How Much Water Do You Really Need for Good Health?

Monday Sep 16 | BY |
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Do you need to drink eight 8-ounce glasses of water a day? It depends on a number of factors.

The standard advice for years has been that you should drink eight 8-ounce glasses of water a day for optimal health. Is it true? What about some of the advice that more water is even better and may help with weight loss? Or that too much water can affect sleep or even cause kidney damage?

We did some research on both sides of the argument, and have reported what we found below. Did we come up with a definite answer as to whether more or less is best? No. In fact, a lot depends on health, where you live, how active you are, and a number of other factors.

Argument #1: More Water is Better

A recent study by the Centers for Disease Control and Prevention (CDC) found that forty-three percent of adults drink less than four cups of water a day. That’s nearly half of Americans that may not be getting enough water, though the CDC didn’t really qualify how much is “enough.”

(On the flip side, 35 percent drank four to seven cups a day, while 22 percent drank eight or more.)

Another interesting finding was that those who drank less than four cups a day were also those who ate the fewest fruits and vegetables, exercised the least, ate fast food more than once a week, and had the fewest family dinners. So it seems that those participants with healthier habits on the whole were the ones drinking more water.

Water provides a number of health benefits. It flushes toxins out of vital organs, carries nutrients to your cells, provides a moist environment for tissues, and much more. We can’t survive without water, and a lack of it can lead to dehydration and other health problems.

“Mentally and physically,” said Paula Burke, clinical dietician at MetroSouth Medical Center in Blue Island, “we’re better off being hydrated. The human body is about 70 percent water; we need it.”

When it comes to how much we need, however, the recommendations vary. Here are a few guidelines from different health organizations:

  • The Institute of Medicine says men need roughly 3 liters (about 13 cups) of “total beverages” a day, while women need 2.2 liters (about 9 cups).
  • The standard “eight 8-ounce glasses” recommendation gives you about 1.9 liters.
  • The 1989 Recommended Dietary Allowances stated that because requirements vary so much from person to person, establishing a recommendation that meets the needs of all is impossible.
  • The Dietary Reference Intakes established in 2004 recommend 3.7 liters a day for men, and 2.7 liters a day for women.

Drinking at least eight glasses a day, maybe a few more, has been linked with a number of health benefits. These include:

  • A recent study found that drinking water may boost mental performance. Those who drank about three cups of water before taking a battery of cognitive tests performed better on a test measuring reactive time than those who didn’t.
  • wo studies found that consumption of water increased thermogenesis—boosting the number of calories used by the body.
  • Adequate water intake prevents dehydration, which is associated with headaches, kidney stones, and impaired cognition.
  • Water intake before meals and as a replacement for sugar-sweetened beverages is associated with a lower energy intake and maintenance of a healthy weight.
  • The University of Maryland Medical Center recommends 6-8 glasses a day to possibly stave off osteoarthritis, and to decrease inflammation.
  • Water helps flush toxins out of the body, and at the right amounts, helps support the kidneys.
  • We need more research, but one small study suggested that increasing water intake helped reduce the intensity and duration of headaches.
  • Studies have indicated that low fluid intake is a prime cause of constipation.

Argument #2: Eight Glasses Aren’t Necessary—and Too Much Can be Harmful

Whereas there are a lot of proponents of increased water intake, you can drink too much water. It’s rare, but particularly during or after exercise, it’s possible.

Consuming too much water can result in a condition called “hyponatremia,” in which the body’s electrolyte balance is thrown off. Also called “water intoxication,” this condition taxes the kidneys, as they are unable to eliminate enough water from the system to maintain a safe level of electrolytes. As the circulatory system becomes diluted, electrolytes drop, and water seeps into the cells, causing cells to swell. Dangerous brain swelling, seizures, and death can result.

This is rare, however, and occurs in extreme situations, such as during marathons or other athletic events, when athletes are exercising longer and drinking more than usual. To avoid it, don’t force yourself to drink more than you’re thirsting for, and drink sports drinks during prolonged exercise, which have a smaller diluting effect on the blood.

Other than this condition, however, there are few drawbacks to drinking more water. Some recent studies, however, have indicated that the eight-glasses-a-day rule may be a myth. A 2008 study, for instance, reported that most people do not need to worry about drinking 8 glasses a day, as there is no clear evidence that increasing water intake provides any health benefits. On the other hand, they went on to note that neither is there any clear evidence that drinking more does not benefit health.

