How Much Water Should You Drink Per Day?

The body is about 60% water, give or take.

We’re constantly losing water from our bodies, primarily via urine and sweat.

There are many different opinions on how much water we should be drinking every day.

The health authorities commonly recommend eight 8-ounce glasses, which equals about 2 liters, or half a gallon.

This is called the 8×8 rule and is very easy to remember.

However, there are other health gurus who think we’re always on the brink of dehydration and that we need to sip on water constantly throughout the day… even when we’re not thirsty.

As with most things, this depends on the individual and there are many factors (both internal and external) that ultimately affect our need for water.

I’d like to take a look at some of the studies on water intake and how it affects the function of the body and brain, then explain how to easily match water intake to individual needs.

Can More Water Increase Energy Levels and Improve Brain Function?

Many people claim that if we don’t stay hydrated throughout the day, our energy levels and brain function can start to suffer.

There are actually plenty of studies to support this.

In one study in women, a fluid loss of 1.36% after exercise did impair both mood and concentration, while increasing the frequency of headaches (1).

There are other studies showing that mild dehydration (1-3% of body weight) caused by exercise or heat can negatively affect many other aspects of brain function (2, 3, 4).

However, keep in mind that just 1% of body weight is actually a fairly significant amount. This happens primarily when you’re sweating a lot, such as during exercise or high heat.

Mild dehydration can also negatively affect physical performance, leading to reduced endurance (5, 6, 7).