Drinking water is the easiest thing you can do for your brain, but most people don’t drink anywhere near enough.

Fact: About 80% of the brain is comprised of water. If you don’t drink enough—or if you drink a lot of dehydrating liquids, such as coffee or alcohol—you’re going to struggle to think clearly and you may have memory problems. That’s because dehydration increases stress hormones, and stress hormones interfere with cognitive abilities.

Recommended: Drink half your weight in water ounces every day. Example: If you weigh 150 pounds, you’ll want to drink 75 ounces of water a day. Drink more during the warm months or if you exercise regularly and lose water in perspiration.