Good hydrations: Do I need eight glasses of water a day?
来源：未知 作者：盛曲 时间：2019-03-03 08:07:04
Plainpicture By Graham Lawton It’s not called Adam’s ale for nothing. Water was presumably what our early ancestors drank, to the exclusion of everything else. If you stopped drinking it now you would be dead within a week. It is the only nutrient whose absence is lethal in so short a time. But how much you should drink is surprisingly contentious. It is common to hear eight glasses a day – about 2 litres – even if you don’t feel thirsty. In 2002, physiologist Heinz Valtin of Dartmouth Medical School in New Hampshire tried to track down the source of this advice. The closest he came was a 1974 book that casually advised six to eight drinks a day – not just water but also soft drinks, coffee, tea, milk and even beer. As for its scientific validity, Valtin found none. As the Food and Nutrition Board of the US National Academies of Science, Engineering and Medicine advises: “The vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide“. The only exception is some elderly people whose feedback mechanisms go awry, meaning they can become dehydrated without thirst. Generally, there is little to gain by doing more than just quenching your thirst. Water doesn’t remove toxins from the skin,