Biological mechanisms and cardiovascular effects of omega-3 fatty acids.

The mechanisms and cardiovascular effects of omega-3 fatty acids are reviewed. Omega-3 polyunsaturated fatty acids are the major ingredient found in commercially available fish oil products. The incidence of many diseases, including coronary heart disease, diabetes mellitus, and psoriasis, is lower in Eskimos, who ingest diets rich in omega-3 fatty acids, compared with European controls. Potential mechanisms by which these fatty acids cause their many physiologic effects include competing with omega-6 fatty acids for prostaglandin and leukotriene pathways and enhancing cell membrane fluidity by virtue of the high degree of unsaturation. Numerous studies have documented longer bleeding times and decreased platelet aggregation in subjects ingesting omega-3 fatty acids. Omega-3 fatty acids may reduce serum cholesterol concentrations by decreasing the synthesis of very low density lipoprotein and, therefore, low-density lipoprotein. Blood viscosity is significantly and uniformly lower in subjects receiving omega-3 fatty acids compared with controls. Potential risks of supplementation with fish oils include hypervitaminosis A and D, vitamin E deficiency, increased bleeding times, decreased platelets, and ingestion of contaminated fish. Supplementation with moderate amounts of omega-3 fatty acids appears to be relatively safe. Possible adverse effects include nausea, diarrhea, and a "fishy" taste. Properly controlled, long-term clinical trials are needed to determine whether supplementation with omega-3 fatty acids would be therapeutically beneficial in various patient populations and disease states.