Although scientists are still discovering a wide range of beneficial effects of omega-3 fatty acids -- a type of polyunsaturated fat -- most of the evidence so far has been linked to the prevention of heart disease.
The Nutrition Source from the Harvard School of Public Health (http:// www.hsph.harvard.edu/) offers a great explanation of omega-3s. First and foremost, they are an essential part of cell membranes throughout the body. They help membranes' receptors do their work, and help regulate blood clotting, inflammation, and the function of artery walls.
In a recent issue of the Journal of the American Medical Association, researchers measured blood levels of omega-3 fatty acids and the length of telomeres -- structures at the ends of chromosomes that get shorter every time a cell divides -- in about 600 heart disease patients over five years. Shorter telomeres are a marker of "biological age" and are an indicator of less-healthy cells. The researchers found that patients with a higher blood level of omega-3s had longer telomeres; they believe this may be one reason why omega-3s are associated with heart health. Other research indicates that omega-3s help the heart by decreasing the risk of abnormal heartbeats, which can lead to sudden death; decreasing triglyceride levels; slowing the growth rate of atherosclerotic plaque; and lowering blood pressure, at least a bit.
Omega-3s may help control other conditions, as well. Another recent study, this one in the American Journal of Clinical Nutrition, linked the risk of age-related macular degeneration, the leading cause of blindness in older adults, with lower consumption of omega-3s, particularly the types that come from fatty fish: docosahexaenoic acid (DH A) and eicosapentaenoic acid (EPA).
The third type of omega-3 is alpha-linolenic acid (ALA), which is found in vegetable oils, particularly canola and soybean oil; nuts, especially walnuts; leafy green vegetables; flaxseed; and, sometimes, animal fat, especially from grass-fed animals. The body converts some ALA into DHA and EPA, but the best sources for the latter types are fatty fish such as salmon, mackerel, herring, lake trout, sardines, and albacore tuna.
The American Heart Association recommends eating at least two 3.5-ounce servings of fish per week, particularly fatty fish, to get enough omega-3s. It also suggests that people with coronary heart disease talk with their doctor about increasing intake of EPA and DHA, from food or supplements, to about 1 gram a day.
For information on omega-3 levels in a wide variety of foods, see the "Foods by Nutrient" listing on http://www.nutritiondata.com/ and search for foods highest in total omega-3 fats. The listing gives the estimated amount of omega-3s in 100 grams (about 3.5 ounces) of the foods listed.
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