Studies conducted on Greenland Eskimos, which consume large amount of fish or marine mammals rich in omega-3 fatty acids and have a low incidence of cardiovascular disease or CVD, have suggested a protective effects of such fatty acids against these disease. Results of other epidemiological studies, randomized trials and animal investigations, have also suggested that omega-3 fats, and in particular long-chain omega-3 fatty acids, eicosapentaenoic aci or EPA and docosahexaenoic acid or DHA have cardiovascular effects. These studies indicate that they have anti-inflammatory, antiatherogenic, and antiarrhythmic effects, which are considered plausible mechanisms for reducing the risk of cardiovascular disease.
Omega-3 fatty acid supplements and secondary prevention of CVD
In a study published on Archives of Internal Medicine a research team, using a meta-analysis of randomized, double-blind, placebo-controlled trials, has evaluated the preventive effect of omega-3 fatty acid supplements (omega-3 fatty acid supplements for at least 1 year, with a daily dose of EPA or DHA ranged from 0.4 to 4.8 g/d, and a follow-up period ranged from 1.0 to 4.7 years) in the secondary prevention of cardiovascular disease, i.e. among patients with a history of cardiovascular disease (not in healthy individuals).
The study involved 20485 patients, male or female aged ≥18 years, 10259 randomized to a placebo group and 10226 randomized to an intervention group. Placebo groups received vegetable oils (sunflower oil, olive oil, and corn oil), mixed fatty oil, and other “inert” or ill-defined substances (aluminum hydroxide and unspecified placebo).
The meta-analysis showed insufficient evidence of a secondary preventive effect of omega-3 fatty acid supplements against overall cardiovascular events, which include peripheral vascular disease, angina and unstable angina, transient ischemic attack and stroke, fatal and nonfatal myocardial infarction, sudden cardiac death, cardiovascular death, congestive heart failure, and nonscheduled cardiovascular interventions (i.e., coronary artery bypass surgery or angioplasty).
Moreover, no significant preventive effect was observed in subgroup analyses by the following: history of cardiovascular disease, concomitant medication use (lipid lowering agents, no lipid-lowering agents, or antiplatelet agents only), country location (Western Europe, Northern Europe, United States, or Asia), inland or coastal geographic area, methodological quality of the trial, duration of treatment, type of placebo material in the trial (oil vs nonoil), dosage of EPA or DHA, or use of fish oil supplementation only as treatment.
The study showed insufficient evidence of a secondary preventive effect of omega-3 fatty acid supplements against overall cardiovascular events among patients with a history of cardiovascular disease.
Kwak S.M., Myung S-K., Lee Y.J., Seo H.G., for the Korean Meta-analysis Study Group. Efficacy of omega-3 fatty acid supplements (eicosapentaenoic acid and docosahexaenoic acid) in the secondary prevention of cardiovascular disease. A meta-analysis of randomized, double-blind, placebo-controlled trials. Arch Intern Med 2012;172(9):686-694. doi:10.1001/archinternmed.2012.262