Dyerberg and group in 1978 reported in the Lancet, a health paradox that they noted in the Greenland Eskimos. The Eskimos, despite a high-fat diet, had a low rate of coronary heart disease. The researchers postulated that a protective effect was provided by the fatty oils present in their diet, rich in meat from seals, caribou and fish. Since then, this inverse relationship between fish intake and cardiovascular disease has become well established.

Fish oils are rich in omega-3 fatty acids. Along with omega-6 fatty acids, they are called polyunsaturated fatty acids (PUFAs). Both of these fatty acids cannot be synthesized by humans and are therefore considered 'essential'. Besides fish, omega-3 fatty acids are also found in walnuts, flaxseed, canola oil, broccoli, cantaloupe, kidney beans, spinach, grape leaves, Chinese cabbage, and cauliflower. Two omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are health and heart protective. A third kind, alpha-linolenic acid, is less potent. Omega-6 fatty acids are detrimental to heart health, and have been associated with depression. Omega-6 fatty acids are abundant in refined vegetable oils commonly used for cooking.

What is the link between fish oil intake and cardiovascular disease protection?

Several studies have shown an inverse relationship between fish consumption and coronary heart disease and death. In the DART study, 2003 men with a previous history of a heart attack were divided into two groups and monitored - one group had an increased fish oil consumption, either by diet or by supplementation compared to the other group, The increased fish oil group had a 29% reduction in death. Studied by Burr and group, this data was published in Lancet in 1989.

In a large GISSI-Prevenzione trial, 11,324 patients with a history of a heart attack were randomly assigned into groups; each group was given either 850 mg omega-3 fatty acid, 300 mg vitamin E, both, or neither. The results showed that the group given the fatty acid alone had a 45% reduction in sudden death and a 20% reduction in all-cause mortality. This was published in Lancet in 1999.

In a review of 11 studies, Markmann and Granbaek found that in populations at a higher risk of coronary heart disease, intake of 40-60 grams of fish per day could reduce the risk of death by 40%-60%. They published their data in the European Journal of Clinical Nutrition in 1999.

How do omega-3 fatty acids protect against heart disease?

Fish oils lower blood pressure and serum triglyceride levels. They also have anti-arrhythmic, anti-thrombotic, anti-atherosclerotic, and anti-inflammatory properties. They also improve endothelial function. All these effects protect against heart attacks from coronary heart disease and sudden death due to an irregular heart rhythm.

How much omega-3 fatty acids do you need?

It is recommended that the daily intake of omega-3 fatty acid be 2.85 g/day. Healthy marine sources are fresh tuna, sardines, salmon, herring, trout and oysters. Fish should be grilled, baked, or broiled -- not fried. Fried fish loses all of its benefits. This lack of benefit from fried fish was documented by Mozaffarian in the Cardiovascular Health Study published in Circulation in 2003. As noted earlier, omega-3 fatty acids are also found in walnuts, flaxseed, canola oil, broccoli, cantaloupe, kidney beans, spinach, grape leaves, Chinese cabbage, and cauliflower. Recently, omega-3 fatty acid enriched eggs have become available in the supermarkets and can help meet the daily requirements. If one is unable to eat enough fish or other food sources of omega-3 fatty acids, fish oil supplementation should be considered. The usual amount is 1 gm EPA and DHA per day, although your physician may recommend higher doses in certain situations.

Is fish safe?

Fish at the top of the food chain often contain significant levels of methylmercury, polychlorinated biphenyls, dioxins, and other environmental contaminants. These include mackerel, shark, swordfish, and tile fish (golden bass or golden snapper). The FDA advises pregnant women, women wanting to become pregnant, nursing mothers and children to avoid these fish as they may be at an increased risk of mercury intoxication.

Are fish oils safe?

In general, most fish oils sold over the counter in the USA are safe. The FDA in 1997 indicated that the consumption of up to 3 g EPA + DHA/day from all sources is safe for American adults. Fish oils do not interact with other drugs and usually have no side effects. Fishy aftertaste can be lessened by keeping the supplements in the freezer. Rarely nausea, bloating and belching can occur. Excessive intake may cause bleeding. There is only one FDA approved fish oil preparation in the USA. It is available by prescription under the trade name of Omacor. Because of a patented refining process, toxins such as mercury are completely removed, It also has more PUFAs - 90% compared with 60% in some commercially available products. This makes Omacor more reliable and efficacious.

Summary

The heart protective effects of omega-3 fatty acids are very compelling. These essential polyunsaturated fatty acids are abundant in fish and certain vegetables and nuts. People at a high risk of developing heart disease or who have established heart disease, should supplement their diet with fish oil capsules providing 1 gm EPA and DHA per day. It would be prudent to discuss this therapy with your physician.

Dr. Shashi K. Agarwal is a Board Certified Internist and Cardiologist with a private practice in New York City and New Jersey. He is also a diplomat of the American Board of Holistic Medicine and the American Academy of Anti-Aging Medicine.

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