Cardiovascular Benefits
Coronary Artery Disease.
What's an Inuit? There has been a strong association between omega-3 fatty acids and cardiovascular health in many observational studies. Some of the initial evidence focused on the Inuit, an Eskimo population in Greenland, who have a significantly lower mortality rate from coronary artery disease despite high total fat intake and similar cholesterol levels when compared to the population of Denmark. The Inuit diet consists largely of marine mammals and fish, high in omega-3 fatty acids.
Kromann N, Green A. Epidemiologic studies in the Upernavik district, Greenland: incidence of some chronic diseases 1950-1974. Acta Med Scand. 1980;208:401-406.
Bang HO, Dyerberg J, Horne N. The composition of food consumed by Greenland Eskimos. Acta Med Scand. 1976;200:69-73.
Clinical Intervention Studies. Since the association was made in observational studies, researchers have conducted several interventional clinical trials that have shown decreased mortality from cardiovascular disease, specifically myocardial infarction in the past two decades.
One of the most well known studies, the GISSI-3 {Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardio (GISSI)-Prevenzione}, in which 11,324 people were given 1gram of omega-3 fatty acids or control for 24 months. This large study showed that persons given omega-3 fatty acid supplements had a 45% decrease in risk of sudden cardiac death and a 20% reduction in all-cause mortality.
GISSI-Prevenzione Investigators. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Lancet 1999;354:447-55.
Meta-Analysis. A meta-analysis recently published in the American Journal of Medicine reviewed 11 clinical intervention studies published between 1966 and 1999. The relative risk ratio for patients supplemented with omega-3 fatty acids as compared to controls was 0.7 (P<0.001), 0.8 for nonfatal myocardial infarctions (P=0.16) and 0.7 (P<0.001) for overall death.
What does this mean for you? Well, a meta-analysis groups the results of several studies to make more meaningful conclusions. If you eat a significant amount of fish or take an omega-3 fatty acid supplement, you can decrease your risk of dying by 30% or your risk of having a fatal heart attack by 20%. That is a pretty persuasive argument!
How does omega-3 lower cardiovascular risk? There has been a lot of research on this topic and there are several possible mechanisms for these beneficial effects:
- Lowering triglycerides (lipids in your bloodstream)
- Reducing endothelial dysfunction (making your blood vessels healthier)
- Inhibiting monocyte adhesion and inflammatory mediators (reducing inflammation)
- Reducing heart arrhythmias
- Reducing hypercoagulability (reducing the chance of blood clots)
The FDA approved a qualified health claim on the heart benefits of the omega-3 fatty acids. http://vm.cfsan.fda.gov/~dms/ds-ltr11.html
Hypertension
A meta-analysis on this issue, that included 17 clinical trials, concluded that supplementation with omega-3 fatty acids reduced both systolic and diastolic blood pressure in hypertensive patients. The effect on non-hypertensive patients was minimal.
Appel LJ. Miller ER 3rd. Seidler AJ. Whelton PK. Does supplementation of diet with 'fish oil' reduce blood pressure? A meta-analysis of controlled clinical trials.[comment]. [Journal Article. Meta-Analysis] Archives of Internal Medicine. 153(12):1429-38, 1993 Jun 28.
Arrhythmias
Several clinical intervention studies, including GISSI-3 mentioned above, have shown that omega-3 fatty acids reduce sudden death, especially in patients who have prior coronary artery disease. The decrease in sudden death is partly attributed to the reduction in fatal cardiac arrythmias. Recent animal studies are close to elucidating the mechanism behind this benefit.
De Caterina R. Madonna R. [Antiarrhythmia effects of omega-3 fatty acids. A review]. [Review] [86 refs] [Italian] [Journal Article. Review. Review, Tutorial] Italian Heart Journal: Official Journal of the Italian Federation of Cardiology. 3(3 Suppl):297-308, 2002 Mar.