It may be one of the oldest beliefs, ascribed by both medical practitioners and lay press for hundreds of years: "The average person should drink at least 8 glasses of water a day for optimal wellness."

But how many people know that the roots of this adage aren’t in science, but vitalism and nostrum remediums? How many know that after centuries, there’s still no medical evidence for the belief that normal, healthy people all need to be concerned about drinking more water?**

The lack of evidence shouldn’t really be a surprise if we stop to think about it. As Dr. Heinz Valtin, M.D., a kidney expert with the Department of Physiology at Dartmouth Medical School in New Hampshire, said, it’s “difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake.”

Yet, we only need to look around to see how slavishly this exhortation is being followed. People carry bottles of water everywhere, sipping from them continually. We’ve become obsessed with our pee. More incredibly, so have our employers.



Pee charts

Companies have made workers’ bathroom business their business. Drinking 8 (8 ounce) glasses of water — known as 8x8 — has become a key part of preventive health and workplace wellness programs. Like many other aspects of these wellness programs, their claims to prevent chronic diseases and promote optimum wellness have little credible scientific support.

It shouldn’t be at all surprising that our bosses don’t know what’s best for us, though. How many human resource departments and company executives do you know who read the medical literature and understand science? So why are we readily accepting health advice at work? In fact, the off-the-wall claims being made by those that sold wellness programs to our bosses may be most surprising of all.



They’re told that hydration is essential to a healthy workforce. A recent Personnel Today magazine article, for instance, said that even the slightest dehydration affects job performance. Dehydration drains energy and reduces productivity, affecting companies’ bottom line, executives are told. Vielife, which provides employer wellness programs, claims “a 1% decrease in hydration levels produces a 20% decrease in production levels.”

As part of Vielife’s hydration program, for example, to ensure that employees are drinking enough water, companies offer water points, send emails to coax workers to drink water, distribute water bottles, and post pee charts in the bathrooms to check the color of workers’ urine. Yes, pee charts. Bosses actually think it’s their business what you do in the privacy of the bathroom. Don’t laugh, Vielife’s Hydration Campaign and wellness programs have been adopted by companies around the world, such as Australia’s largest health plan, Medibank Private, which covers 90,000 employees; and Tameside Metropolitan Borough Council, which covers 4,600 employees in East Manchester.

Unsupportable claims about water abound in the tenuous health information being given people through wellness programs. Mayo Clinic, which provides the online health information through many employer and healthplan wellness program, says water flushes toxins out of vital organs and that even mild dehydration can drain energy and make you feel fatigued. To stay “safely hydrated,” Mayo Clinic advises: “It's generally not a good idea to use thirst alone as a guide for when to drink. By the time you become thirsty, it's possible to already be slightly dehydrated.”

At the University of Maine, during campus Healthy Weight Week, employees were told by their wellness director:

DRINK WATER! Most of us suffer from mild dehydration, and it’s important to focus on drinking water all day, every day. Try to consume about ten 8-ounce glasses of water every day (about 5 bottles of water), and remember that caffeine is dehydrating—if you drink a lot of coffee or caffeinated soda, you’ll need to drink more than ten servings of water a day. If you’re tired, hungry, cranky, light-headed— you may just need a glass of water. So run to the faucet or the nearest gas station and start hydrating!

These beliefs about water have certainly helped the bottled and purified water industries — among of the biggest promoters of the 8x8 adage and the water wellness factor for workplace wellness. But, clearly, we need better sources of information, lest we be taken in, too.

For years, the recommendation to drink 8 glasses of water a day for good health had become one of those unquestioned rules that was so widespread, most people assumed there must be some scientific medical basis for it. On the contrary. In fact, most of us would probably be astounded to learn that it dates back to early philosophies — vitalism ideologies.



Living water

Water for health is an idea that goes back centuries, at least. German physician, Christoph Wilhelm Hufeland (1764-1836), who practiced natural medicine and vitalism, fashionable at the time, was one early proponent of 8-10 glasses of water a day. He is most known for founding macrobiotics, and his book, Makrobiotik oder Die Kunst, des Menschliche Leben zu verlangern, attributed health and ill health to life force. According to the Dictionary of Eighteenth Century German Philosophers, he sought “not just a longer and healthier life, but also a more ethical life — moral and physical health were seen as intertwined and flowing from the same source, both marked by an abundance of life force. Illness was not to be cured so much as prevented by pursuing a proper diet and lifestyle.”

