It’s pretty easy to hoax people. We all want to be deceived, but only up to a point. Some hoaxes are fun and pleasant, others malicious and unpleasant. We’d like a way to tell the difference (Robert Carroll).

Sep 11, 2011

Drinking 8 Glasses of Water Daily: Good or Bad for your Health?

Surely, you have read the statement multiple times in the health-related posts online and offline, that drinking 8 glasses of water every single day is essential for keeping your health in the good shape. To make sure you got the message, your friends definitely forwarded you the scary messages that if you will not follow the rule, you will get thick soon from multiple disorders.  The rule is usually referred as "8 x 8", since each one out of 8 glasses you drink, should be 8-ounces, making it 64 ounces of total daily consumption. The only positive side in those messages is that you are not alone who underdrink –it is claimed that 75 percent of Americans are chronically dehydrated and fail to drink the specified amount of water per day recommended by health and nutrition experts.

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I do not think you ever followed the "8 x 8" rule every time you read about that. Most likely, you felt guilty of not doing of what is advised, but you continued your regular nutrition and hydration routine. But if you try to follow it religiously, you might spend a lot of time running to the bathroom, and you might not see substantial improvements to your health.


Why do so many people believe this rule? Why do so many doctors and writers and bloggers on the health related topics still include it in the list of the advisable actions?

The number originally came from the National Academy of Sciences of the United States Food and Nutrition Board, which publishes recommended daily allowances of nutrients. The 1945 edition of the Food and Nutrition Board recommended: "A suitable allowance of water for adults is 2.5 liters (about 8 cups) daily in most instances." This amount is based on the calculation of one milliliter of water for each calorie of food. HOWEVER, the Board also noted that most of the water you need is in the food you eat.

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The Board revisited the question of water consumption in 2004. Its panel on "dietary preference intakes for electrolytes and water" noted that women who appear adequately hydrated consume about 91 ounces (2.7 liters) of water a day and men about 125 ounces (3.7 liters). These seemingly large quantities come from a variety of sources—including coffee, tea, milk, soda, juice, fruits, vegetables and other foods. Instead of recommending how much extra water a person should drink to maintain health, the panel simply concluded that "the vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide."

Why the medical misconception, originated in 40s, is still flourishing in our well-informed and well-educated environment? Because somebody benefits from that! One of the most probable reasons of why this “8 X 8” myth is alive and doing well can be traced to aggressive marketing tactics by the bottled water industry, including the Hydration for Health initiative, which is sponsored by the French food giant Danone, maker of Volvic, Evian and Badoit bottled waters.

Scientific Background

All foods contain water. Even the driest nut or seed has a lot of water in it. Furthermore, when food is digested, it is converted to energy, carbon dioxide and WATER. Most people can get the fluid the body needs from food, and they only need to drink enough water to prevent constipation.

When you eat, the pyloric valve at the end of your stomach closes to keep food in the stomach. Then the stomach takes fluid that you drink and food that you eat and turns the solid food into liquid. If you don't drink enough fluid, your stomach takes fluid from your blood and adds it to the food in the stomach to create the soup. The pyloric valve will not let food pass to the intestines until this liquid soup is formed. Then the liquid soup passes to the intestines and remains a soup until it reaches your colon. Only then is the fluid absorbed to turn the soup into solid waste in the colon. If you do not have enough fluid in your body, your body extracts extra fluid from your stool and turns your stool into hard rocks, causing constipation.


A study in the Journal of the American College of Nutrition shows that plain water is not needed as long as enough fluid is obtained from other drinks and food. Twenty-seven healthy men consumed one of two diets for three-day periods and were studied in a lab setting. The first diet included plain water while the second omitted it, relying on only foods, orange juice, diet soda, and coffee for fluid. None of the nine measures of hydration were affected.

Heinz Valtin, MD, professor emeritus of physiology at Dartmouth Medical School, published results of his study on the topic in American Journal of Physiology, confirming the "8 x 8" rule is not supported by the scientific evidence.

He noted that surveys of fluid intake on healthy adults of both genders, published as peer-reviewed documents, strongly suggest that such large amounts are not needed. His conclusion is supported by published studies showing that caffeinated drinks, such as most coffee, tea and soft drinks, may indeed be counted toward the daily total. He also pointed to the large body of published experiments that attest to the capability of the human body for maintaining proper water balance.

