Fish oil is the childhood nightmare for many of our grandparents. And while fish oil supplements could be recommended for some cardiac patients, others could experience negative effects, as found by a meta analysis carried out at St. Michael's Hospital and University of Toronto and published in the Canadian Medical Association Journal.

The team analyzed data coming from researches made on subjects with implantable cardioverter defibrillators who used fish oil supplements, and discovered mixed results from one study to another, pointing fish oil could be beneficial to some while affecting negatively others.

"Fish oils can have complex and varied effects on the heart. These effects include blocking cardiac ion channels, reducing fibrosis in response to mechanical stress, decreasing blood coagulation, and possibly altering immune function," co-author Dr. David Jenkins, a UT Professor of Medicine and director of the Clinical Nutrition and Risk Factor Modification Center at St. Michael's Hospital, said.

Many large-scale population (epidemiologic) researches and randomized controlled trials showed that the consumed of DHA and EPA as dietary fish or fish oil supplements can lower the likelihood of death, heart attack and dangerous abnormal heart rhythms in cardiovascular disease patients, as omega3 essential fatty acids hamper the hardening of the arteries and decrease blood pressure. On the other side, high amounts of these acids boost the risk of bleeding.

Even if the results of various researches have a mixed result, recent data points that the effects of the fish oil can be biased by several factors, like stable angina or ventricular tachycardia, when patients do not take antiarrhythmic drugs.

"Fish oils have promise as beneficial in cardiovascular disease but our work highlights our gaps in understanding and the need for more research," Dr. Paul Dorian, a cardiologist at St. Michael's Hospital and U of T Professor of Medicine University of Toronto, commented.