How Much Water Should You Be Drinking?

How Much Water Is Enough?

mature woman drinking water
B2M Productions/The Image Bank/Getty Images

You may worry about drinking enough water to avoid dehydration and stay healthy depending on the season and the climate where you live. Eight glasses a day. That's what they say, right? Truth is, there's not that much scientific research about what exactly constitutes a healthy daily "dose" of water.

The prevalence of the eight-glasses-a-day doctrine is highlighted in a 2012 paper written by Spero Tsindos, a nutrition professor at La Trobe University in Australia.

Published in the Australian and New Zealand Journal of Public Health, the article presents some history on the origin of this advice, and some current context suggesting why the belief in a minimum water consumption rule remains so widespread.

According to Tsindos, back in the 19th century, alternative medicine practitioners called “hydrophathists” were among the first to advocate water - and lots of it - as a universal remedy. Vincent Priessnitz, from what is now part of the Czech Republic, is credited as the founder of hydropathy. His water “cure” prompted the establishment of water sanatoriums in the United States, Australia and Europe in the mid-1800s. Priessnitz and his supporters recommended drinking the equivalent of 1.1 to 1.7 liters of water per day.

More recently, according to Tsindos’ account, in the mid-1940s the National Academy of Sciences published a guide that links the required amount of water with the number of calories consumed in an average day: 1 milliliter of water for every calorie.

According to this calculation, a man who eats about 2,500 calories a day should drink about 2.5 liters of water a day.

The Dangers of Dehydration

Severe dehydration is dangerous. It can bring on seizures, brain damage and even death. Minor dehydration can aggravate conditions like constipation or urinary tract infections.

Even dental problems can arise from dehydration due to a lack of saliva in the mouth, which can be a problem for aging teeth. In otherwise healthy people, dehydration is most likely to occur after a bout of vomiting or diarrhea.

The Dangers of Over-Hydration

In the rare case a person consumes far too much water, hyponatremia can result. Hyponatremia is a serious condition in which the body’s electrolyte balance is thrown off, especially sodium. Dangerous brain swelling and death can result. While certain conditions like kidney disease and congestive heart failure can cause hyponatremia, it’s also been seen in marathon runners who over-consume fluids in advance of a big race.

How Much Water Is Enough?

Unlike many vitamins and minerals, there is no set minimum for daily water intake. According to the National Academy of Science Food and Nutrition Board, the “adequate intake” for water varies by age and gender. These numbers are derived from dietary survey data, so they are really a summary of how much people do consume, rather than how much they should consume.

The range is quite broad: for men aged 51-70, a daily consumption of about 1.9 liters total is indicated, including the water present in all foods and beverages. For women aged 51-70, the median consumption is about 2.0 liters per day from all sources.

A similar survey from Australia, cited by Tsindos, was conducted in 1995. It determined an optimal water intake from all sources to be 3.4 liters for men and 2.8 liters for women, though almost 40 percent of respondents failed to consume this much liquid.

In a 2008 editorial for the Journal of the American Society of Nephrology, University of Pennsylvania kidney specialists Dan Negoianu and Stanley Goldfarb also question the conventional 8-glasses-a-day wisdom. While they agree that people living in hot, dry climates and those exercising strenuously have an increased need for water, they cite a lack of any scientific evidence that eight daily glasses are necessary.

In addition, they point to conflicting studies regarding the benefits of greater water intake for any specific conditions, beyond kidney stones, and even then the evidence is only conclusive for people who have had a kidney stone already.

Water Intake and Weight Loss

Some research suggests that drinking more water will aid in weight loss, especially when the water replaces sugary beverages that would otherwise be consumed. Tsindos, Negoianu and Goldfarb dispute the weight loss claims, saying that no studies have proven that drinking a large volume of water throughout the day decreased caloric intake over the long-term.

What About Coffee and Tea?

Coffee and tea are made with water, so do they "count" towards your total water intake or do their diuretic properties mean you'll excrete more fluid that you took in? Tsindos addresses this notion, citing research that suggests the “diuretic effect of some beverages, such as tea or coffee, is somewhat overrated.”

The Bottom Line

Too little water and too much water each pose health hazards. While we consume fluids in the form of plain water each day, we also get water through foods like unprocessed fruits and vegetables, which contribute to the body’s level of hydration. In addition, Tsindos stresses, there is considerable evidence that water and a well-balanced diet do more for the body than water alone, a fact that often gets overlooked.

Finally, when it comes to how much water you should be drinking each day, let your body be your guide. You have a built-in hydration meter: your urine. If it’s dark yellow or orange in color, or if it has a distinctive or strong odor, you may be dehydrated, though certain medications can turn urine orange.

The usual color for healthy urine is light yellow, or straw-colored, and it should be clear enough that you could read a newspaper through it. Remember: your body will use water from any source, including healthy fruits and vegetables that are part of an anti-aging diet, and the coffee and tea that may also promote your longevity.

Sources:

Daniels MC, Popkin BM. “Impact of water intake on energy intake and weight status: a systematic review.” Nutr Rev. 2010 Sep;68(9):505-21.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2929932/?tool=pubmed

Dehydration. US National Institutes of Health Medline Public Information Sheet. Accessed June 25, 2012.
http://www.nlm.nih.gov/medlineplus/ency/article/000982.htm

Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate Panel on Dietary Reference Intakes for Electrolytes and Water, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. National Academies Press. 2005. Accessed June 25, 2012.
http://www.nap.edu/catalog.php?record_id=10925

Friedrich Manz, MD “Hydration and Disease.” J Am Coll Nutr October 2007 vol. 26 no. suppl 5.

http://www.tandfonline.com/doi/abs/10.1080/07315724.2007.10719655

Hyponatremia. US National Institutes of Health Public Information sheet. Accessed June 25, 2012.
http://www.nlm.nih.gov/medlineplus/ency/article/000394.htm

Margaret McCartney. “Waterlogged?” BMJ 2011;343:d4280.

Negoianu, Dan and Goldfarb, Stanley. “Just Add Water.” Journal of the American Society of Nephrology : JASN, ISSN 1046-6673, 06/2008, Volume 19, Issue 6, pp. 1041 – 1043.
http://jasn.asnjournals.org/content/19/6/1041.citation

Spero Tsindos. “What Drove Us to Drink 2 Litres of Water a Day?” Australian and New Zealand Journal of Public Health. Volume 36, Issue 3, pages 205–207, June 2012.
http://onlinelibrary.wiley.com/doi/10.1111/j.1753-6405.2012.00866.x/full

Continue Reading