Fish oil is now the second most popular food supplement behind vitamin-mineral supplements. An estimated 10% of Americans ingest a daily fish oil supplement, with the most likely motivation being that it's thought to be an effective measure to protect against the onset of cardiovascular disease, the number one killer of Americans. Some people ingest fish oil because they've heard that it offers potent anti-inflammatory effects, and as such may reduce the effects of various inflammation-based diseases, such as arthritis and asthma. The key elements that provide these protective effects in fish oil are the omega-3 fatty acids, eicosapentaenoic acid, and docosahexaenoic acid, or simply, EPA and DHA. The omega-3 fatty acids are considered essential in human nutrition since they cannot be synthesized in the human body, but this statement needs to be qualified. What is actually listed as "essential" is not the active forms of omega-3, EPA and DHA, but rather alpha-linoleic acid (ALA). The reason for this is two-fold. For one, ALA is found in a greater variety of foods compared to EPA and DHA, which exist preformed in various types of fatty fish, such as mackerel, sardines, halibut, salmon, and others. As such, it's easy to obtain ALA from food, since many people simply don't like to eat fish. However, the problem with this is that ALA is a precursor to the more active EPA and DHA forms. It must be converted by desaturase enzymes into the EPA and DHA, and these enzymes are not that efficient for this conversion. As such, less than 2% of ingested ALA is converted into DHA, and about 5% is converted into EPA. Women are able to convert more of ALA into active omega-3 forms compared to men. This doesn't mean that ALA is useless since some studies show that it does provide some protective health benefits, including cardiovascular protection. But it isn't nearly as potent in this effect as the preformed versions, EPA and DHA that are found in fatty fish and fish oil. Bodybuilders often believe that using a supplement such as flaxseed oil, which contains 57% ALA, is suitable as a source of omega-3, but this is a mistaken notion due to the presence of ALA, rather than EPA and DHA in the oil.
The notion that EPA and DHA could provide cardiovascular disease (CVD) prevention came about in the 1970s, when two Danish scientists studied the diets of the native Intuit people living in Greenland, which relied on a few natural rich sources of EPA and DHA, such as fish and whale blubber. The scientists compared the rate of CVD in the Intuits to that of average Danish people, whose diets . . .