Hydration

The "drink eight glasses a day" rule has no real origin in the physiology literature, and the actual water-intake research is more interesting and more individual than that number suggests. These pieces cover what hydration research actually supports, and what it doesn’t.

Stylised water droplet made of overlapping measurement rings
ScienceHydration

How Much Water Should You Actually Drink?

The 'eight glasses a day' rule has no real origin in the physiology literature. Here's what actually determines your water needs.

Guideline

Related from elsewhere on the site

Stylised coffee cup with a water-droplet outline overlapping it, showing equal fill levels
Myth vs FactHydration

"Coffee dehydrates you"

At normal intake, coffee's mild diuretic effect is offset by its own fluid volume — a controlled trial found no hydration difference between coffee and water drinkers.

Myth