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来源：http://sa.ylib.com/news/newsshow.asp?FDocNo=1593&CL=1
原文为繁体中文。
越来越多证据显示，碳水化合物对心脏的危害比脂肪更严重。 撰文╱穆易尔（Melinda WennerMoyer）
翻译╱林慧珍
少吃饱和脂肪，是美国政府在过去30年来不断向民众鼓吹的金科玉律。但从1970年以来，美国人已经很尽职地降低了饱和脂肪在每日摄取热量中所占的比例，但美国人肥胖的比率仍然增加了一倍多、糖尿病患是原来的三倍，心脏病也仍然是全美第一号杀手。现在，一连串新研究（包括一项对20多个研究的综合分析）对此提出了解释：研究人员可能弄错了凶手。现在美国人用以取代脂肪热量来源的碳水化合物加工食品，可能会增加肥胖、糖尿病与心脏病的风险，而且比脂肪 还危险。这项发现，将对美国预计在今年发表的新饮食指南产生重大影响。
今年3月《美国临床营养期刊》发表了一项综合分析，结合多项研究的数据，针对近35万人每天的摄食内容，以及他们在过去5~23年间罹患心血管疾病 的风险，进行比较。该项分析由美国儿童医院奥克兰研究所的动脉粥状硬化研究主持人克劳斯（Ronald M. Krauss）领导，并没有发现饱和脂肪的摄取量与心脏病风险有任何关联。
这个结果与最近几年的相关研究结论一致，推翻了过去的认知。传统观念认为，饱和脂肪对心脏有害，因为它会增加总胆固醇量，但克劳斯表示，这想法「大 部份是根据推断，没有研究数据的支持。」
哈佛公共卫生学院的营养与流行病学教授史丹普佛（Meir Stampfer）指出，过去这种推论的逻辑有一个问题，那就是「总胆固醇并非预测心脏病风险的有力指标。」虽然饱和脂肪会增加血液中「坏的」低密度脂蛋白（LDL）胆固醇，但同时也能增加「好的」高密度脂蛋白（HDL）胆固醇。2008年，史丹普佛与同事在《新英格兰医学期刊》发表了一项研究报告，他们 针对322名中度肥胖者进行为期两年的追踪研究，这些人要从以下三种饮食之中择一：根据美国心脏学会的饮食指南所设计的低脂、限制热量饮食；以丰富蔬菜及少量红肉搭配而成的地中海式限制热量饮食；以及低碳水化合物、但不限制热量的饮食。最后的结果显示，虽然食用低碳水化合物的受试者摄取的饱和脂肪含量最 高，但血液中HDL含量对LDL含量的比率却最符合健康，而且他们减轻的体重也是摄取低脂肪受试者的两倍。史丹普佛的研究结果显示，饱和脂肪其实并不是那么糟，而碳水化合物可能更危险。他与同事发表在1997年《美国医学会期刊》的研究指出，针对6万 5000名妇女进行检测发现，摄食最容易被消化吸收的碳水化合物（也就是升糖指数最高的食物）排名前1/5的妇女，得到第二型糖尿病的风险，比饮食升糖指
数最低的1/5高出47%以上（她们的脂肪摄取量则不影响罹患糖尿病的风险）。一项由荷兰研究人员在2007年发表于《美国心脏病学会期刊》的研究报告，
针对1万5000名妇女进行研究，发现摄取食物的血糖负荷（根据食物份量及其他因素计算而得）平均值排名前1/4的超重妇女，发生冠状动脉血管疾病的风
险，比最低的1/4超重妇女还高出79%。美国波士顿儿童医院肥胖研究计划主持人路德维（David Ludwig）表示，这种趋势可能有一部份是因为高升糖指数的碳水化合物对血糖产生的溜溜球效应，它会刺激脂肪生成及发炎反应，提高整体热量摄取量并降低
胰岛素的敏感度。
英文版
来源：
http://www.scientificamerican.com/article.cfm?id=carbs-against-cardio
From the May 2010 Scientific American Magazine | 114 comments Carbs against Cardio: More Evidence that Refined Carbohydrates, not Fats, Threaten the Heart
Whether the new thinking will be reflected in this year's revision of the federal dietary guidelines remains unclear
Eat less saturated fat: that has been the take-home message from the U.S. government for the past 30 years. But while Americans have dutifully reduced the percentage of daily calories from saturated fat since 1970, the obesity rate during that time has more than doubled, diabetes has tripled, and heart disease is still the country’s biggest killer. Now a spate of new research, including a meta-analysis of nearly two dozen studies, suggests a reason why: investigators may have picked the wrong culprit. Processed carbohydrates, which many Americans eat today in place of fat, may increase the risk of obesity, diabetes and heart disease more than fat does—a finding that has serious implications for new dietary guidelines expected this year.
