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Walnuts May Beat Olive Oil for Heart Health
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MONDAY, Oct. 9 (HealthDay News) -- A high-fat dinner followed by an unusual dessert suggests that walnuts might be even better for the arteries than olive oil, Spanish researchers report.
The dinner consisted of a salami and cheese sandwich on white bread, plus high-fat yogurt. The "dessert" consisted of five teaspoons of olive oil for half the diners and 40 grams of walnuts (about eight shelled nuts) for the other half.
Ultrasound examinations showed that the arteries of those eating the walnuts stayed more flexible and elastic after the fatty meal those of the folks who ate olive oil. The study's 24 adult participants had varying levels of blood cholesterol , ranging from healthy to moderately high.
"This study shows the mechanism for the beneficial effects of walnuts," contended study lead researcher Dr. Emilio Ros, director of the Lipid Clinic at Hospital Clinico in Barcelona.
Both olive oil and walnuts decrease the onset of inflammation and oxidation in the arteries after a high-fat meal, but walnuts preserve the blood vessels' flexibility while olive oil does not, according to Ros. He attributed much of the beneficial effect to the alpha-linolenic acid found in walnuts. This nutrient is similar to the omega-3 fatty acids found in fish.
The study, which was funded in part by the California Walnut Board, was expected to be published in the Oct. 17 issue of the Journal of the American College of Cardiology.
Ros points out that authorities such as the American Heart Association recommend that Americans eat at least two fish servings a week, preferable oily fish rich in omega-3 fatty acids. Omega-3s increase blood levels of HDL cholesterol, the "good" kind that helps keep arteries clear.
The only problem with that recommendation, Ros said, is that fish isn't as easy to buy and consume as walnuts. The alpha-linolenic acid in walnuts has the same chemical structure as omega-3 fatty acids, he noted, and "linolenic acid found in plant foods provide an inexhaustible supply, while fish are being depleted."
The California Walnut Board -- which has also funded several similar studies -- petitioned the U.S. Food and Drug Administration more than two years ago for its permission to formally claim that walnuts reduce the risk of heart disease.
So far, the FDA has only approved a "qualified health claim," which says that "supportive but not conclusive research shows that eating 1.5 ounces of walnuts per day as part of a low-saturated-fat and low cholesterol diet, and not resulting in increased caloric intake, may reduce the risk of coronary heart disease ."
For its part, the American College of Cardiology had the paper reviewed by Dr. Robert A. Vogel, professor of medicine at the University of Maryland. He issued a statement saying, "This demonstrates that the protective fat from walnuts actually undoes some of the detrimental effects of a high-saturated-fat diet, whereas a neutral fat, such as olive oil, does not have as much protective ability."
People who eat the so-called "Mediterranean diet " -- lauded by many nutritionists as heart-healthy -- believe that olive oil provides the major cardiac benefit, "but this research indicates that's not true," Vogel said. "There are probably other factors in the diet, including that it is a relatively rich source of nuts."
More research is needed to determine whether the protective effect of walnuts is affected by heating and cooking, or whether they are best eaten raw, he added.
SOURCES: Emilio Ros, M.D., Ph.D., director, Lipid Clinic, Hospital Clinico, Barcelona, Spain; Oct 10, 2006, Journal of the American College of Cardiology online; Oct. 9, 2006, news release, American College of Cardiology
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