Another scientific review has concluded that omega-3 fatty acids are beneficial to heart health, and proposes a new measure of cardiovascular risk called the “omega-3 index”.
The measure, merely a quantification of the fatty acid status of a person, could help physicians and heart patients achieve levels of omega-3 that are reported scientifically to provide cardiovascular benefits.
“As is the case now for LDL [cholesterol], in the future cardiac societies might very well recommend [measurement of] EPA and DHA to become goal orientated,” wrote Clemens von Schacky from Ludwig-Maximilians-Universitat in Munich, and William Harris from the University of South Dakota.
Higher omega-3 fatty acids have been linked to a wide-range of health benefits, including reduced cardiovascular disease (CVD), healthy baby development during pregnancy, joint health, behavior and mood, and certain cancers.
Their new review, published in the journal Cardiovascular Research, reviewed epidemiological and four large scale intervention studies, and concluded that the majority of the evidence supports the benefits of omega-3 intake for heart health.
The mechanism behind such benefits, said von Schacky and Harris, is proposed to be the incorporation of EPA and DHA into cell membranes, which replace other fatty acids and changes the properties of the cell. Such changes include expanding blood vessels to improve blood flow, reducing inflammation, and lowering blood triglyceride levels.
And since the omega-3 are incorporated into the cell it would be worthwhile measuring the omega-3 cellular content as a marker of cardiovascular risk, said von Schacky and Harris. “The possibility that an omega-3 biomarker might have clinical prognostic utility, must be considered,” they said.
Von Schacky and Harris proposed, therefore, the “omega-3 index”, defined as the percentage of EPA plus DHA in red blood cell membranes, relative to all other fatty acids.
Using data from the scientific literature, the reviewers calculated that an omega-3 index value of eight per cent or above is associated with a 90 per cent reduction in the risk of sudden cardiac death, compared to a value of four per cent or less.
“The standard dose is one gram per day of omega-3 fatty acids- eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) - recommended by cardiac societies. In standard omega-3 fish oil, 300 mg EPA and DHA is found in each 1000 mg of fish oil. It is probably far from ideal for everybody, since not only this standard dose, but also diet, individual genetic background, BMI… and other factors all taken together probably determine the omega-3 fatty acid status of a given person,” wrote the reviewers. Thus measuring the cellular level of omega-3 fatty acids is projected to be a better marker than measuring intake from a variety of sources.
The risk of pollutants from oily fish, such a methyl mercury, dioxins, and polychlorinated biphenols (PCBs) have led some to advocate a reduction in fresh fish intake, despite others advising that the benefits of fish consumption outweigh the risks.
Such conflicting views on fish intake have seen the number of omega-3 enriched or fortified products on the market increase as consumers seek omega-3s from ‘safer' sources. Most extracted fish oil are purified to remove contaminants. Indeed, von Schacky and Harris recommend that such contaminants be avoided. There are a number of good fish oils on the market, but one of the best new ways to get omega-3 polyunsaturated fats is from krill oil.
Cardiovascular Research (doi: 10.1016/j.cardiores.2006.08.019)