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EPA (eicosapentaenoic acid), along with docosahexaenoic acid (DHA), is an omega-3 essential fatty acid found in nuts, seeds, whole grains, dark leafy greens, and, most abundantly, in the natural oils of cold-water fish. Essential fatty acids (EFAs) are polyunsaturated fats that the body cannot produce and must be obtained from foods or supplements. Compared with vitamins and minerals, they are needed in relatively large amounts for the body to stay healthy. This is why EPA, DHA and the omega-6 polyunsaturated fats in common cooking oils are sometimes collectively termed "Vitamin F."

Why is it essential? Cells in every part of the body need essential fatty acids to maintain their thin, fatty, outer membrane, which is needed to transport nutrients in and out of the cell, produce energy, and manufacture hormones. The brain in particular has a high concentration of essential fatty acids and other fats necessary for proper nerve function and cognitive development. Cells that are weakened by a dietary shortage of essential fatty acids are unable to process serotonin and other neurotransmitters—a deficiency that can adversely effect mood and behavior. The eyes are also vitally in need of the proper EFA balance for optimal visual function. The body needs certain essential fatty acids to produce prostaglandins, hormone-like substances that have a wide range of effects in the body, including susceptibility to inflammatory conditions such as allergies, asthma, and rheumatic diseases. From the heart and gastrointestinal tract to the sex glands, stomach, and skin, every major organ system depends on essential fatty acids to perform its functions.

Daily requirement: There is no official RDA for EPA.

Deficiency risk factors: So-called primitive diets have much higher levels of EPA and the omega-3 essential fatty acids than do modern diets. Many modern diets have become unbalanced in their ratio of omega-3 to omega-6 essential fatty acids. (Vegetable cooking oils provide an overabundance of omega-6 EFAs.) Signs of a relative deficiency of the omega-3s may include weakness, fatigue, problems with vision, and tingling in arms or legs.

Optimal intake: Therapeutic doses of fish oil such as those used in most studies are relatively large, such as 3 grams or more of EPA plus DHA. For normal, healthy persons, however, an average daily dose is 300 to 600 mg of supplemental EPA.

Food sources: EPA is found in mackerel, salmon, herring, sardines, anchovies, albacore tuna, and wild game. Cod liver oil contains large amounts of EPA. Meat and eggs have some. In addition, the alpha linolenic acid found in flaxseed, hemp seed, and soybean oil is a precursor for EPA. Most nutritionally oriented doctors believe people do not eat enough omega-3 oil.

Safety: In general, essential fatty acid supplements are safe and nontoxic. Some people who supplement several grams of fish oil will experience gastrointestinal upset and burp up a "fishy" smell. Most people will not experience any side effects from taking average doses, like those recommended here. If you have a medical condition, however, that causes you to bleed excessively, you should talk to your doctor before taking essential fatty acids. Also, if you’re taking anticoagulant drugs like warfarin (Coumadin) for a heart condition, the blood-thinning effects of EFAs could theoretically present a hazard, although problems associated with increased bleeding time or blood loss have not been demonstrated in any clinical trials of EFAs. For the same reason, combining EFAs with aspirin should be approached with caution. Check with a nutritionally oriented doctor before taking more than 3 or 4 grams of fish oil for several months. Because cod liver oil has very high levels of vitamins A and D, this source of EPA needs to be approached with caution.

 
References

• Abdi-Dezfuli, F., et al., "Eicosapentaenoic acid and sulphur substituted fatty acid anolagues inhibit the proliferation of human breast cancer cells in culture," Breast Cancer Res Treat (1997), 45(3):229–39
• Mori, Y., et al., "Influence of highly purified eicosapentaenoic acid ethyl ester on insulin resistance in the Otsuka Long- Evans Tokushima Fatty rat, a model of spontaneous non-insulin-dependent diabetes mellitus," Metabolism (1997), 46(12):1458–64
• Hashimoto, N., et al., "[Effects of eicosapentaenoic acid in patients with bronchial asthma]," Nippon Kyobu Shikkan Gakkai Zasshi (1997), 35(6):634–40
• Adams, P.B., et al., "Arachidonic acid to eicosapentaenoic acid ratio in blood correlates positively with clinical symptoms of depression," Lipids (1996), 31 Suppl:S157-61

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