Eight glasses of water a day excessive for most people, study suggests
‘One size fits all’ guidance could lead to drinking water being wasted.
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A recommendation to drink eight glasses of water a day is likely to be excessive for most people, according to scientists.
The suggestion has become accepted wisdom and often appears in health guidance. The latest work, however, the most rigorous study to date on water turnover, reveals that people have a wide range of water intakes. Many people only require about 1.5 to 1.8 litres a day, lower than the two litres typically recommended.
“The current recommendation is not supported scientifically at all,” said Yosuke Yamada of the National Institute of Biomedical Innovation, Health and Nutrition in Japan, and one of the paper’s first authors.
One issue is that previous estimates of water requirements have tended to ignore the water content of food, which can contribute a substantial proportion of our overall intake. “If you just eat bread and bacon and eggs you will not get much water from food, but if you eat meat, vegetables, fish, pasta and rice you can get about 50% of your water needs from food,” said Yamada.
The study, published in the journal Science, assessed the water intake of 5,604 people aged between eight days and 96 years old from 23 countries.
Those living in hot and humid climates and at high altitudes as well as athletes and pregnant and breastfeeding women need to drink more water.
Prof John Speakman of the University of Aberdeen, a co-author, says: “I think it’s a recommendation that many people just ignore and follow what their body is telling them.”