“You need to drink at least eight glasses of water a day.” This old standard has been preached by almost everyone — doctors, dietitians, athletic trainers, health columnists, and massage therapists, to name a few. Most likely, you have offered this same advice or something similar. This largely unchallenged message can be found repeatedly in all types of media, including massage literature.

As a student of therapeutic massage at the Community College of Rhode Island, I was not surprised to find this message had taken a steadfast hold on the massage community. Most recently, I found it in a massage-related article.¹ The author, Joy Bicknell, says a diet containing lots of fruits and vegetables will supply the body with about four cups of water per day. But, in addition to this, she writes it is still necessary to drink another 6–8 cups of water per day. And, for every beverage you drink containing caffeine or alcohol, she advises consuming an additional glass of pure water (some recommendations call for just an additional half glass). Lastly, the author (like so many before her) says if you choose to listen to your own internal signals and wait to drink until your body tells you you’re thirsty, you are already dehydrated.

A simple look at these statements brings forth a multitude of questions: From where, and when, did this advice to push fluids into our bodies appear? Where did the standard 6–8 glasses of water per day (excluding caffeine and alcoholic beverages and ignoring your innate signal of thirst) come from? Surely, this practice has not always been so widely encouraged? Did its originators derive these recommendations from scientific fact? Is it possible that all people within our society really need to drink at least eight glasses of water a day indiscriminately? Are there people who may actually be at risk from drinking this much water? Can the diuretic effect in one alcoholic or caffeinated beverage really cause your body to lose an amount of fluid equal to what you just drank? Is it possible that massage therapists, whose ultimate goal is to support the well-being of their clients, may actually be offering them unproven advice when they say “drink more water”?

As a registered nurse experienced in the field of urological research, I have been a frequent witness to the adverse results people can create for themselves when attempting to satisfy this recommendation of eight, 8-ounce glasses of water (8 x 8) per day. And how many of us have felt guilty by not meeting that requirement? But the tide is changing. The Strength and Conditioning Journal reports that this recommendation, “is a blend of fashion and fiction and very little science,”² and other journals are asking if this recommendation is excessive for the average, healthy adult.

Over-Hydration a Problem

Over the course of my urological nursing career, I have worked extensively with patients experiencing all types of bladder dysfunctions, including benign prostatic hyperplasia (enlarged prostate), stress and urge urinary incontinence, and overactive bladder. These patients describe many similar symptoms, including difficulty urinating, frequent urination, waking frequently at night to urinate, and sometimes even the sudden, uncontrolled loss of urine.

These symptoms may have a noticeable effect on the patient’s quality of life. Waking at night to urinate causes loss of sleep, possibly resulting in decreased work productivity during the daytime. Frequent urination can cause significant embarrassment and limit a person’s activity because he or she fears being away from a convenient bathroom. Urinary incontinence can also cause both embarrassment and fear of smelling like urine. These problems can decrease a person’s desire to socialize and may also contribute to depression.

A high fluid intake not only exacerbates the severity of symptoms associated with a problematic bladder, but it can actually intensify the problem. As part of patients’ initial urological exams, I have always asked how much fluid they drink per day. The majority report an excessive fluid intake. When questioned about the rationale for this behavior, each of them points to the 8 x 8 recommendation. This advice has been so reinforced into their behavior pattern that they continue to push fluids, despite the fact they are frequently rushing to the bathroom, losing sleep from waking at night to urinate, and even urinating uncontrollably.

Many of these patients will come to their appointment toting a large bottle of water or a supersized soft drink and simultaneously ask why they are uncontrollably running to use the bathroom. In many cases, we find the cause for these symptoms is that indeed the patient has a bladder problem, combined with excessive fluid intake. It is often possible to decrease the severity of their symptoms simply by advising them to reduce their fluids. For some of these patients, it’s also not unusual to find no bladder disorder exists; the patient is merely pushing excessive amounts of fluid as they try to satisfy the eight glasses of water per day recommendation. Time after time, the simple instruction to reduce their daily intake of fluids alleviates, or ends completely, these patients’ problems.

As Jacques Susset, M.D., professor emeritus of urology at Brown University Medical School, explains, an excessive intake of fluids combined with delayed urination can negatively impact the normal contraction of the bladder.³ As the bladder fills, the bladder wall becomes thinner as it is stretched, just like the wall of a balloon as it fills with air. Over time, excessive fluid intake and delayed urination cause capillary stretching within the bladder muscle, resulting in a decreased blood supply to the bladder wall and loss of bladder muscle. Eventually, this will produce a replacement of the bladder’s smooth muscle cells with collagen. If these behaviors continue, Susset points out, significant build-up of collagen in the bladder wall may lead to an irreversible bladder dysfunction. In extreme cases, a severely dysfunctional bladder may allow the reflux of urine back into the kidneys, potentially compromising kidney function.

Some professions, he suggests, may be at an increased risk of developing a problematic bladder condition due to the inconvenience of stopping to use the bathroom when it’s necessary. Wait staff, truck and taxi drivers, and nurses are some professions he says may be at risk. This type of behavior also describes the profession of massage therapy. Long hours devoted solely to the care of clients, combined with the inconvenience of interrupting a session to use the bathroom and short turnover times between clients, contribute to delayed urination. Combine that with the standard 8 x 8 water recommendations and you could have a problem.

How Much is Too Much?

