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【bio-news】核桃要比橄榄油更利于心脏健康
Walnuts May Beat Olive Oil for Heart Health
10.09.06, 12:00 AM ET
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.
More information
More on the nutritional benefits of walnuts is found on the FDA's Web site 认领了 整理完成向sina投稿
据美国每日健康新闻十月九日报导，西班牙研究人员发现，核桃比橄榄油更有利于心血管健康。
24名成人参加了实验，他们的血脂水平从正常到中度增高不等。午餐包括意大利香肠、奶酪三明治及高脂酸奶。餐后12人给予五茶匙橄榄油，另12人给予40克核桃。随后的超声检查显示，食用核桃组的血管更柔韧、更有弹性。
研究组带头人Ros教授称，这项研究阐明了核桃的作用机理。核桃和橄榄油均可降低高脂饮食后血管炎症及氧化发生，但核桃还可以保护血管的柔韧性，而橄榄油不能。这是因为核桃中含有与鱼体内ω-3脂肪酸化学结构相同的α-亚麻酸。他们的研究成果将于十月十七日发表于〈〈美国心脏病学会志〉〉。
美国心脏协会等权威机构号召美国人一周至少吃两次鱼，特别是富含ω-3脂肪酸的鱼。ω-3脂肪酸可以增加血中高密度脂蛋白浓度，使血管保持通畅。但Ros教授指出，鱼并不象核桃那样容易购买、食用方便，而且植物来源的亚麻酸用之不尽，相反鱼类资源正在逐渐枯竭。
迄今为止FDA尚未正式承认核桃可以降低心血管疾病风险。他们声称，虽然有证据支持作为低饱和脂肪及低胆固醇饮食的一部分，每天食用1.5盎司核桃可以降低冠心病风险，但是还缺乏决定性研究结果来证明这一点。
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作者:admin@医学,生命科学 2011-09-17 17:16
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