In Hufeland’s Art of Prolonging Life, translated in 1867, he wrote:

The first thing necessary in regard to the prolongation of life must undoubtedly be a more intimate acquaintance with...the vital power, the grand cause of all life... The vital power is the most subtle, the most penetrating, and the most invisible agent of Nature...it exceeds light, electricity, and magnetism. The vital power may be weakened, and even totally destroyed, by certain causes; and by other can be excited, strengthened and nourished... Water, if it be not nourishment of itself, it at any rate indispensably necessary for the business of restoration and nourishment; first, because it must be the vehicle for the proper nutritive substances... and secondly, because this vehicle is absolutely necessary to produce sufficient secretion and evacuation of what is corrupted, and consequently for the purification of the body.

In Makrobiotik, he said water, preferably alive, fresh spring or mineral water, was the best drink and “an excellent means of prolonging life.” But, he added, “the most essential thing is that it should be fresh; for in its freshness there is a certain sprit, which in a peculiar manner renders it so digestive and fortifying.” Many special curative properties were attributed to fresh, cold water, which he said was a “fortifier and vivifier of the stomach and nerves, and an excellent antibilious and antiputrid remedy.”

In Makrobiotik, Dr. Hufeland described his water prescription to drink at least 8 glasses of water a day. He advised drinking 2 or 3 tumblers of cold spring water upon rising, drinking more cold water to diminish the exciting effects of coffee or tea after breakfast, a tumbler of water an hour before dinner, 3-5 glasses during dinner, and a glass of water before going to bed. Water was necessary, he wrote, “above all in youth, when the blood begins to boil in the veins, that is particular necessary to have recourse to cold water to calm the natural effervescence of the blood. In manhood, which naturally disposes us to febrile and inflammatory diseases and old age...there is no better way of preventing and remedying these evils, than to drink cold water.”

While his book was written in 1796, this water adage appears to have been being promoted even prior to that date. Dr. Hufeland described the Surgeon General to the King of Prussia, who, from the age of 30, had suffered from “hypochondria, melancholy, heart palpitations, and indigestion.” By following his water diet, “all his complaints disappeared” and he was said to have enjoyed better health the last half of his life than he had during his youth.

Throughout the 18th and 20th centuries, the hydropathy water cure was popular in Europe and America, as practitioners encouraged their followers to drink lots of water for healthful and curative properties and to flush out toxins and impurities. Dr. Granichstadten, a follower of hydropathy, wrote in Hydriasiologie, in 1837, that cold water followers will “find his appetite, which he may indulge as much as he likes, and his gaiety increase daily, and his pains and aches diminish; and when he becomes acquainted with the nature of the cure, he will feel a confident assurance of being speedily established in health.”

By 1840, there were just under 100 different hydropathy medical centers in Germany, alone, wrote Captain R.T. Claridge in Hydropathy: The Cold Water Cure, published in 1845. Throughout the early 1900s, the media continued to regularly espouse drinking 8 glasses of water a day.

The 8x8 recommendation continued, rarely questioned, until Dr. Valtin’s seminal investigation in 2002, trying to find any scientific justification for drinking so much water. This was followed by other critical papers and the 2004 National Academy of Sciences recommendations. Still, the scientific evidence hasn’t caught up with some health writers, nutritionists and healthcare professionals. Nor, obviously, with our employers.



The science of 8x8

Conventional wisdoms, despite their popularity, aren’t always true. Dr. Valtin conducted a 10-month review of the scientific literature and historic documents, and interviewed medical experts, to find any supportive evidence at all for this long-standing adage. He also looked for any evidence behind the most cited claims about the our water needs and water’s health benefits. “I’m talking about randomized trials published in peer-reviewed journals,” he said. Not opinion pieces and anecdotes. He also tried to uncover a definitive science-based origin for the recommendation.

His major undertaking found that “the universal advice that has made guzzling water a national pastime is more urban myth than medical dogma and appears to lack scientific proof.” His search results, published in the American Journal of Physiology, said:

No scientific studies were found in support of 8 x 8. Rather, surveys of food and fluid intake on thousands of adults of both genders — analyses of which have been published in peer-reviewed journals — strongly suggest that such large amounts are not needed because the surveyed persons were presumably healthy and certainly not overtly ill. This conclusion is supported by published studies showing that caffeinated drinks (and, to a lesser extent, mild alcoholic beverages like beer) may indeed be counted toward the daily total, as well as by the large body of published experiments that attest to the precision and effectiveness of the osmoregulatory system for maintaining water balance.

