocardial ischemia were estimated with logistic regression.

• Of the 2199 men, 342 had a history of CHD.


• In the multivariable analysis, those in the highest versus lowest serum long-chain omega-3 PUFA quartile had 33% lower odds of myocardial ischemia. The association was stronger among those with CHD history, than among those without.


• Higher hair mercury concentration was associated with increased odds for myocardial ischemia in the entire population.

Based on the study, the authors concluded that higher circulating concentrations of the long-chain omega-3 PUFAs, a marker for fish consumption, were associated with a lower occurrence of exercise-induced myocardial ischemia, but only among men with CHD history. Hair mercury concentration was directly associated with the occurrence of exercise-induced myocardial ischemia in the entire study population.