Fish oil has health benefits for many conditions, especially those involving the heart and cardiovascular system. Fish oil lowers blood pressure and triglyceride levels. Triglycerides are fats that have to do with cholesterol. Fish oil cuts the risk for heart disease and stroke.

Fish oil has a beneficial effect on mood, and is helpful for ADHD, Alzheimer's disease, depression and disorders of cognition.

Some of the fish that have high amounts of omega-3 fatty acids are cod, halibut, herring, and tuna, not to mention seal blubber and whale blubber.

"A lot of the benefit of fish oil seems to come from the omega-3 fatty acids that it contains. Interestingly, the body does not produce its own omega-3 fatty acids. Nor can the body make omega-3 fatty acids from omega-6 fatty acids, which are common in the Western diet. A lot of research has been done on EPA and DHA, two types of omega-3 acids that are often included in fish oil supplements."

http://www.webmd.com/vitamins-supplements/ingredientmono-993-FISH+OIL.aspx?activeIngredientId=993&activeIngredientName=FISH+OIL&source=2&ecd=wnl_hbn_062110