牛奶喝得越多不一定越有益

Children who drink more milk do not necessarily develop healthier bones, researchers said on Monday in a report that stresses exercise and modest consumption of calcium¹-rich foods such as tofu and broccoli². 

　　Appearing in the journal Pediatrics, the report drew its conclusions from previously³ published studies and was written by researchers from the Physicians Committee for Responsible Medicine, which advocates a strict vegetarian⁴ diet. 

　　"Under scientific scrutiny⁵, the support for the milk myth crumbles⁶. This analysis of 58 published studies shows that the evidence on which U.S. dairy intake⁷ recommendations are based is scant," said study author Dr. Amy Lanou in a statement. 

　　Some earlier studies that extol⁸ dairy products as a calcium source have been funded at least in part by the dairy industry. 

　　The U.S. government has gradually increased recommendations for daily calcium intake, largely from dairy products, to between 800 and 1,300 milligrams to promote healthy bones and prevent osteoporosis. 

　　But the Physicians Committee’s report said boosting consumption of milk or other dairy products was not necessarily the best way to provide the minimal⁹ calcium intake of at least 400 milligrams per day. Other ways to get the absorbable calcium found in one cup of cow’s milk include a cup of fortified¹⁰ orange juice, a cup of cooked kale or turnip¹¹ greens, two packages of instant oats, two-thirds cup of tofu, or 1-2/3 cups of broccoli, the report said. 

　　Several of the studies, which examined such factors as bone density¹² and rate of fractures, concluded that exercise may be more important than increased calcium consumption in developing strong bones. 

　　Data was scarce on the effect of calcium intake for children younger than 7 years, the report said. Dairy products provide 18 percent of the total energy and 25 percent of the total fat intake in the diets of American children, who are developing increasing rates of obesity¹³, it said. 

　　In an editorial in the journal commenting on the report, Frank Greer, a pediatrician at the University of Wisconsin in Madison, said the ideal way to achieve the goal of healthy bones is to make sure children exercise and consume up to 1,300 milligrams a day of calcium.

　　美国的一些研究人员日前在一份报告里说，儿童牛奶喝得越多，不一定就对骨骼越有益；运动以及食用适量的富含钙的食品（如豆腐）会促进儿童骨骼发育。 
　　据路透社3月7日报道，此前，美国政府不断劝告人们，每天食用奶制品可以增加身体对钙的摄取量；儿童如果每天能吸收800到1300毫克的钙元素，就能提高骨骼健康、防止骨质疏松症。然而，根据这份发表在《儿科学》期刊上的研究报告，增加牛奶和其它奶制品的食用量不一定是满足身体每天至少400毫克钙需求量的最好方式。 
　　这份报告的作者是华盛顿医学医师委员会的一些研究人员。他们重新研究了37篇关于（7岁以上儿童）钙的摄取对骨骼密度影响的论文，发现27篇论文不支持喝更多牛奶能吸收更多钙的说法。有几篇论文认为，锻炼比提高钙的摄取量更有助于强化骨骼。但是，目前缺乏关于7岁以下儿童摄取钙的效果的数据。 
　　研究报告说，儿童通过喝1杯牛奶里所摄取到的能吸收的钙，可通过喝一杯强化橙汁、一杯煮熟的羽衣甘蓝、两包速溶麦片、三分之二杯豆腐或者一杯半多的椰菜等也都可以摄取到。对于那些逐渐肥胖的美国儿童来说，奶制品提供了18％的热量和25％的脂肪。 
　　研究小组的组长艾米·Lanou在报告里说：“现在能得到的证据无法证实以前的营养指导：多喝牛奶或多食用奶制品能促进儿童和青少年骨骼发育。”在这份报告的注解里，美国威斯康星大学的儿科医师弗兰克·Greer说，使骨骼发育健康的理想方法是，让孩子锻炼并且每天最多摄取1300毫克的钙。而要获取这么多的钙，最简单的方法是食用低脂奶制品；低脂奶制品中含有对人体很有价值的维生素D，又是通常别的食物中所没有的。