His review of lay press found that the rationale for 8x8 typically goes something like this: “Our bodies consist mostly of water and our blood, muscles, brain, and bone are made up mainly of water. Therefore, 1) we need water to function and survive and 2) we need at least eight 8-ounce glasses of water each day.” The second conclusion, he said, besides being unproven is a nonsequitur. “It is akin to arguing that our homes run on electricity, and that, therefore, every house needs at least 1,000-ampere service.”

Dr. Valtin specifically investigated the research evidence behind the most popular myths about our fluid needs.

All fluids count. The popular papers left “little doubt” that most advocates of the 8 glasses of water a day mean to convey that people should drink water per se, and specifically exclude caffeinated or sweetened drinks from the daily count. But this is a misperception, he wrote. He found strong scientific evidence that all fluids count, including water, coffee, tea, soft drinks, milk, juices and beer .

Dehydrating caffeine myth. Similarly, he found that recent experiments have “cast serious doubt on the often asserted diuretic role of caffeinated drinks,” he said. Caffeine had no significant effects on any of the variables that measure dehydration in one such study conducted at the Center for Human Nutrition in Omaha, for example, and the investigators concluded that “advising people to disregard caffeinated beverages as part of the daily fluid intake is not substantiated.” The diuretic effect of caffeine in drinks and moderate alcohol is trivial compared to the amount of water they contain.

We need less than we think. Among most adults, he found, caffeinated and alcoholic beverages constitute half or slightly more of their daily fluid intake, meaning the average adult drinks a respectable 1,700 ml and this doesn’t include the water from foods and metabolism, which also count . Yet, the medical research indicates that even 1,700 ml may be as much as a full liter more than what sedentary adults actually need to maintain physiological homeostasis, he said.

He couldn’t find any article where 8x8 was recommended on the basis of scientific evidence. The idea seemed to appear out of nowhere. He did, however, find one possible source for a misinterpretation that may have been repeated, like urban legends often are. The 1945 Food and Nutrition Board of the National Academy of Sciences had written in its Recommended Dietary Allowances:

A suitable allowance of water for adults is 2.5 liters daily in most instances. An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods.

Dr. Valtin believes this last sentence may have been ignored, leaving the incorrect interpretation of these early dietary guidelines that eight glasses of water to be drunk each day.

Thirst doesn’t mean dehydration. The scientific evidence also debunks the popular myth that by the time you feel thirsty, you’re already dehydrated. A number of scientific studies have confirmed there is no support for this fear. Quite the opposite. Thirst hits long before we're near risk for dehydration. Our thirst kicks in when the osmolality of our blood plasma is less than 2%, whereas dehydration begins at osmolalities of 5% and higher. In fact, our bodies even adjust fluid balances moment-to-moment by changes in the plasma concentrations of the antidiuretic hormone vasopressin, and subsequent changes in urine flow, far earlier than thirst plays a role. “Osmotic regulation of vasopressin secretion and thirst is so sensitive, quick, and accurate that it is hard to imagine that evolutionary development left us with a chronic water deficit that has to be compensated by forcing fluid intake,” he wrote.

In the absence of diseases or other impairment of the osmoregulatory system, the body easily maintains water balance by this finely tuned system. It also can slow down evaporation through the skin and signal the kidneys to release water back into the body when needed. “The body’s own system is quick to restore water balance in healthy persons,” he said.

Pee color. While urine volume varies among healthy people, he said, there is a range of normal urine osmolalities among healthy people. The mean osmolality has a concentration of solutes so that the urine appears moderately yellow in color, he said, “which might be interpreted as ‘dark’, especially when contrasted against ‘pale yellow’ or ‘clear,’ which is specified in most of the lay literature.” But osmolalities in normal range are nowhere near the values of 300 mosmol/kgH2O and higher, which are seen in meaningful dehydration. “Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances,” he said.

