“Drink 8 glasses of water a day” is one of those bits of wisdom that everyone knows but no one seems to know why eight is the magic number. “Eight glasses a day” is like “finish your broccoli,” advice we’ve heard from our parents since we were kids and still mostly ignore.

drinking water
How much? It depends. Gauge your body to know if you’re getting enough of the good stuff.

But there’s good reason to listen up: 70-75% of an adult’s body weight comes from water, according to the Institute of Medicine (IOM). So, it’s pretty obvious how important water is to a healthy body.

But why 8 ounces 8 times a day? And what does that much water do? Knowing the details may encourage you to fill up and drink down.

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First, know that 64 ounces (what that recommendation totals to) is kind of arbitrary, an approximation based on national data showing the average daily water consumption of women and men who appear to be adequately hydrated, according to a report from the IOM. Ultimately, the 8-glasses recommendation reflects a very general guideline that is used because, well, it’s easy to remember.

“Water needs vary from person to person,” says nutritionist Lisa R. Young, PhD, RDN, a professor of nutrition at New York University and author of Finally Full, Finally Thin. “Various factors will affect how much water you need per day, including your activity level, environment, the season, diet, gender, personal health (diabetics need more water), and even medications.”

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Dr. Young advises her clients to count their glasses but also monitor their bodies, beyond just thirst, for clues that they are not drinking enough water. Knowing how your body functions when well-hydrated can help you recognized when your water tank is getting low. So what happens when you are drinking “enough” water? Read on to find out what experts and science says, and for more water news, don’t miss Ways to Make Sure Your Water is Safe to Drink.1

You’ll keep cool and avoid heat fatigue.


The water you drink provides the moisture in your skin that regulates your body temperature. As your sweat evaporates, your body cools, improving your ability to tolerate heat stress, according to a report in the International Journal of Sports Medicine.

You may improve your exercise performance.

protein water

Drinking water throughout your day can pay off when you get competitive. When your body has received that flood of 64 ounces of fluid, it just functions better. Adequate water supplies shuttle to every part of your body, including your muscles, which will contract optimally, just what you need for a rocket-powered serve in tennis or top execution in virtually any sport. By contrast, when inadequately hydrated, your greedy blood vessels pull water from your muscles to protect blood circulatio

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n. When that happens, exercise and sports performance suffer. Even just a loss of sweat equal to 2% of your body weight can cause noticeable decreases in physical and mental performance. Losing 5% or more of body weight through sweat during physical activities may decrease your muscles’ capacity for work by about 30%, according to Asker Jeukendrup, PhD, and biochemist Michael Gleeson, PhD in their Human Kinetics book Sport Nutrition.

Source: Eat This, Not That

It is recommended that we drink .5 oz for every pound that we weight. So, if you weigh 200 lbs, you should drink 100 ozs – approximately three liters of water.

Do you drink enough water to keep you hydrated and healthy? Comment below on what type of water you drink – tap, spring, filtered, etc – and why you drink it. Thanks!

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Ericka Scott

I was diagnosed with Type 2 Diabetes in 2000. Since then, I've been on a mission to help myself and loved ones living with Diabetes and High Blood Pressure, to prepare healthy and TASTY meals. Now, I'm here to help YOU do the same!


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