Is“eight glasses of water a day”really scientific?“每天八杯水”真的科学吗?

陈福金

A famous health tip says youd betterdrink eight glasses of water （about twoliters） a day. However， the results of a newstudy suggest that less is needed.

An international group led by scien?tists at the Shenzhen Institute of AdvancedTechnology （SIAT） in China found that theaverage daily water intake of a man in histwenties should be 1.5 to 1.8 liters， whileit should be 1.3 to 1.4 liters for a female inthe same age group.

The researchers investigated 5，604participants from the ages of 8 days old to96 years old and from more than 20countries， using isotope⁃tracking methods.They have found that a man aged 20 to 35consumes 4.2 liters of water each day，while a woman aged 30 to 60 consumes3.3 liters， with the water requirementsdropping as he or she ages.

Since metabolism （ 新陈代谢） andwater exchange on skin can provide 15 percent， while food and drinking contri⁃bute half each of the remaining 85percent， people are thus suggested to drinkless than 45 percent of the total dailyturnover， according to the researchers.

“The majority of people perhaps donthave to drink 8 glasses of water a day，”said Zhang Xueying， co⁃first author of thepaper and an assistant research fellow atthe SIAT.

The total water input and outputvaries according to multiple factors，including body size， physical activity，air temperature， humidity， and altitude，according to the study.

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Do you really need to drink eightglasses of water a day？ Please calculatehow much water you need a day accordingto the text.