Most Americans have heard that they should drink eight glasses of water a day to stay hydrated, but there is surprisingly little data to support this advice.
大多数美国人都听说过，每天必须喝八杯水，以保持身体水分，但是令人意外的是，几乎没有数据支持这一建议。
But now, a new “beverage hydration index” provides evidence-based suggestions for how to most efficiently hydrate. The index was developed from a British study published in December that tracked how long 13 common beverages remain in the body after being consumed.
但是现在，一种新的“饮料水分指数”为如何最有效地补水提供了以事实为依据的建议。这一指数是根据英国去年12月公布的一项研究开发出来的。这项研究追踪了喝下13种常见饮料后，它们在身体里停留的时长。
“In the last 25 years, we’ve done many studies on rehydration after exercise,” said Ronald J. Maughan, a hydration expert from Loughborough University, and lead author of the study. “We thought it was time to look at hydration in typical consumers who aren’t exercising.”
“在过去25年里，我们做了很多关于运动后补水的研究，”这项研究的主要作者、拉夫伯勒大学(Loughborough University)研究补水的专家罗纳德·J·莫恩(Ronald J. Maughan)说，“后来我们想，应该研究一下没有在运动的典型消费者的补水情况。”
The hydration index is modeled after the well-known glycemic index, which measures how the body responds to the carbohydrate content of different foods. (The glycemic index is used to help individuals keep their glucose-insulin response under control.) The guiding principle behind the new hydration index is that some fluids last longer in your body than others, providing more hydration. After all, if you drink a cup of water and then immediately excrete half that amount in your urine, you haven’t added 8 ounces to your water supply, but only 4.
补水指数是仿效著名的血糖指数设计的，它测量身体对不同食物的碳水化合物的反应（血糖指数用于帮助个人控制葡萄糖胰岛素反应）。新的补水指数的指导原则是，有些液体比其他液体在身体里留存的时间更长，补水效果更好。毕竟，如果你喝了一杯水，然后很快通过尿液排出一半水分，那么你其实没有补充8盎司水，而是只补了4盎司。
The British study determined the hydration index of 13 common beverages by having the participants, 72 males in their mid-20s, drink a liter of water as the standard beverage. The amount of water still remaining in subjects’ bodies two hours later — that is, not voided in urine — was assigned a score of 1.0. All other beverages were evaluated in a similar manner, and then scored in comparison to water. A score higher than 1.0 indicated that more of the beverage remained in the body as compared to water, while a score lower than 1.0 indicated a higher excretion rate than water.
英国的这项研究确定了13种常见饮料的补水指数。72名25岁左右的男性参与者喝下1升水作为基准。两小时后依然留存在参与者体内的水分含量（也就是没有通过尿液排出的水分）被指定为1.0。所有其他饮料以类似的方式进行评估，然后与水比较进行评分。得分高于1.0的饮料的体内水分留存率高于水；得分低于1.0的饮料的排泄率高于水。
The results showed that four beverages — oral rehydration solution, like Pedialyte; fat-free milk; whole milk and orange juice — had a significantly higher hydration index than water. The first three had hydration index scores around 1.5, with orange juice doing slightly better than water at 1.1. Oral rehydration solutions are specifically formulated to combat serious dehydration such as that resulting from chronic diarrhea.
结果表明，有四种饮料的补水指数比水高得多，它们分别是口服补水溶液，比如电解质液体；脱脂牛奶；全脂牛奶和橙汁。前三种的补水指数在1.5左右，橙汁的指数略高于水，为1.1。口服补水溶液是为对抗严重脱水设计的，比如因为慢性腹泻导致的脱水。
“It’s a very clever, even brilliant study,” said Lawrence Armstrong, a hydration expert at the University of Connecticut and immediate past president of the American College of Sports Medicine. “It assumes that water is the optimal rehydration fluid, which is biologically correct, and then compares other fluids to water.”
“这是非常聪明的研究，”康涅狄格大学(University of Connecticut)的补水专家、美国运动医学院(American College of Sports Medicine)刚离职的主席劳伦斯·阿姆斯特朗(Lawrence Armstrong)说，“它假定水是最理想的补水液体——从生物学角度讲是这样的——然后把其他液体与水进行比较。”
作者: kobe 时间: 2016-7-11 08:18
Why is milk so efficient at rehydration? “Normally when you drink, it signals the kidneys to get rid of the extra water by producing more urine,” Maughan said. “However, when beverages contain nutrients and electrolytes like sodium and potassium, as milk does, the stomach empties more slowly with a less dramatic effect on the kidneys.”
为什么牛奶在补水方面如此有效？“通常情况下，喝饮料意味着肾要通过制造更多尿液来去除多余的水分，”莫恩说，“不过，如果饮料中包含钠和钾等营养素和电解质，就像牛奶那样，那么胃的排空速度更慢，对肾的影响不那么剧烈。”
Perhaps surprisingly, drinks containing moderate amounts of caffeine and alcohol or high levels of sugar had hydration indexes no different from water. In other words, coffee and beer are not dehydrating, despite common beliefs to the contrary, and regular soda can hydrate you just as well as water.
也许令人意外的是，包含适量咖啡因和酒精或高水平糖分的饮料与水的补水指数没有差别。换句话说，咖啡和啤酒并不会让人脱水——尽管这与人们通常的看法相反——另外，普通汽水的补水效率和水一样。
“It’s true that caffeine is a diuretic, but not at the concentration found in most coffee drinks,” Maughan said. “When we are thirsty, drinking normal tea, coffee or cola helps to rehydrate us. The exceptions are very strong coffee drinks or strong alcoholic drinks like distilled spirits.”
“咖啡因的确是利尿剂，不过大部分咖啡饮品中的咖啡因浓度达不到这个效果，”莫恩说，“我们口渴时，喝正常的茶、咖啡或可乐能帮助我们补充水分。非常浓的咖啡或酒精饮料，比如蒸馏酒，是例外。”
The hydration index could prove useful when making decisions about what beverages to consume and when. For example, if you’re going on a long drive and won’t have access to fluids (or to bathrooms), you’d be smarter to drink milk with its high hydration index rather than water or iced coffee. But don’t forget that milk has many more calories than water, so don’t overdo it, either.
在决定何时喝何种饮料时，补水指数可能被证明是有用的。比如，如果你长时间开车，无法得到很多液体（也不能常去厕所），那么喝牛奶比喝水或冰咖啡更好，因为它的补水指数较高。不过，不要忘记，牛奶的热量比水高，所以也不要喝得过多。
While severe dehydration is rare except in heavy exercise, extreme environments and disease, studies have shown that heat and dehydration can contribute to increased mortality rates during hot weather. “Mortality increases sharply during heat waves, mostly because people don’t drink enough to compensate for their increased fluid losses,” Maughan said.
虽然严重脱水是剧烈运动、极端环境或患病情况下的罕见例外，但是多项研究表明，在高温天气下，高温和脱水可能导致死亡率升高。“在热浪来袭时，死亡率猛烈升高，主要是因为人们没有摄入足够的水分，以弥补增加的水分流失，”莫恩说。
Armstrong noted that in hot weather, it’s important to monitor your hydration status throughout the day. He suggested paying attention to your thirst, and drinking when necessary. Also, if your urine color is a dark yellow, it’s time for a refreshing drink.
阿姆斯特朗指出，在高温天气里，全天监测身体的水分状态很重要。他建议注意口渴状况，在需要时补水。另外，如果你的尿液颜色是深黄色的，你就需要喝点清爽的饮料。
