EPA supplements contain eicosapentaenoic acid (EPA), which is one of three essential omega-3 fatty acids. These are considered essential because the body cannot manufacture them and must get them from food or supplements. The only food sources of EPA are fatty fish such as salmon, mackerel, albacore tuna, herring, and sardines. Although the best way to consume enough EPA to obtain health benefits is to eat fish at least twice a week, EPA supplements have been shown to deliver similar benefits.
Two other omega-3 fatty acids are docosahexaenoic acid (DHA) and alpha-linolenic acid (ALA). EPA and DHA are found in fish, while ALA is found only in plant sources. Most EPA supplements also contain DHA, which together are considered the two substances responsible for the beneficial health effects of fish consumption.
For vegetarians who object to eating fish or taking fish oil supplements, it can be difficult to get enough EPA and DHA. The body is able to convert ALA from plant sources into EPA and DHA, but the process is inefficient and may not yield as much as eating fish or taking fish oil supplements. ALA is found in canola oil, flaxseeds, flaxseed oil, soybeans, soybean oil, and walnuts. Unfortunately research has not shown the same health improvements from consumption of ALA.
Results of research on the health benefits of fish oil have been pronounced enough that the American Heart Association has recommended that healthy people eat fish twice a week. The World Health Organization recommends 0.3 to 0.5 grams of EPA and DHA combined daily. In the United States, the average person only consumes about 0.1 to 0.2 grams of combined EPA and DHA each day.
Consumption of DHA and EPA supplements have been proven in research studies to reduce high blood pressure, reduce high triglycerides, lower the rate of death from heart disease, and reduce the symptoms of rheumatoid arthritis. Some studies have shown that DHA and EPA supplements and consumption of fish may reduce angina and help heart transplant and kidney transplant patients.
Preliminary studies also suggest that fish oil may improve learning and concentration in children, reduce symptoms of attention deficit hyperactivity disorder, and reduce symptoms of depression. EPA and DHA may also improve symptoms of psoriasis by reducing the inflammatory response in the body. More research will be needed to verify these results.
EPA and DHA supplements have few side effects. The most common are a fishy aftertaste, nausea, and “fish burps.” Fish oil may increase risk of bleeding, so patients with heart disease or those on blood thinners should consult a doctor before starting EPA supplements. Many species of fish contain high levels of mercury, so exceeding two servings per week can also have a negative health effect.