Instead, they concluded that there is just a general lack of evidence about how much water humans need.

How to Decide

According to the Mayo Clinic, there are a number of factors that influence how much water you need. These include:

  • Exercise—how active you are determines how much fluid you lose and how much you need to replace.
  • Weather—hot or humid weather, heated indoor air, and high altitudes require additional water intake.
  • Fever, vomiting and diarrhea all drain moisture from the body, requiring more intake to rebalance hydration.
  • Pregnant and breast-feeding women need additional water to stay hydrated.

To decide how much you need, listen to your body. Many health experts recommend watching the color of your urine—dark orange or yellow or with a strong odor means possible mild hydration. Go for a light yellow or straw-colored shade.

Some people have heard that by the time they feel thirsty, they’re already dehydrated, but actually, your thirst is a good indicator most of the time—as long as your listening to your body and are not absorbed in other things that cause you to ignore it.

Also, take into account the fluids you get from other beverages and from food. These do count toward your total fluid intake for the day.

Bottom Line: If you drink enough so that you rarely feel thirsty, and your urine is colorless or light yellow, you’re probably getting enough. If you find yourself dragging throughout the day, try drinking another glass or two.

How much water do you drink every day? Do you find that more is better?

* * *

A. Grandjean, “Rolling Revision of the WHO Guidelines for Drinking-Water Quality,” WHO,

“Drinking water may boost mental performance: study,” NY Daily News, July 17, 2013,

Leslie Mann, “Study finds nearly half of Americans not drinking enough water,” Chicago Truibune, June 5, 2013,

Dr. Stanley Goldfarb, “Just Add Water,” JASN, June 2008, 19(6):1041-1043,

Boschmann M, Steiniger J, Hille U, Tank J, Adams F, Sharma AM, Klaus S, Luft FC, Jordan J: Water-induced thermogenesis. J Clin Endocrinol Metab 88 : 6015 –6019, 2003.

Boschmann M, Steiniger J, Franke G, Birkenfeld AL, Luft FC, Jordan J: Water drinking induces thermogenesis through osmosensitive mechanisms. J Clin Endocrinol Metab 92 : 3334 –3337, 2007.

Alyson B. Goodman, et al., “Behaviors and Attitudes Assocaited with Low Drinking Water Intake Among US Adults, Food Attitudes and Behaviors Survey, 2007,” Prev Chronic Dis, 2013;10:120248,

“Osteoarthritis,” University of Maryland Medical Center,

Jhandler, “Benefits of drinking water,” Mother Nature Network, November 16, 2011,

M. G. Spigt, et al., “Increasing the daily water intake for the prophylactic treatment of headache: a pilot trial,” European Journal of Neurology, September 2005, 12(9):715-718,

M J Arnaud, “Mild dehydration: a risk factor of constipation?” European Journal of Clinical Nutrition, 2003, 57(ss 2): S88-S95,

“Evidence lacking on health benefits of drinking lots of water,” American Society of Nephrology, Press Release, April 2, 2008,

Colleen M. Story

Colleen M. Story

Colleen M. Story, a northwest-based writer, editor, and ghostwriter, has been creating non-fiction materials for individuals, corporations, and commercial magazines for over 17 years. She specializes in the health and wellness field, where she writes and ghostwrites books, e-books, blogs, magazine articles, and more.

Colleen is the founder of Writing and Wellness. Her fantasy novel, “Rise of the Sidenah,” was released with Jupiter Gardens Press in September 2015. Her literary novel, “Loreena’s Gift,” is forthcoming in spring 2016 from Dzanc Books. She lives in Idaho.


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  1. Great article. I always felt that drinking the prescribed amount of water was always a struggle in the beginning. It’s a great cleanser and will actually make you feel “fresh” once you begin to get used to drinking a lot of water each day.

  2. Dave says:

    I agree, it’s tough to begin with because you feel like you constantly need to go to the toilet but drinking more water definitely helps you feel more awake and alert plus I find it keeps your appetite at bay for slightly longer which helps discourage you from snacking. I usually drink about 1.5L but I’m sat at a computer desk not doing much exercise. When I’m not working I’m easily drinking 2, maybe 2.5L daily.

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