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.