Fact or Fiction? You Must Drink 8 Glasses of Water Daily

Do healthy people really need liquids even when they are not thirsty?

Virtually every health-conscious person can quote the recommendation: Drink at least eight eight-ounce glasses of water per day. Other beverages-coffee, tea, soda, beer, even orange juice-don't count. Watermelon? Not a chance.

There's no denying that water is good for you, but does everyone really need to drink 64 ounces or more every day? According to Heinz Valtin, a retired professor of physiology from Dartmouth Medical School who specialized in kidney research and spent 45 years studying the biological system that keeps the water in our bodies in balance, the answer is no.

Valtin says that for people who have specific health concerns, such as kidney stones or a tendency to develop urinary tract infections, drinking lots of water can be beneficial. But after an extensive search in 2002 for the origins of what is commonly referred to as the "8 x 8" guideline and a review of associated health claims, he reports finding no scientific evidence supporting the notion that healthy individuals need to consume large quantities of water. In 2008 Dan Negoianu and Stanley Goldfarb reviewed the evidence for the Journal of the American Society of Nephrology. They came to a similar conclusion: "There is no clear evidence of benefit from drinking increased amounts of water."

In fact, Valtin found that the 8 x 8 guideline may have originated from a misunderstanding. In 1945 the Food and Nutrition Board, now part of the National Academy of Sciences's Institute of Medicine, suggested that a person consume one milliliter of water （about one fifth of a teaspoon） for each calorie of food. The math is pretty simple: A daily diet of around 1,900 calories would dictate the consumption of 1,900 milliliters of water, an amount remarkably close to 64 ounces. But many dieticians and other people failed to notice a critical point: namely, that much of the daily need for water could be met by the water content found in food.

The Board revisited the question of water consumption in 2004. Its panel on "dietary preference intakes for electrolytes and water" noted that women who appear adequately hydrated consume about 91 ounces （2.7 liters） of water a day and men about 125 ounces （3.7 liters）. These seemingly large quantities come from a variety of sources-including coffee, tea, milk, soda, juice, fruits, vegetables and other foods. Instead of recommending how much extra water a person should drink to maintain health, the panel simply concluded that "the vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide."

真实的谎言：一天必须喝八杯水吗？

健康人即使不口渴也需要补充水分吗？

几乎每个关注健康的人都知道这样一条建议：每天至少饮八大杯8盎司玻璃杯的水。其它饮料，诸如咖啡 ,茶，苏打水，啤酒，甚至橙汁 还不计算在内。西瓜就更不包括了。

水确实对人有益。但人们真的每天需要喝至少六十四盎司的水？生理学专家海因茨。瓦尔汀认为情况并非如此。这位特茅斯医学院的退休教授专门从事肾脏研究，花了45年时间研究人体生物系统，看我们身体内的水分如何保持平衡。

瓦尔汀认为，对于患肾结石或者可能尿路感染，确实担心身体健康的人来说，多喝水有好处。但是在2002年对所谓" 8 × 8 "准则的源头经过广泛的追索和对健康产生影响的提法仔细审查后，他认定健康人也需要多喝水的提法缺乏科学依据。2008年丹。 尼戈亚卢（Negoianu）及史坦利。戈德法布在美国肾病学会 发表了对有关证据的评论。他们得出了类似的结论： "没有确切证据证明多喝水有利健康。 "

事实上，瓦尔汀发现， 8 × 8准则可能源于一种误解。1945年，食品和营养委员会（现在是美国国家科学院下属的医学研究所的一部分）提出，一个人消费一卡路里的食物需要1毫升的水（约五分之一茶匙）.很简单可以算出：一天吃饭吸收约1900卡路里意味着要引用1900毫升水，刚好等于64盎司。但许多营养师和有关人士忽略了一个关键点，即：人体每天所需的水分大多可由食物自身含有的水提供。

该委员会2004年重新审视了人体摄入水分的问题。其小组关于"饮食偏好摄入的电解质和水"指出，女性虽然看起来更"水灵",她们每天需要摄入约91盎司（ 2.7公升）的水，而男子每天约125盎司（ 3.7公升） .这些看似大量的水分其实来源广泛，包括咖啡，茶，牛奶，汽水，果汁，水果，蔬菜和其他食品。该小组并没有建议应该额外引用多少水才能保持健康，而是认为 "绝大多数的健康人感觉口渴才去喝水就足以充分满足他们的每天的水需求。 "