Somewhere along the way we all absorbed the idea that we must drink eight glasses of water a day or risk shrivelling up. It is one of those facts that everyone repeats and no one can source.
Where the number falls apart
The eight-glasses figure appears to come from a 1945 recommendation that we take in around two and a half litres of fluid a day. The part everyone forgot was the next sentence, which noted that much of that comes from food. Soup, fruit, vegetables, tea and coffee all count.
So the image of a person grimly working through a stack of water glasses on top of everything else they drink was never the advice. It was a misremembering.
A better guide
Your body has a remarkably good system for this. It is called thirst. For most healthy adults, drinking to thirst across the day does the job. A few practical signs are more useful than any target:
- Pale straw-coloured urine usually means you are fine
- Dark and infrequent suggests you could drink more
- Hot weather, exercise and illness genuinely raise your needs
Older adults can have a blunted thirst signal, so a bit more conscious sipping helps there. And yes, you can overdo it, though that is rare and usually involves extreme endurance events.
What I do now
I keep a glass on my desk and drink when I notice I want to. I have a glass with meals. I have stopped treating hydration as a daily exam I might fail. The eight-glasses rule made a simple bodily function feel like a chore, and it never needed to be one.