And Lake Superior fish are good sources of oil, according to Paul Addis, professor with the University of Minnesota Department of Food Science and Nutrition. Lake herring is also a good source of omega-3 oils. Addis discovered this through Sea Grant-funded research a decade ago. Before that, it was assumed that only saltwater fish were high in omega-3's. They prevent blood clots by reducing the activity of the blood platelets.
Platelets are the clotting factors in blood that are the number one trigger of heart attacks.
To achieve maximum benefits from fish oil, people would need to eat more than 1 pound per day of a fatty fish, such as tuna, salmon, or lake trout. Eating this much fish is unrealistic for some people. Fish oil capsules offer another source. Fish oil capsules are big business. The oil used in the capsules is routinely processed to remove some of the rancid compounds and contaminants like PCBs.