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Month’s Food For Thought






 September 2019


Myth of 8 Glasses of Water a Day


Do I need to drink 8 glasses of water a day?

No, you don’t.

But I thought I should do this to stay healthy?

There is no scientific proof that, for healthy people, drinking extra water has any health benefits. Scientific research has shown that drinking large amounts of water does not:

 Make skin look healthier or wrinkle free

 Benefit kidney function

 Clean out toxins

 Make you feel more energetic.

Where does the 8-glasses guideline come from?

In 1945, the U.S. Food and Nutrition Board recommended that people drink 2.5 liters (84.5 ounces) a day. Evidently, most who read this then ignored the following sentence, “Most of this quantity is contained in prepared foods.” Whatever “prepared” meant in 1945, all food contains water, especially vegetables and fruits.

How do I know when to drink?

The human body is beautifully designed to let you know you need to drink long before you are at risk of becoming dehydrated. Drink when you are thirsty. If you are doing strenuous work in a hot environment, you need to drink extra fluid to make up for what you lose through perspiration (sweat)

Use the color of your urine as a guide. Your urine should be light yellow. If it looks like water, you are drinking more than you need. If it is dark yellow or orange you need to drink more.

What should I drink?

Water is healthy. Sugared drinks like pop and sweetened teas are not. Juice, especially dark colored juices like mango and berry juices, are healthy in small (one glass a day) amounts. Coffee and tea, in moderation, are also sources of fluid. Research has shown that coffee does not cause dehydration.

How can I stop dry mouth without drinking water all day?

Some medicines and medical problems can cause annoying dry mouth. The best way to treat this is by increasing the amount of saliva you make. You can:

 Suck on a lozenge such as a sugar-free lemon drop

 Chew sugar-free gum

 Slowly nibble on a piece of slightly acidic dried fruit such as mango

 Try one of the many Biotene products that are made to relieve dry


Who does need to drink more water?

Your doctor may tell you to drink large amounts of water if you have certain medical problems such as kidney stones, a urinary tract infection or diarrhea.

What are signs of serious dehydration that needs treatment?

 Extreme thirst

 Extreme fussiness or sleepiness in infants and children; irritability and

confusion in adults

 Very dry mouth, skin and mucous membranes

 Little or no urination — any urine that is produced will be darker than


 Sunken eyes

 Shriveled and dry skin that lacks elasticity and doesn't "bounce back"

when pinched into a fold

Why do I keep hearing that I need to drink more to stay healthy?

Companies that make products such as bottled water sponsor and promote research that can be misleading. For example, a study that concluded that almost two-thirds of children in Los Angeles and New York City weren’t getting enough water was funded by Nestec, a subsidiary of Nestle Waters. But, the definition of dehydration they used is a value that has been found to be normal in healthy children for many years all over the world.

Some weight-loss programs tell you to drink 8 glasses of water per day to help you lose weight. While drinking a half liter of water right before you eat may fill the stomach so you become uncomfortable if you eat large portions, there is no evidence that high fluid intake leads to weight loss.


Where can I learn more?

Carroll, Aaron E. No, You Do Not Have to Drink 8 Glasses of Water a Day. New York Times, August 24, 2015.

Reference: Vreeman, Rachel C, and Aaron E Carroll. “Medical Myths.” BMJ : British Medical Journal 335.7633 (2007): 1288–1289. PMC. Web. 12 Nov. 2015.

Disclaimer: This document contains information and/or instructional materials developed by the University of Michigan Health System (UMHS) for the typical patient with your condition. It may include links to online content that was not created by UMHS and for which UMHS does not assume responsibility. It does not replace medical advice from your health care provider because your experience may differ from that of the typical patient. Talk to your health care provider if you have any questions about this document, your condition or your treatment plan.


Author: Diana Stetson, PA-C

Patient Education by University of Michigan Health System is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Last Revised 11/12/2015