Know your medical facts from myths? There are a lot of old wives' tales out there. But where do they come from and what is the truth? This week, do I really have to drink eight glasses of water a day?

What's the truth?

This myth is so pervasive and ingrained that doctors even pass it on to their patients.

Yet it's not true: there's not a single shred of evidence that suggests you need to drink that much water. In reality, we get most of the fluid we need from the food we eat.

Drinking 8 glasses of water
Illustration by David Humphries

 

Where did the myth come from?

It's thought that the first reference to the supposed need was made by the Food and Nutrition Board of America's National Research Council in 1945. Back then, they said that adults should consume four pints of water a day (about eight glasses).

They also said, however, that most of this would come from food. The first part stuck; the second part didn't.

 

So there's nothing to worry about?

It's still important to ensure that you're adequately hydrated, but slavishly sticking to eight glasses a day isn't a very helpful way to do it.

There are times when your body needs more fluid—when you're exercising heavily for example—and times when it needs less. The best way to keep track of whether you're hydrated enough is to check the colour of your urine.

If it's dark, drink more; if it's very dilute, you can drink less. The ideal colour is light straw coloured.

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