Omega-3 Polyunsaturated Fatty Acids

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Omega-3 fatty acids are one of the two major families of polyunsaturated fatty acids (PUFA) that are essential to human health and development. (The other family are the omega-6 PUFA.) Omega-3 PUFA are mainly obtained from the diet, primarily from plants (especially flax seed, soy, and nuts), but also from cold-water fish, and to a lesser extent from diary products and eggs.

In recent years, two particular omega-3 PUFA - eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) - have been strongly associated with a reduced risk of certain cardiac problems.

EPD and DHA are found primarily in fish oil.

People who consume high levels of EPA and DHA appear to have a lower risk of sudden cardiac death from arrhythmias, as well as a reduced risk of atrial fibrillation, lower triglyceride levels, higher HDL cholesterol levels (the "good" cholesterol), and reduced blood pressure. Long-term ingestion of EPA and DHA may reduce the risk of acute coronary syndrome in people who have coronary artery disease.

How Much Omega-3 Is Enough?

A typical Western diet includes enough omega-3 PUFA to support the essential functions of life. For many people, dietary omega-3's come from soy, nuts or eggs, but for the most part these omega-3 PUFA are alpha-linolenic acid, and not EPA and DHA.

If you want to reduce your cardiac risk with omega-3 PUFA, you should make sure you’re getting enough EPA and DHA. And that means eating fish, or taking fish oil supplements. From current information, EPA plus DHA in the amount of 250 mg/day (total) is needed to get the cardiac benefit.

Some nutritional experts say that everyone should be getting extra omega-3 PUFA, whether they are trying to reduce their cardiac risk or not, because (they believe) the omega-3’s are needed to counterbalance the large amounts of omega-6 PUFA we consume in the typical Western diet. According to this view, unbalanced dietary omega-6 PUFA may actually increase our risk of health problems.

The omega-3 PUFA apparently help to mitigate such risk.

You can get the recommended amount of EPA and DHA by eating one or two servings per week of oily fish. Or, you can usually get enough EPA and DHA by taking about 1 gram per day of a fish oil supplement. (Since fish oil supplements come in many different formulations, read the label to find out how much EPA plus DHA is present in each capsule.)

What About Mercury?

A lot of concern has been expressed recently about the dangers of mercury contamination in fish. So how does this affect your ability to obtain the omega-3 fatty acids you need to reduce your cardiac risk?

In fact, only large predator fish contain enough mercury to be of concern. These include albacore tuna, king mackerel, swordfish, shark and tilefish. A few servings per week of almost any other kind of fish - in particular, shrimp, light canned tuna, salmon, pollock and catfish - should not expose you to any appreciable levels of mercury.

(Most fish sandwiches and fish sticks contain pollock.)

The large predatory fish species are almost never used to produce fish oil supplements, and then only in specialty products. Furthermore, any mercury present in fish is bound to fish protein (that is, it is in the muscle), and almost none is present in fish oil. As a result, fish oil supplements contain virtually no mercury.


Balk, EM, Lichtenstein, AH, Chung, M, et al. Effects of omega-3 fatty acids on serum markers of cardiovascular disease risk: a systematic review. Atherosclerosis 2006; 189:19.

Mozaffarian, D, Rimm, EB. Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA 2006; 296:1885.

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