No need to avoid healthy omega-6 fats

Omega-6 fats from vegetable oils — like their cousins, the omega-3 fats from fish — are good for the heart.

Omega, the final letter of the Greek alphabet, is often used to signify the last of something, or the end. When applied to dietary fats, though, omega represents a healthy beginning. Two families of polyunsaturated fats, the omega-3 and the omega-6 fats, are good for the heart and the rest of the body.

The terms omega-3 and omega-6 don't signify anything mystical. Instead, they describe the position of the first carbon-carbon double bond in the fat's backbone. This influences the shape of a fat molecule which, in turn, affects its function in the body.

The benefits of omega-3 fats from fatty fish and likely from plant sources like flaxseeds and walnuts are well known. They help protect the heart from lapsing into potentially deadly erratic rhythms. They ease inflammation. They inhibit the formation of dangerous clots in the bloodstream. They also lower levels of triglycerides, the most common type of fat-carrying particle in the blood.

Omega-6 fats, which we get mainly from vegetable oils, are also beneficial. They lower harmful LDL cholesterol and boost protective HDL. They help keep blood sugar in check by improving the body's sensitivity to insulin. Yet these fats don't enjoy the same sunny reputation as omega-3 fats.

The main charge against omega-6 fats is that the body can convert the most common one, linolenic acid, into another fatty acid called arachidonic acid, and arachidonic acid is a building block for molecules that can promote inflammation, blood clotting, and the constriction of blood vessels. But the body also converts arachidonic acid into molecules that calm inflammation and fight blood clots.

The critics argue that we should cut back on our intake of omega-6 fats to improve the ratio of omega-3 to omega-6s. Hogwash, says the American Heart Association (AHA). In a science advisory that was two years in the making, nine independent researchers from around the country, including three from Harvard, say that data from dozens of studies support the cardiovascular benefits of eating omega-6 fats (Circulation, Feb. 17, 2009). "Omega-6 fats are not only safe but they are also beneficial for the heart and circulation," says advisory coauthor Dr. Dariush Mozaffarian, an assistant professor of medicine at Harvard-affiliated Brigham and Women's Hospital.

It turns out that the body converts very little linolenic acid into arachidonic acid, even when linolenic acid is abundant in the diet. The AHA reviewers found that eating more omega-6 fats didn't rev up inflammation. Instead, eating more omega-6 fats either reduced markers of inflammation or left them unchanged. Many studies showed that rates of heart disease went down as consumption of omega-6 fats went up. And a meta-analysis of six randomized trials found that replacing saturated fat with omega-6 fats reduced the risk of heart attacks and other coronary events by 24%. A separate report published in the American Journal of Clinical Nutrition that pooled the results of 11 large cohorts showed that replacing saturated fats with polyunsaturated fats (including omega-6 and omega-3 fats) reduced heart disease rates more than did replacing them with monounsaturated fats or carbohydrates.

Good omega-6 fats and omega-3 fats for good health

The latest nutrition guidelines call for consuming unsaturated fats like omega-6 fats in place of saturated fat. The AHA, along with the Institute of Medicine, recommends getting 5% to 10% of your daily calories from omega-6 fats. For someone who usually takes in 2,000 calories a day, that translates into 11 to 22 grams. A salad dressing made with one tablespoon of safflower oil gives you 9 grams of omega-6 fats; one ounce of sunflower seeds, 9 grams; one ounce of walnuts, 11 grams.

Most Americans eat more omega-6 fats than omega-3 fats, on average about 10 times more. A low intake of omega-3 fats is not good for cardiovascular health, so bringing the two into better balance is a good idea. But don't do this by cutting back on healthy omega-6 fats. Instead, add some extra omega-3s.

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