Do You Really Need To Drink 8 Glasses Of Water Every Day?


There’s a lot of disagreement within the nutrition sphere, but there is one health claim that seems to withstand the test of time—the “8×8” rule. It’s widely held that we should be consuming 64 ounces of water per day, or eight eight-ounce glasses of water. But is there actually any research behind this recommendation? More importantly, how much water should we really be drinking each day? We decided to find out.

8×8 Rule: Fact or Fiction?

It’s thought that the water intake rule originated loosely from a recommendation made by the National Academy of Medicine in 1945—then called the Food and Nutrition Board. The organization advised that the average person should consume 1 mL of water for every calorie consumed. This equates to about 64 ounces a day on a 1,900 calorie diet—close to current USDA recommendation of 2,000 calories per day.

A large review of water intake-related studies found no scientific reports concluding this rule is as good as law. The author of this review actually found several studies noting the potential dangers of following the “8×8” recommendation.

Recommended Water Intake

As it turns out, there really isn’t a one-size-fits-all recommendation for water intake. While the current Dietary Reference Intakes advise approximately nine cups per day for women and 13 cups for men, fluid requirements can also vary based on age, activity level, and even your climate.

When it comes to drinking water, it’s best to just go with your gut. Drink when you’re thirsty and stop when you’re not. Keeping a reusable water bottle with you is an easy way to stay hydrated—and it can also help prevent you from filling up on soda or other sugary beverages. (Don’t worry, sparkling water counts toward your goal, too!)

Benefits of Drinking Water

The most important benefit of all, however, is that water keeps us alive. We can’t survive more than a few weeks without it.

How to Know If You’re Dehydrated

While intense thirst is the most obvious red flag, there are several other major signs that could mean you need to up that water intake. Because the brain is composed of 80 percent water, headaches are actually one of the first signs of dehydration. Dehydration can cause brain shrinkage, reduced oxygen and blood flow, and ultimately painful swelling and inflammation.

Can Drinking More Water Help You Lose Weight?

Ah, the age-old question. Lucky for us, the CDC does indeed tout water as a weight loss (and management) tool. Some studies have found links between water consumption and a metabolism boost, estimating that drinking two liters of water—just over 68 ounces—per day could lead to an additional 96 calories burned.

Our hydration status has an impact on our hunger cues, meaning we can often mistake hunger for thirst if we are dehydrated. Since some of our water intake comes from food, our brains can get tricked into thinking we’re hungry when we just need a big glass of H2O. Drinking water approximately 30 minutes before meal times can even help you consume fewer calories during meals.

Can You Drink Too Much Water?

Yes—and overconsumption of water can be a serious health risk. While uncommon, hyponatremia is a condition induced by excessive water consumption where blood sodium levels become too low. Symptoms of hyponatremia include brain fog, bloating, headaches, and nausea.