Why Drinking 8 Glasses of Water a Day Is Not Based on Science

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The '8 glasses of water a day' rule has no scientific basis — here's where it actually came from Do you still count your glasses, or do you just drink when you're thirsty?

Transcript

The 8-glasses rule? Turns out, nobody proved it. It traces back to a 1945 US recommendation — but it included water from food, too. Foods like cucumber and watermelon supply a meaningful chunk of your daily fluid — often around 20%. For most healthy adults, thirst is actually a reliable cue — your body signals before you're truly dehydrated. Here's the part nobody mentions — heat, heavy exercise, or illness can sharply raise your actual needs. Urine color is one of the most practical hydration checks — pale yellow generally means you're doing fine. Age, body size, climate, and activity all shift how much fluid you actually need — one number can't cover everyone. Follow for more everyday myths, unpacked with the real science.