July 23rd, 2013

The Myth of 8 Glasses a Day

WaterWater is absolutely essential for life and an adult’s body is about 60% water by weight. The average person won’t last more than a few days without water,  although most can survive weeks or months without food. We consume water through food and drink, and a little water is also created inside the body through the metabolism of food.

Few would dispute that water is the very best beverage a person could drink. It’s just about free (if it comes out of the tap), it has no salt, sugar, fat or calories and it is very thirst-quenching. Surely, access to fresh, clean water is a human right.

And yet, I am compelled to argue that water-drinking sometimes goes too far, and the “8 glasses a day” slogan should be retired.  Where does “8 glasses a day” come from and how much water do we really need?

The current obsession with water began with the weight loss craze of the ‘60s and ‘70s. Drinking water was a way to “fill up” and keep hunger at bay. “8 glasses a day” was the essential companion to a strict low-calorie diet. It also became another yardstick by which to judge one’s success or failure, often resulting in guilty feelings. Today, the obsession is bolstered by the savvy marketing of bottled water companies. Water is now a huge business, accounting for billions of dollars in sales (but creating billions of plastic bottles, most of which litter the planet or languish in dumps).

Our actual water needs are defined by the National Academies of Science, publishers of the Dietary Reference Intakes. These science-based guidelines state women need approximately 2.7 litres (about 12 cups) of water per day and men need 3.7 litres (16 cups).  These guidelines are for water, but it is important to recognize that water is found in all fluids and most foods. Coffee, tea, milk, juice and soup provide water and, contrary to popular belief, coffee and tea are not dehydrating.  Juicy fruits such as melons are 90% water and even dry foods, such as bread, contain moisture. In fact, solid food is estimated to provide about 20% of our water needs, contributing roughly 2 cups for a woman and 3 cups for a man.

My bottom line? Enjoy water as part of your daily fluid needs. Do not feel compelled to drink any specific amount of water. All beverages count. If you are managing your weight choose lower calorie beverages (plain coffee, tea and low fat milk/milk alternatives) and avoid high-sugar, low-nutrient pop and other flavoured drinks.

Note: Older people may not always feel thirsty so should make an effort to drink regularly. People with kidney stones may need to drink extra water and should discuss this with their physicians.


Barbara Allan, 
Registered Dietician
Certified Diabetes Educator

2 thoughts on “The Myth of 8 Glasses a Day

  1. Sana says:

    well said…
    i would conclude one more point that drinking water more than ur body neeed may agreviate ur b.p , if ur a hypertensive patient, in case.
    so water intake must b according to ur
    1- body neeed
    2- habbit
    3- and if u feeel its less than u should have , than take it more to have
    * healthy skin
    * remove access amino acids from body
    * in case of kidney stones

    take water sips more frequently is a gud habbit

  2. Anne says:

    In my twenties I suffered with kidney stones. 8 of them to be exact. My Urologist suggested I drink a minimum of 8 glasses of water each day to avoid every forming stones again. I have followed his advice and its been 25 years since I have had one.

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