Fish oil may be extracted directly or concentrated and put in capsule form. Active ingredients are ω-3 fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]). Western diets typically are low in ω-3 fatty acids.
Fish oil is used for prevention and treatment of atherosclerotic cardiovascular disease. Strong scientific evidence suggests that EPA/DHA 800 to 1500 mg/day reduces risk of MI and death due to arrhythmia in patients who have preexisting coronary artery disease and are taking conventional drugs. (See also the Agency for Healthcare Research and Quality EPC Evidence Report Effects of Omega-3 Fatty Acids on Cardiovascular Risk Factors and Intermediate Markers of Cardiovascular Disease.) It also reduces triglycerides in a dose-dependent way (25 to 40% with EPA/DHA 4 g/day) and slightly lowers BP (2 to 4 mm Hg with EPA/DHA > 3 g/day). Mechanisms are probably multiple but unknown. Benefits are suspected but not yet proved for primary prevention of atherosclerotic cardiovascular disease, treatment of RA (see also the Agency for Healthcare Research and Quality EPC Evidence Report Effects of Omega-3 Fatty Acids on Lipids and Glycemic Control in Type II Diabetes and the Metabolic Syndrome and on Inflammatory Bowel Disease, Rheumatoid Arthritis, Renal Disease, Systemic Lupus Erythematosus, and Osteoporosis), and prevention of cyclosporine nephrotoxicity.
Fishy eructation, nausea, and diarrhea may occur. Risk of bleeding increases with EPA/DHA > 3 g/day. Concerns about mercury contamination are not substantiated in laboratory testing. Even so, pregnant or breastfeeding women should not take ω-3 fatty acid supplements extracted from fish and should limit consumption of certain types and amounts of fish because of the potential risk of mercury contamination.
Last full review/revision May 2009 by Ara DerMarderosian, PhD
Content last modified August 2013