It has been suggested that omega-3 fatty acids confer benefit in patients with known coronary heart disease by significantly reducing all-cause mortality and the risk of sudden death caused by cardiac arrhythmias. This may be as a result of the triglyceride-lowering effect of omega-3 fatty acids at high doses. Much of the evidence in favour of omega-3 in cardiovascular disease relates to studies which looked at the effects of increased intake from dietary sources. Oily fish (such as salmon and tuna), flaxseed, canola oil and walnuts, are all rich dietary sources of omega-3 fatty acids. Firm evidence for pharmacological supplementation exists in a few secondary prevention studies and recent National Institute for Health and Clinical Excellence guidance only recommends pharmacological omega-3 supplements to patients within three months of a myocardial infarction, to be continued for up to four years, assuming dietary intake is insufficient. There is currently little evidence for specific benefits of omega-3 supplementation in patients with diabetes.

Omega-3 and omega-6 fatty acids are called essential PUFAs as they cannot be synthesised 'de novo' in the body and must therefore be obtained from the diet.[1] The three major types of omega-3 fatty acids obtained from foods and used by the body, are ALA, EPA and DHA. The simpler omega-3 fatty acid ALA is converted to EPA and DHA, which are the two omega-3 fatty acids more readily used by the body and are important to maintain normal growth, development and brain function. ALA is therefore an essential nutrient.[1,2]

Omega-3 fatty acids from dietary sources may have beneficial effects in primary prevention of cardiovascular disease. In terms of secondary prevention of cardiovascular disease, omega-3 PUFA intake, either from dietary sources or as supplementary pharmacological preparations may have beneficial effects. However, some questions remain with regard to patient selection, timing of MI and duration of therapy. The current NICE guidance that recommends omega-3 therapy only in individuals having had MI less than three months prior to initiation probably limits the utility in other high-risk post-MI patients. This is an issue that needs to be addressed. Similarly, further studies are required to clarify the benefits of omega-3 PUFA beyond four years.
Further cardiovascular morbidity and mortality studies are required in patients with diabetes using pharmacological omega-3 PUFA therapy, especially in addition to what would be considered standard therapy for patients with diabetes. Similar studies in patients with diabetes who are unable to tolerate standard lipid lowering therapy would be useful to see if the apparent benefit of higher omega-3 PUFA in diabetic women would support the use of omega-3 PUFA as an alternative in these patients to try and reduce CV risk.[37] The role of omega-3 PUFA pharmacological supplementation in primary prevention of cardiovascular disease and the management of hypertriglyceridiaemia alone cannot currently be recommended, but dietary increases in omega-3 PUFA consumption should be encouraged.