Valtin emphasized that his conclusion is limited to healthy adults in a temperate climate leading a largely sedentary existence - precisely, he pointed out, the population and conditions that the "at least" in "8 x 8" refers to. At the same time, he stressed that large intakes of fluid, equal to and greater than 8 x 8, are advisable for the treatment or prevention of some diseases, such as kidney stones, as well as under special circumstances, such as strenuous physical activity, long airplane flights or hot weather. But barring those exceptions, he concluded that we are currently drinking enough and possibly even more than enough.

That is true, Valtin goes further in his assessment, claiming that drinking too much water can bring harm to your health. "The fact is that, potentially, there is harm even in water," explains Valtin. Even modest increases in fluid intake can result in "water intoxication" if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes, in teenagers after ingesting the drug Ecstasy, and in ordinary patients.

And he lists other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8. Other claims discredited by scientific evidence that Valtin discusses include:
  • Thirst Is Too Late. It is often stated that by the time people are thirsty, they are already dehydrated. On the contrary, thirst begins when the concentration of blood (an accurate indicator of our state of hydration) has risen by less than two percent, whereas most experts would define dehydration as beginning when that concentration has risen by at least five percent.
  • Dark Urine Means Dehydration. At normal urinary volume and color, the concentration of the blood is within the normal range and nowhere near the values that are seen in meaningful dehydration. Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances.

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In 2008 Dan Negoianu and Stanley Goldfarb reviewed the evidence for the Journal of the American Society of Nephrology. They came to a similar conclusion: "There is no clear evidence of benefit from drinking increased amounts of water."

One of the statement, advocating the 8 x 8 guideline claims that thirst is a poor hydration indicator, since many people are so chronically dehydrated they no longer recognize their bodies' signals for water. Barbara Rolls, professor of nutrition sciences at the Pennsylvania State University, disagrees. Her studies, she says, "found no evidence that people are chronically dehydrated." She also contradicts to the popular belief that people mistake thirst for hunger, which causes them to eat when they are really just thirsty, arguing that "drinking water and waiting for pounds to melt away does not work. We all wish it were that simple." She explains that "hunger and thirst are controlled by separate systems in the body. People are unlikely to mistake thirst for hunger." Furthermore, she reports that her studies "never found that drinking water with or before a meal affected appetite." Nevertheless, there are some elements of truth in the misperception. Rolls did find that water-rich foods—as opposed to stand-alone water—tended to help people consume fewer calories. And, she says, "there is a way that water can help with weight loss—if you use water as a substitute for a caloric beverage."

And the most recent 2011 move to debunk the myth was made by the Scottish practitioner Margaret McCartney in the current issue of the British Medical Journal. McCartney took on medical claims disseminated by Hydration for Health, a water-pushing health organization created by the company that owns Volvic and Evian. McCartney wrote that she did not see any high-quality scientific literature provided by Hydration for Health proving drinking so much water was essential. In fact, she found evidence that mental performance suffers when people drink more water than they're thirsty for. "In other words, there is still no evidence that we need to drink more than we naturally want, and there may be unintended harms from an enforcement to drink more water," McCartney wrote.

While McCartney didn't see evidence backing up the 2-liter-a-day rule, she did see bottled water companies pushing the "water=health" idea to sell more of their products. So, indeed, somewhere at the bottom of this cleverly organized hoax is somebody profit, as was already suggested above. As McCartney wrote on her blog: "The bottled water industry is pushing the idea that we should drink more than we normally would with the promise of health benefits, and I don’t think there are any". The bottled water companies were not happy with McCartney's attitude. In response, the European Federation of Bottled Waters wrote a letter to BMJ about McCartney's article and cited a recommendation that "at least two liters of water should be consumed per day."

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A reasonable amount for a healthy human is one cup of water or any other fluid with each meal. If you have a problem with constipation you may not be drinking enough water, but if you are not constipated, you are getting plenty. You'll also want to replace fluids whenever you sweat a lot, particularly when you exercise or in hot weather. Drink water whenever you feel thirsty, but there's no health benefit from forcing yourself to drink eight glasses of water a day. Drinking too much water can be dangerous. This is of particular concern if you are exercising in hot weather and fail to replace the salt you lose in sweat.

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