What can we expect from omega-3 fatty acids?
ABSTRACTOmega-3 fatty acids are abundant in fish oil. A high dietary intake of omega-3 fatty acids has been strongly linked to lower rates of cardiovascular disease in epidemiologic studies. Fish oil supplements lower triglyceride levels and may have other benefits such as preventing arrhythmias, reducing inflammation (although they have minimal impact on C-reactive protein), inhibiting platelet aggregation, and lowering blood pressure, all of which should reduce cardiovascular risk.
KEY POINTS
- The American Heart Association recommends that healthy people consume fatty fish at least twice a week. The recommendation for people with coronary artery disease is 1 g of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) per day.
- A formulation of EPA 465 mg plus DHA 375 mg is available by prescription and is approved for treating triglyceridemia in excess of 500 mg/dL. The dose is 2 to 4 capsules per day.
- Experts generally believe that omega-3 fatty acids reduce arrhythmic events. Nevertheless, we lack clear evidence of their clinical effectiveness, and their use for such purposes is off-label.
- Overall, omega-3 fatty acids have minimal side effects.
No effect on restenosis
These agents, however, have no effect on restenosis rates after coronary angioplasty, as restenosis is mediated less by plaque formation than by intimal hyperplasia and negative remodeling within the endothelium. Even at high doses of 5 mg/day before angioplasty, omega-3 fatty acids failed to reduce the incidence of restenosis at 6 months.28
Modest effect on blood pressure
Omega-3 fatty acids are incorporated into the phospholipid bilayer of the endothelial membrane, increasing its fluidity and promoting vasodilation via an increase in nitric oxide production. These effects suggest they could be used to help control blood pressure, but studies have shown this effect to be minimal.
In a meta-analysis of 36 trials, Geleijnse et al29 estimated the reduction in blood pressure to be 2.1 mm Hg systolic and 1.6 mm Hg diastolic. The median intake of fish oil was 3.7 g/day. The largest reductions were in patients with known hypertension and those over age 45.
These findings seem consistent with the hypothesis that omega-3 fatty acids affect the endothelium, given that the arterial wall tends to become stiffer with age. Overall, however, the results of a number of studies show that fish oil supplementation is of limited clinical use in lowering blood pressure.
Confounding factors among studies
The variability in the results of different studies may be due to confounding factors such as the patients’ baseline diet, the doses of EPA and DHA given, the duration of treatment, and patient compliance. These factors must be considered when examining evidence supporting the use of omega-3 fatty acids.