In March the American Journal of Clinical Nutrition published a meta-analysis—which combines data from several studies—that compared the reported daily food intake of nearly 350,000 people against their risk of developing cardiovascular disease over a period of five to 23 years. The analysis, overseen by Ronald M. Krauss, director of atherosclerosis research at the Children’s Hospital Oakland Research Institute, found no association between the amount of saturated fat consumed and the risk of heart disease.
The finding joins other conclusions of the past few years that run counter to the conventional wisdom that saturated fat is bad for the heart because it increases total cholesterol levels. That idea is “based in large measure on extrapolations, which are not supported by the data,” Krauss says.
One problem with the old logic is that “total cholesterol is not a great predictor of risk,” says Meir Stampfer, a professor of nutrition and epidemiology at the Harvard School of Public Health. Although saturated fat boosts blood levels of “bad” LDL cholesterol, it also increases “good” HDL cholesterol. In 2008 Stampfer co-authored a study in the New England Journal of Medicine that followed 322 moderately obese individuals for two years as they adopted one of three diets: a low-fat, calorie-restricted diet based on American Heart Association guidelines; a Mediterranean, restricted-calorie diet rich in vegetables and low in red meat; and a low-carbohydrate, nonrestricted-calorie diet. Although the subjects on the low-carb diet ate the most saturated fat, they ended up with the healthiest ratio of HDL to LDL cholesterol and lost twice as much weight as their low-fat-eating counterparts.
Stampfer’s findings do not merely suggest that saturated fats are not so bad; they indicate that carbohydrates could be worse. A 1997 study he co-authored in the Journal of the American Medical Association evaluated 65,000 women and found that the quintile of women who ate the most easily digestible and readily absorbed carbohydrates—that is, those with the highest glycemic index—were 47 percent more likely to acquire type 2 diabetes than those in the quintile with the lowest average glycemic-index score. (The amount of fat the women ate did not affect diabetes risk.) And a 2007 Dutch study of 15,000 women published in the Journal of the American College of Cardiology found that women who were overweight and in the quartile that consumed meals with the highest average glycemic load, a metric that incorporates portion size, were 79 percent more likely to develop coronary vascular disease than overweight women in the lowest quartile. These trends may be explained in part by the yo-yo effects that high glycemic-index carbohydrates have on blood glucose, which can stimulate fat production and inflammation, increase overall caloric intake and lower insulin sensitivity, says David Ludwig, director of the obesity program at Children’s Hospital Boston.
Will the more recent thinking on fats and carbs be reflected in the 2010 federal Dietary Guidelines for Americans, updated once every five years? It depends on the strength of the evidence, explains Robert C. Post, deputy director of the U.S. Department of Agriculture’s Center for Nutrition Policy and Promotion. Findings that “have less support are put on the list of things to do with regard to more research.” Right now, Post explains, the agency’s main message to Americans is to limit overall calorie intake, irrespective of the source. “We’re finding that messages to consumers need to be short and simple and to the point,” he says. Another issue facing regulatory agencies, notes Harvard’s Stampfer, is that “the sugared beverage industry is lobbying very hard and trying to cast doubt on all these studies.” |
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发表于 2010-6-22 08:40:52
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