Omega-3 fatty acids and cardiovascular disease: A case for omega-3 index as a new risk factor

Abstract

The omega-3 fatty acids (FAs) found in fish and fish oils (eicosapentaenoic and docosahexaenoic acids, EPA and DHA) have been reported to have a variety of beneficial effects in cardiovascular diseases. Ecological and prospective cohort studies as well as randomized, controlled trials have supported the view that the effects of these FAs are clinically-relevant. They operate via several mechanisms, all beginning with the incorporation of EPA and DHA into cell membranes. From here, these omega-3 FA alter membrane physical characteristics and the activity of membrane-bound proteins, and once released by intracellular phospholipases, can interact with ion channels, be converted into a wide variety of bioactive eicosanoids, and serve as ligands for several nuclear transcription factors thereby altering gene expression. In as much as blood levels are a strong reflection of dietary intake, it is proposed that an omega-3 FA biomarker, the omega-3 index (erythrocyte EPA+DHA) be considered at least a marker, if not a risk factor, for coronary heart disease, especially sudden cardiac death. The omega-3 index fulfils many of the requirements for a risk factor including consistent epidemiological evidence, a plausible mechanism of action, a reproducible assay, independence from classical risk factors, modifiability, and most importantly, the demonstration that raising tissue levels will reduce risk for cardiac events. For these and a number of other reasons, the omega-3 index compares very favourably with other risk factors for sudden cardiac death.

RETRACTED ARTICLE: Omega-3 fatty acid levels in red blood cell membranes and physical decline over 3 years: longitudinal data from the MAPT study

“…This means that the plasma levels of PUFAs are more prone to reflect only the short-term fluctuations in the diet than the RBC membrane PUFA concentration (Harris et al 2013). Information on RBC membrane PUFA levels can therefore be considered as more accurate because it reflects PUFA intake over a period of several months, with less biological variability than plasma PUFAs (Harris 2007;Harris and Thomas 2010).…”

Reduced mania and depression in juvenile bipolar disorder associated with long-chain ω-3 polyunsaturated fatty acid supplementation

“…RBC EPA and DHA increased following supplementation (Figure 1). The o-3 index (RBC EPA þ DHA%, Harris, 2007) increased from 4.2 ± 2.1 to 7.8 ± 1.9.…”

n-3 fatty acids and cardiovascular disease

“…Recently, Harris 27 has presented evidence that EPA and DHA in red blood cells, expressed as weight percent of total fatty acids, the omega-3 index, might be regarded as a reflector of the omega-3 fatty acid content of myocardial cells. Furthermore, Shacky and Harris 27 have claimed that the omega-3 index may be considered a risk factor for sudden cardiac death, as an omega-3 index > 8% is associated with a 90% lower risk of sudden cardiac death, as compared to that in subjects with an omega-3 index < 4%.…”