Fish oil - or, more precisely, omega-3 fatty acids - offers so many health benefits, including reduction of risk of heart disease, that most experts recommend that everyone eat more coldwater, oily fish, (such as salmon, sardines, herring, and black cod). Fish provide both of the omega-3s: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) our bodies need. Another omega-3 precursor, alpha-linolenic acid (ALA), occurs in nuts (especially walnuts), leafy vegetables, flaxseed and some animal fat, especially from grass-fed animals. The body must convert ALA into EPA and DHA, an inefficient process.
Omega-3s are so important to heart health that my longstanding recommendation has been to consume two to three servings of fish per week or to take a fish oil supplement if you don't like fish. The American Heart Association recommends eating at least two fish meals a week. I eat fish often and also take 2-3 grams of supplemental fish oil a day.
We know that populations that eat fish regularly live longer and have less chronic disease than populations that do not. This may be partly because fish displaces meat in their diets. Certainly, fish provides high-quality protein without the saturated fat present in meat and poultry. In addition, the benefits of supplemental fish oil for people with heart disease are well established: reduction of serum triglycerides by 25 to 30 percent, slowing of the buildup of atherosclerotic plaques that can clog coronary arteries, slight lowering of blood pressure, decreased clotting tendency of the blood, and reduced risk of death, heart attack, dangerous abnormal heart rhythms, and strokes. Fish oil also may benefit people who have diabetes, PMS, breast cancer, memory loss, depression, insulin resistance, rheumatoid arthritis, and other inflammatory conditions.
One widely cited study did find that fish oil tends to raise ("bad") LDL cholesterol by five to 10 percent while raising ("good") HDL by one to three percent. But that's not the whole story, which is rather complicated. I discussed your question with integrative cardiologist Stephen DeVries, M.D. of Northwestern University's Center for Integrative Medicine and Division of Cardiology in Chicago. He explained that the risk of heart attacks is more dependent on the number of LDL particles than on the amount of cholesterol they contain. Fish oil can slightly increase the amount of cholesterol in LDL, but it also significantly lowers the number of LDL particles. The end result is beneficial. There's no reason to worry that taking fish oil will sabotage your cholesterol control and every reason to believe that it will benefit your heart and general health.
Andrew Weil, M.D.