Fact or Fiction: You Should Drink 8 Glasses of Water Per Day

You've probably heard numerous times that you need to drink eight glasses of water a day to keep your body hydrated. Or if you can't reach eight, at the very least, you should aim for six. Maybe you have even heard of "8x8" as a short-hand term for eight glasses of eight ounces of water. Today, many fitness and health apps track your intake with the goal to reach 64 ounces daily. But how many people know where this number came from?

As it turns out, this number was established in the 1940s around the idea that drinking plenty of water could help the body flush out toxins. However, the science, like many things from the 1940s, may need a bit of an update.

We asked several experts to explain how to know if you're getting enough fluids and how to stay hydrated — and we asked them if eight glasses of water a day is still the gold standard for health.

The Origins of the Eight Glasses of Water Per Day Concept

The initial recommendation that everyone should drink eight, eight-ounce glasses of water per day originated with the United States Food and Nutrition Board in 1945. The recommendation was 2.5 liters of water per day based on a 2,000-calorie diet with "the idea that you need to flush out toxins with this amount of water," says New York-based registered dietitian and nutrition consultant Rachel Naar, M.S., C.D.N, R.D. But there isn't sufficient data to back up that specific number, despite the long-standing recommendation.

Plus, the gudiance included considering food sources as a way to get some of that daily water intake. Naar explains, "[There is] no strong consensus because there is not a lot of scientific evidence pointing to a conclusive answer; it's not based on any sound research, and the recommendation actually did state that most of the water could be from food sources."

Jodi Greebel, M.S., R.D.N., a registered dietitian nutritionist and nutrition consultant adds, "In short, not everyone needs six to eight cups of water per day, and the number is based on perpetuated myths — although I don't think it's a bad one."

To put it another way, every individual's true requirement for healthy hydration is different. "The amount of water each person needs is determined by many other factors including age, activity, and what else they consume," Greebel says. So you may not need to focus on drinking eight glasses of water per day, especially if you're drinking other beverages and eating plenty of fruits and vegetables.

Food Counts Toward Your Hydration Total

As important as plain ol' water is for our bodies, it isn't the only element capable of keeping us hydrated. Drinking other beverages, such as herbal teas, coffee, and even sports drinks, counts.

Even though coffee is a diuretic, Holly Klamer, M.S., R.D.N., a Michigan-based registered dietitian nutritionist says, "Caffeinated beverages are considered slightly dehydrating, but a moderate intake is not enough to deplete water from the body. They still provide fluid the body can use."

Although sugary drinks, like sports drinks and soda, do count toward liquid consumption, you want to think about the whole picture. Michael Hartman, Ph.D. in exercise physiology and VP of research and development at Plexus Worldwide, says, "When consuming other sources of fluids it is important to recognize calorie content and sugar intake as it relates to overall health."

Eating a varied diet with plenty of vegetables and fruits is also beneficial, and not only for all the vitamins, minerals, and nutrients. Consuming them can be another way to get enough fluids, as many of the most popular fruits and vegetables are more than 85 percent water.

"Many foods are hydrating and provide a tremendous amount of water, particularly if you are eating a diet high in fruits and vegetables. Cucumbers, grapes, watermelon, and many others can be up to 80 percent water. Broth-based soups, yogurt and popsicles all count towards water intake," says Greebel.

How to Know if You're Getting Enough Water

One of the best ways to quickly know if you've had enough water is to pick up on your body's signs that you're well hydrated — or the signs that you aren't. There are several hints to know that you're hydrated. "You drink proactively and don't feel thirsty; you urinate throughout the day, and the urine is a pale yellow color," Greebel says.

Indeed, your urine's color could tell you as much about your hydration status as the number of empty cups on your desk.

"A general rule of thumb to assess hydration throughout the day is to look at urine color," says Klamer. The color will provide insight on whether you need to drink more or if you're on the right track. "When urine is pale yellow to clear, that usually indicates you are hydrated. If urine color is yellow or darker, that probably means you need more fluids," she says.

You should know that color can be influenced by other factors, howevr. "Urine color can be affected after taking supplements, medications, and in other instances," explains Klamer.

You should always be on the lookout for signs that you could be dehydrated, too. "Some signs of dehydration include feeling thirsty — this means you are already dehydrated; fatigue, though this can be a sign of many things; dry lips and mouth; concentrated/dark color urine; not urinating often," explains Greebel.

Can You Drink Too Much Water?

With so much focus on drinking enough water each day, it may be hard to imagine that drinking too much water is possible — but it is. Naar says, "It is possible to over hydrate; however, it's pretty rare."

What happens to our bodies when we drink too much water? "I've personally experienced it, and you feel nauseated and dizzy, as a result," Naar explains, adding "Drinking too much can lead to water intoxication, or hyponatremia, which causes the inside of the cells to swell because of very low sodium levels in the bloodstream."

Another condition can result from over hydration. Hartman explains, "Drinking too much water can also result in hypervolemia, which is a medical condition in which too much fluid in the blood from excessive drinking can dilute the electrolytes."

Depending on how much water you drink and how quickly can also be bad for the body. Although kidneys are skilled at processing plenty of liquids, they do have their limits. "Kidneys can remove about 20 to 28 liters of water a day, but can't remove more than 0.8 to one liter per hour. Drinking more than this is dangerous!," says Naar.