Omega-3 Fatty Acids—Science, Efficacy, and Clinical Use in Cardiology

Omega-3 Fatty Acids—Science, Efficacy, and Clinical Use in Cardiology

Butler William E
US Cardiovascular Disease 2007
Published: July 2007
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Studies have shown that omega-3 fatty acids (FAs) can promote cardiovascular health by both primary and secondary prevention of cardiac disease, and most notably by reducing fatal cardiovascular events including sudden cardiac death (SCD). For example, recent evidence from secondary prevention trials has suggested that intake of 850mg/day of omega-3 FAs can reduce the risk of coronary heart disease (CHD) events by 25% and SCD by about 45%.1 Furthermore, of the three known omega-3 FAs there is evidence that eicosapentanoic acid (EPA) is particularly biologically important. Given the strength of the evidence, blood levels of omega-3 FAs may have value as biomarkers to evaluate risk for cardiovascular events, leading to opportunities for earlier intervention in high-risk cases.

What Are Omega-3 Fatty Acids?
Omega-3 FAs, like omega-6 FAs, are a type of polyunsaturated FA (PUFA) that the body is unable to synthesize and that must, therefore, be obtained through the diet. The omega-3 FAs are distinguished from other classes of FAs by the structure of their carbon chains. FAs are chains of carbon atoms that are labeled with the ‘alpha’ carbon proximal to the carboxyl group and end with the distal ‘omega’ carbon. The omega-3 FAs contain a double bond between the third and fourth carbons from the omega carbon. All of the omega-6 FAs contain their first double bond between the sixth and seventh positions from the omega carbon. Humans lack the enzymes required to place a cis double bond at the omega-3 or omega-6 positions. Thus, omega-6 and omega-3 FA are essential FAs and must be supplied in our diet. Omega-6 FAs are present in grains and nuts. Omega-3 alphalinolenic acid (ALA) is an 18-carbon FA that is found in plants but cannot be easily elongated to the more important 20-carbon form by humans. The mega-3 FAs EPA and docosahexaenoic acid (DHA) are synthesized by phytoplankton and then consumed and concentrated by fish. They may be acquired in the diet by fish consumption, by foods fortified in omega-3, or by further concentration and specification in high-concentrate nutritional omega-3 supplements.

The 1982 Nobel Prize2 was awarded for the discovery of omega-6 FA in the form of prostaglandins and related biologically active substances that are metabolites of arachidonic acid (AA), the 20-chain omega-6 FA that is a foundation of the inflammatory response. These omega-6 AA metabolites include prostaglandins, such as the thromboxanes and leukotrienes. Subsequent to that award, it has become appreciated that the proinflammatory 20-chain omega-6 arachidonic pathway is counterbalanced by an anti-inflammatory pathway based on the 20-chain omega-3 EPA. The scientific literature is growing regarding the tremendous health benefits of omega-3 supplementation both for overall health and disease prevention and for the treatment of many inflammatory conditions.

Grains are rich in omega-3 FA. The agricultural revolution greatly increased the human food supply by permitting the large-scale production of grains. The caloric plethora afforded by the agricultural revolution, however, has resulted in disproportionate ratios of omega-6 to omega-3 FA in the modern diet: while the optimal ratio in the body of omega-6 to omega-3 is approximately 1:1, the current ratio in Westernized societies is approximately 16:1,3 with a resultant increase in inflammatory disorders.

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