Having to lose water from your body all day, every day is a fact of life. Even while you’re sleeping, you’re losing water. The weather, the temperature, your environment and activity levels, among other factors, affect how quickly you lose water. In order to stay healthy and thrive, you have to replace it.

Most of us need around 8 eight-ounce glasses of water every day, which equates to about 2 liters.

But why? What exactly is all of that water doing for us? We take a look at hydration from the scientist’s point of view!

1. During sports or intense exercise, your performance is intrinsically linked with your hydration levels. Even mild dehydration can have a …