Cardiovascular Disease, Omega 3 and the Study with the Wrong Conclusions
Heart diseases: omega-3 expert clarifies all doubts
Prof. William S. Harris, a world authority on the role of omega-3 in cardiovascular diseases, criticizes the scientific basis that invalidates the conclusions of a recent meta-analysis that raised doubts about the benefits of these fatty acids. The recent doubts about the usefulness of taking Omega-3 to reduce the risk of cardiovascular diseases do not find support in the reality of facts and studies. This is stated by Prof. William S. Harris, professor of medicine at the University of South Dakota (Sioux Falls, USA) and Omega-3 expert, in response to the results published by Evangelos Rizos and colleagues in the Journal of the American Medical Association1 (JAMA). According to Harris, Rizos and colleagues reached too definitive conclusions based on a statistical analysis much more restrictive than those normally conducted and accepted by the scientific community.
Omega-3 and cardiovascular diseases, the reason for doubts
The first studies on the benefits of Omega-3 for the cardiovascular system date back to the 1970s. Since then, researchers have gathered more and more evidence supporting the hypothesis that increasing the intake of these fatty acids protects against diseases affecting the heart and blood vessels. Rizos and colleagues reviewed the results of 20 studies involving about 70,000 individuals to understand whether the intake of Omega-3 contained in fish oil really reduces the risk of heart attacks, strokes, or premature death due to cardiovascular problems. The purpose of the analysis, not the first of its kind, was to clarify a very current issue. However, the authors' conclusions created greater confusion on the topic. According to Harris, this confusion arises from the too sharp and generalized statements by Rizos and colleagues, based on a statistical analysis much more restrictive than the standards of the scientific community.
The importance of correct statistical analysis
The authors of the JAMA analysis concluded that Omega-3s have no statistically significant benefit on the risk of cardiovascular diseases. But what exactly does “statistically significant” mean in their interpretation? Statistical significance does not represent certainty, but probability. A statistically significant result is one that is much more likely to be true than false. When researchers perform statistical analysis, they choose how large the probability of error in the result can be. Rizos and colleagues decided to set their analysis parameters reducing this probability much more than scientists normally do. This arbitrary choice made the association between fish oil and cardiovascular risk reduction statistically non-significant. Harris explained that maintaining standard statistical parameters would instead have shown that fish oil reduces the risk of death by 9% due to heart disease. Of the 16 analyses of this type published by JAMA in 2012, Rizos’ is the only one to have changed the statistical parameters. This entirely subjective choice transformed a favorable effect of omega-3s into a non-effect.
Too low omega-3 amounts?
Harris also focused on another technical aspect of the studies involved in this analysis, noting that in 84% of cases Omega-3s were taken as ethyl esters. According to recent research, this particular form of omega-3 is poorly absorbed when taken on an empty stomach (24). This means that, in reality, most of the 70,000 individuals in the analysis may have taken omega-3 doses too low to benefit.
Is it right to generalize the results?
If those concerning statistics and dosages are quite technical details, the interpretation of results is much less so, and according to Harris the conclusions by Rizos and colleagues are too firm. The expert emphasizes that, based on current knowledge about Omega-3 benefits, it would have been more correct to make distinctions based on the clinical profile of patients taking these fatty acids. Harris agrees, for example, that in patients with an average age of 63 diagnosed with cardiovascular disease and following optimal medical therapy, taking about 1 gram daily of Omega-3 for 2 years does not reduce cardiovascular risks more than the ongoing medical treatments. The situation could be different for those taking higher doses of Omega-3 or taking 1 gram for more than 2 years. Moreover, Rizos’ analysis does not prove that Omega-3s give no benefit to patients at earlier disease stages or those not receiving optimal care. For these reasons, according to Harris, the results of this large analysis cannot be applied to reality.
Source:
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