By Dr. Bruce Holub, University of Guelph, Department of Biology and Nutritional Sciences, Canada. Conference paper presented at the American Oil Chemists Society (AOCS) Annual Meeting & Expo, May 2004. Theme: Cost-Effective Methods to Address the Leading Causes of Death & Chronic Diseases
Several studies have indicated an inverse relationship between the consumption of fish containing the omega-3 fatty acids as eicosapentaenoic acid (EPA, 20:5n-3) plus docosahexaenoic acid (DHA, 22:6n-3) and the risk of cardiovascular disease (CVD) and related events. Numerous intervention trials have indicated that fish oil supplements/concentrates enriched in EPA/DHA can favorably influence several risk factors for cardiovascular disease including reductions in fasting triglyceride levels, lowering of the triglyceride: HDL-cholesterol ratio, reduce blood viscosity, reduction in blood platelet reactivity and other thrombogenic risk factors, plus effects on other nonconventional risk factors which are not routinely measured in the public health care system. The latter include a favorable influence of omega-3 fatty acid intakes (as EPA/DHA) on postprandial lipemia, heart rate variability, arterial compliance as well as anti-arrhythmic affects. Data from the MRFIT study have indicated that increasing intakes of EPA/DHA (combined) up to approximately 650-700 mg/day are associated with overall reductions in all-cause as well as coronary disease-related mortality. The latter intake corresponds to approximately three fatty fish dishes per week and is in the range (650mg/day of EPA/DHA combined) as recommended daily intakes (workshop held at NIH, 1999) for healthy individuals. Considering that our group has estimated the average per capita intake of omega-3 fatty acid (as EPA/DHA) to be approximately 130 mg/day in Canada, current intakes are approximately one-fifth of those targeted as desirable for the general population for overall heart health.
The GISSI-Prevenzione Study has reported that, over and above the clinical use of appropriate pharmaceutical therapeutics plus a Mediterranean-type diet including some fish, supplementation with 900 mg/day of EPA/DHA (omega-3) could reduce sudden cardiac death by approximately 45% in patients having experienced a prior myocardial infarction (whereas vitamin E supplementation was without effect). The complementary potential of supplementation with EPA/DHA in patients taking statins is also of clinical interest. Recent evidence also suggests a plaque-stabilizing influence of fish-derived omega-3 fatty acid.
Alpha-linolenic acid (LNA), an omega-3 fatty acid of plant origin and a component of the Mediterranean-type diet, has exhibited an inverse relation with CVD-related ‘hard’ end-points in some, but not all, epidemiological studies. LNA is particularly enriched in flaxseed, canola oil and walnuts. The very limited conversion of LNA to EPA/DHA via metabolism is considered to mediate its cardioprotective effects.
The American Heart Association Guidelines for healthcare professionals have included the following recommendations with respect to omega-3 fatty acid supplements. ‘Consumption of one fatty acid meal per day (or alternatively, a fish oil supplement) could result in an omega-3 fatty acid intake (i.e. EPA and DHA) of ~900mg.day, an amount shown to beneficially affect coronary heart disease mortality rates in patients with coronary disease’. The current ‘nutrition gap’ for EPA/DHA (omega-3) intakes in North America and elsewhere can be alleviated by increased fish consumption, encapsulated supplements, or selected functional foods. Blood monitoring for omega-3 status is also gaining recognition in cardiovascular-related risk assessment.
“Omega-3 therapeutics” can be expected to offer both alternatives as well as complimentary options for preventive and management strategies via the informed practitioner.