Even water isn’t harmless. “Despite the dearth of compelling evidence for 8x8,” he wrote, “many persons are likely to retort: ‘But what harm would it do?’ The fact is that, potentially, there is harm even in water.” For example, he noted water intoxication and hyponatremia, covered here.

And then there’s the hassle, he said. Although some may dismiss this as minor, it can be a major inconvenience that can even cause embarrassment for some, he said. And those who’ve come to believe pure water is needed from bottled or purified sources, they can incur fairly large financial costs.

When the managing director of Vielife was asked about the downside of their employee hydration program and the inefficiency of having workers visiting the toilet all the time, he told Australian businessmen: “Well, I do all my best thinking in the toilet.” Employers bought that one, too. :-)

We are not a dehydrated populace . Examining multiple dietary surveys, he found that average daily water intakes during the 1990s were about 2,220 ml, far beyond that necessary for physiological homeostasis. Yet “proponents of 8x8 continue to tell us that ‘Americans still do not drink enough water,’” he wrote. The published data to date strongly suggest that “we probably are currently drinking enough and possibly more than enough.” [Again, some disease states and special circumstances such as strenuous physical activity and hot environments can increase our water needs, said Dr. Valtin, but that’s not who’s targeted by 8x8 recommendations.]

I would argue further that, for the time being, the burden of proof that everyone needs 8x8 should fall on those who persist in advocating the high fluid intake without, apparently, citing any scientific support.



2004 Food and Nutrition Board

Two years after Dr. Valtrin’s famous paper, the latest 2004 Food and Nutrition Board recommendations for water were issued, reinforcing his findings and defusing the myths of 8x8.

The Board clearly stated that total water intake includes fluids from drinking water, water in other beverages, and the water in food. They found the evidence insufficient to establish intake recommendations to reduce the risk of chronic diseases but has set Adequate Intake for total water to prevent health problems from dehydration. As they emphasized: “A wide variety of intakes is compatible with normal hydration... and Adequate Intake should not be interpreted as a specific requirement.” Daily consumption below the AI may not raise health risks for the typical person.

Higher total water is needed by people who are active or exposed to hot environments.

Over the course of a few hours, body water deficits can occur due to reduced intake or increased water losses from physical activity and environmental (e.g., heat) exposure. However, on a day-to-day basis, fluid intake, driven by the combination of thirst and the consumption of beverages at meals, allows maintenance of hydration status and total body water at normal levels.



The latest debunking

In the June issue of the Journal of the American Society of Nephrology, doctors Dan Negoianu and Stanley Goldfarb at the Renal, Electrolye and Hypertension Division at the University of Pennsylvania, further examined the science behind water myths. “There is what I call an urban myth that drinking a lot of water is a healthy thing to do and it leads to people toting around plastic water bottles all day drinking water,” said Dr. Goldfarb. “The source of this is the complementary and alternative medicine worlds.” Not science.

Water doesn’t reduce appetite. Among the additional myths they reviewed was the belief that drinking water before and during a meal will help people eat less and help manage obesity. They found surprisingly little evidence to support such rationale or even biological plausibility. “Because you absorb water so quickly and it moves through the GI tract so quickly, it probably doesn't fill you up the way people have proposed, nor does it lead to the release of hormones which suppress appetite,” he said.

Water doesn’t detoxify. Another myth is that filling up on water flushes toxins from the body. “In fact, that is not how the kidney works,” said Dr. Goldfarb. “When you drink a lot of water you end up having a larger volume of urine but don't necessarily increase the excretion of various constituents of the urine.”

Urban myth. While they did find solid evidence that some athletes or those living and working hot, dry climates have increased need for fluids; and that people with certain diseases may benefit from increased water intake; no such data exist for average, healthy individuals. As they summarized:

There is no clear evidence of benefit from drinking increased amounts of water. Although we wish we could demolish all of the [other] urban myths found on the Internet regarding the benefits of supplemental water ingestion, we concede there is also no clear evidence of lack of benefit. In fact, there is simply a lack of evidence in general.



Our bodies are amazing creations. There is no credible scientific reason that the average healthy person can’t trust his/her body to do what it was designed to do, and without continual diligence on his/her part. Counting and tracking everything that goes in and out — including calories, grams of macro- and micro-nutrients, and water — doesn’t make us any healthier. But it sure adds to our stress and makes us feel guilty when we stray outside the lines.





© 2008 Sandy Szwarc