In addition, prostaglandins can stimulate tumor cell growth. Fish oil can inhibit the enzyme responsible for prostaglandin synthesis called prostaglandin synthase. After a high intake of fish oil, prostaglandin (especially in the tumor cells) is decreased significantly, which in turn, slows tumor growth.

Notably, when we say “fish oil,” of course we should generally keep in mind the following cold-water fish:  mackerel, salmon, sardines.  Other species may likewise be of value.

Fatty fish and fish oil are reliable sources of EPA and DHA, the most health promoting of the essential fatty acids. While several vegetable sources, such as flaxseeds, soybean oil and walnuts, contain omega-3, that fat comes in the form of alpha-linolenic acid (ALA), which is chemically a precursor to EPA and DHA. The body must convert the ALA into the more usable EPA and DHA, a process that brings only a limited health benefit and is compromised by the consumption of more harmful fatty substances such as saturated fats and trans fats. The longer one lives, the less efficient one’s body gets at converting ALA into EPA and DHA.

Researchers discovered the essential fatty acids and their beneficial properties while studying the Inuit people of Greenland. It is well known that Inuit people eat an extremely high-fat diet, yet they rarely suffer from maladies associated with the American diet such as heart disease and rheumatoid arthritis. The solutions to this riddle are EPA and DHA [source: Larsen]. According to the American Heart Association, fish oil helps maintain cardiovascular health by these mechanisms:

* Reducing and reversing inflammation
* Reducing the coagulation of blood platelets (clotting)
* Lowering triglyceride levels
* Slowing down artherosclerosis (thickening of artery walls)
* Lowering blood pressure
* Steadying the heart rhythm

Anti-inflammatory qualities are central to why fish oil is so highly regarded for circulatory health. Chronic inflammation is the unsung cause of health conditions ranging from heart attack and stroke to autoimmune diseases such as lupus. Non-steroidal anti-inflammatory drugs (NSAID) are among the most popular pharmaceuticals on the market, but they can have severe side effects. The omega-3 fats can match these drugs in effectiveness but are much safer and cheaper [source: Maroon and Bost], see: Fish Oil: The Natural Anti-inflammatory.