Is there something fishy going on with omega-3 fatty acids?
For years, major health and medical organisations have recommended fish oil supplements rich in omega-3s to reduce the threat of heart disease. In Europe, where support is particularly enthusiastic, a doctor's failure to recommend the supplements is viewed by some as bordering on malpractice.
But several recent studies have raised questions about the benefits of fish oil, sparking no small amount of confusion. A report published yesterday in the Journal of the American Medical Association clouded the picture further by concluding omega-3 polyunsaturated fatty acids did not lower the risk of heart attack, stroke or premature death.
The study, by medical researchers at the University of Ioannina in Greece, did not involve a new clinical trial of the supplement. Instead, it re-examined the results of 20 previous studies dating to 1989 that included nearly 70,000 people.
Study authors said early trials of omega-3 supplements and cardiovascular health "showed strong, significant effect". However, as more randomised studies were performed, "the effect became weaker and non-significant".
One reason for this, according to the authors, is an early and influential trial was conducted as an open-label study, in which patients and researchers knew when they were taking the supplement. That study involved mostly men who had suffered heart attacks, said Dr Moses Elisaf of the University Hospital of Ioannina, a senior author of the study. "This evidence," he said, "should not be generalised to any type of patients or apparently healthy individuals."
There was no "statistically significant" association with all-cause mortality, cardiac death, sudden death, heart attack, and stroke when all supplement studies were considered.
Dr Evangelos Rizos, chief author of the study, said: "Our findings do not justify the use of omega-3 as a structured intervention in everyday clinical practice or guidelines supporting dietary omega-3."
Dr Robert Bonow, a Chicago cardiologist who was not involved in the study, said he tended to agree with the authors' conclusion that not everyone would be helped by taking omega-3 supplements.
Bonow, a former president of the American Heart Association, said there was no evidence that omega-3 prevented heart attacks. For most people, any potential benefits of supplementation probably paled in comparison with exercising, maintaining a proper weight and addressing high cholesterol and high blood pressure, he said.
However, Bonow said it appeared the supplement was helpful to people with very weak hearts.
Additional reporting by Agence France-Presse