TUESDAY, June 13, 2006 (HealthDay News) -- Adding to an ongoing debate, a new study suggests that fish oil supplements do not reduce the incidence of serious abnormal heart rhythms or the risk of death linked to these arrhythmias.
The study was done in a high-risk group -- people who already had been given implanted defibrillators, devices that deliver shocks to keep a diseased heart beating. The European team conducted the trial because other studies of fish oil to prevent problems in such people have so far yielded inconclusive results.
Fish oil is rich in omega-3 fatty acids, which are known to have a beneficial effect on the heart. The American Heart Association recommends eating at least two fish meals a week as a protective measure.
But the new report in the June 14 issue of the Journal of the American Medical Association. found no such protective effect when it came to arrhythmias.
The finding does not affect the AHA recommendation, said Alice R. Lichtenstein, a professor of public health and family medicine at the Tufts University Friedman School of Nutrition and vice chairwoman of the heart association's nutrition committee.
"The study did answer for one aspect of the relationship between omega-3 fatty acids and abnormal heartbeats," Lichtenstein said. "But that doesn't mean that [levels of] fish and omega-3 fatty acids are not related to the risk of developing heart disease."
The 546 people in the study had clearly developed heart disease -- their defibrillators were implanted because they had either malignant ventricular tachycardia or ventricular fibrillation, two potentially fatal heart-rhythm abnormalities.
During their treatment at one of 26 European cardiology clinics, some of the patients were told to take two grams a day of fish oil, while others took a placebo.
According to the researchers, the death rate for the two groups was virtually similar: 33 percent of those taking the placebo and 30 percent of those taking the supplements died in the course of the study.
The findings "do not indicate evidence of a strong protective effect of intake of omega-3 fatty acids" for such patients, the researchers concluded.
The result came as a surprise to Dr. Roger Blumenthal, director of the Johns Hopkins Ciccarone Preventive Cardiology Center in Baltimore.
"We had data from some previous studies that showed a significant decrease in cardiac events," Blumenthal said. "We expected the study to show a benefit. But the whole purpose of these randomized trials is to verify reported effects."
Blumenthal said the report was "a disappointing one, but obviously an important one." The hope that omega-3 fatty acids would help people with weakened heart muscles has been dashed, he said.
For her part, Lichtenstein stressed that the European finding may well be true, "but there are other ways that [omega-3 fatty acids] are related to reducing the risk of heart disease that are not addressed in this particular study."
She noted that "the individuals in this study were not fit when the intervention was initiated," she said, so the nutrients' effect on healthier individuals remains unknown.
There is also evidence that omega-3 fatty acids have a beneficial cardiac effect themselves, she said. "Eating fish also replaces foods that have saturated fats in the diet," such as fatty meats, "so there is a double-dose effect," Lichtenstein said.
Eating fish, rather than taking a supplement, is always the best way to get the benefits of omega-3 fatty acids, she added. "At this point, for the general population, there are no good data to support the belief that fish oil supplements should be taken to prevent cardiovascular disease," Lichtenstein said.
For more on omega-3 fatty acids, head to the American Heart Association.