Giana Angelo, Ph.D.
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are very long-chain, highly unsaturated fatty acids derived from alpha-linolenic acid (ALA). ALA is an essential fatty acid and the parent compound from which all omega-3 polyunsaturated fatty acids (PUFAs) are made. Rich dietary sources of ALA are canola oil, flaxseeds, and walnuts. Though EPA and DHA are generated in the body from dietary ALA, they can also be obtained directly from food (especially oily fish) and supplements. The advantage of increasing EPA and DHA content in cells and tissues to improve health and prevent disease is an area of intense research. In particular, the C20-22 omega-3 fatty acids EPA and DHA, often referred to as “fish oils,” benefit cardiovascular health by modulating blood lipid levels, inflammation, and the function of endothelial cells (cells that line blood vessels) and cardiomyocytes (heart muscle cells).
A recent systematic review and meta-analysis, published in the Journal of the American Medical Association (JAMA), concluded that supplementation with omega-3 PUFAs is not associated with a statistically significant reduction in the risk of major cardiovascular events. A meta-analysis is a statistical method that combines the results from several randomized, clinical intervention trials (RCTs) that address similar questions. Combining multiple trials increases the probability of detecting smaller group differences if present. However, selection criteria for including or excluding studies can strongly influence the results of the meta-analysis and represent an important methodological limitation. In the present analysis, the authors pooled data on major cardiovascular events (all-cause mortality, cardiac death, sudden death, myocardial infarction, and stroke) from 20 RCTs of omega-3 PUFA administration with a combined total of 68,680 patients.
An emerging theme from the JAMA study, as well as several other reviews on this topic, is that omega-3 supplementation appears to be better at prevention (“primary prevention”) than therapy (“secondary prevention”) of cardiovascular diseases (CVD). Notably, the vast majority of the pooled RCTs were secondary prevention trials, meaning that the recruited subjects had pre-existing CVD or were at increased cardiovascular risk. Thus, supplementation with omega-3 PUFAs may not reduce the risk of cardiovascular events in patients with a history of CVD, particularly when used in combination with drug therapy, such as statins, aspirin, or anti-hypertensive medications. However, observational epidemiologic studies have consistently found that increased fish consumption or higher omega-3 PUFA blood levels are associated with a significantly lower risk of cardiovascular events in healthy adults.
Beyond cardiovascular health, EPA and DHA are important for visual and neurological development, exert anti-inflammatory effects, and may slow cognitive decline with aging (see essential fatty acids). If you do not regularly consume fish, LPI recommends a two-gram fish oil supplement several times per week (see Prescription for Health). Consumption of fish or fish oil may not be suitable for all individuals, such as vegetarians, vegans, or those with seafood allergies. Alternative sources of C20-22 omega-3 fatty acids, produced in yeast or algae, are commercially available.
Last updated November 2012