Unfortunately, trying to review the scientific literature available to support the 8 x 8 per day recommendation is not possible. According to Heinz Valtin, M.D., professor emeritus at Dartmouth Medical School, there is no past or present scientific evidence supporting the consumption of drinking at least eight glasses of water per day for the average, healthy adult.⁴ Valtin recently released his results in the American Journal of Physiology after an exhaustive and detailed search he made in an attempt to find evidence supporting this highly prevalent recommendation. He reports that after performing a comprehensive review of multiple electronic databases, interviewing several nutritionalists specializing in the field of thirst, and dialoguing with many water balance specialists, he has been unable to produce any evidence in support of consuming at least eight glasses of water per day. In fact, he reports that the majority of available literature reviewed says drinking at least eight glasses of fluid per day for the average, healthy, sedentary-
to-mildly-active adult is not necessary.

The Strength and Conditioning Journal supports Valtin’s claims by reporting that kidney physiologists at the National Institutes of Health believe an average-sized, sedentary adult in a temperate climate requires about four, 8-ounce servings of fluid a day to replace fluid losses.⁵ This amount is roughly what is obtained through daily food intake. Says the article’s author, “In short, though doctors do not recommend it, many of us could cover our bare–minimum daily water needs without drinking anything during the day.”

A Myth is Born

But how is it that something considered such common knowledge and prescribed by so many could largely be a falsehood? Although the true roots for the derivation of this statement are unknown, Valtin says a likely origin of this advice appears to have been born from a misinterpreted report published by the Food and Nutrition Board of the National Research Council. In 1945, the Food and Nutrition Board reported that a suitable fluid intake of water for adults was 2.5 liters per day (84.5 fluid ounces) or 1 milliliter of water for each calorie of food consumed. The original publication also reported that most of this quantity of fluid is contained, and can be obtained, within the foods we consume. Unfortunately, it would appear this latter piece of information seems to have been lost in the publication’s translation, leaving us with this advocacy to consume eight glasses of water per day, in addition to the fluid we’ve derived from foods.

It should be noted that in addition to the eight glass
recommendation, proponents of this advice usually footnote the statement by saying fluids containing alcohol or caffeine do not count toward the total daily amount of water consumed, regardless of their water content. This, they argue, is because caffeine and alcohol promote fluid loss through a diuretic effect on the body. But does it seem rational that consuming an 8-ounce beverage with mild caffeine or alcohol content could actually cause the body to lose fluid equal to, or more than, what that drink contains? If this were true, these types of fluids would cause an overall net loss of fluid in the body and dehydration.

After reviewing several reports released through the U.S. Department of Agriculture, the World Health Organization, and independent researchers, Valtin concluded that the recommendation to consume an additional glass of water when having an alcoholic or caffeinated beverage, simply does not “hold water.” Likewise, the Strength and Conditioning Journal acknowledges that caffeine does cause a loss of water in the body, but it is a fraction of what was just added. A cup of coffee can add at least two-thirds the amount of fluid to the body that a regular cup of pure water would supply in a person accustomed to regular caffeine intake.⁶

The Journal of the American College of Nutrition also reported the results of a small study that tested the effects of caffeinated beverages versus water on hydration status. The researchers of that study concluded that advising people to disregard caffeinated beverages as part of their total daily fluid intake was not substantiated by the results they found.⁷

The Institute of Medicine’s Food and Nutrition Board recently offered this to the debate: “While consumption of beverages containing caffeine and alcohol has been shown in some studies to have diuretic effects, available information indicates that this may be transient in nature, and that such beverages can contribute to total water intake and thus can be used in meeting recommendations for dietary intake of total water.’⁸

A final part of this inaccurate water message says that by the time our thirst signal alerts us we are thirsty, we are already facing dehydration. Just as in the previous case, applying rational thought to this would cause one to question that after years of human evolution, how could our internal alarm system for recognizing dehydration fail us so miserably?

Valtin reports that scientific studies have found just the opposite effect is true, and thirst is an early sign of dehydration.⁹ By measuring plasma osmolality (the concentration of solids in the blood), the extent of hydration can be determined. A change in plasma osmolality by less than 2 percent would elicit the thirst response. Furthermore, it would take a change in the body’s plasma osmolality by 5 percent to actually be considered dehydrated. This would mean that our internal alarm against dehydration works just as well as one would hope.

Millions of people, both male and female, are continuously plagued with chronic urinary dysfunction.¹⁰ The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says that more than half of men in their 60s, and as many as 90 percent in their 70s and 80s, have symptoms from an enlarged prostate. Although the NIDDK describes the symptoms of enlarged prostate occurring in older age groups, it is not uncommon for men in their mid-40s to come into our practice with complaints of urinating difficulty due to enlarged prostate. Additionally, the NIDDK says that more than 13 million people in the United States will experience urinary incontinence. Most of these cases will be as a result of stress or urge incontinence (a sudden, urgent need to urinate).¹¹

With so many people living with these conditions, it is possible to have multiple clients from these populations within a single massage practice. If you are routinely encouraging clients to consume at least eight glasses of water per day, exclude caffeine and mild alcohol from the overall total, and drink before they are thirsty, you may unknowingly be jeopardizing the health of those clients who live with a urinary dysfunction.

On the other hand, you might be the one needing to act cautiously when it comes to water consumption. Delayed urination as a result of environmental or work-related factors, coupled with excessive water intake, can lead to problems.

What Does It Mean?

It is important to thoroughly stress that consuming less than the current fluid intake recommendations is possible in a healthy population, living in a fairly mild climate and experiencing a lifestyle that is sedentary to mildly active. Some pathological conditions do appear to be controlled better with increased fluid intake such as chronic urinary stone formation and chronic renal failure. Indeed, within these small populations, I have seen recommendations to increase fluid consumption as part of the patient’s treatment.

The recommendations we have found successful within a sedentary, but healthy clientele are to drink when thirsty and adjust fluid intake according to increased heat and physical activity. If urinating too frequently, one may be drinking excessive fluid. If for any reason a person is combining excessive fluid intake with delayed urination, it is possible he is setting himself up for a dysfunctional bladder in the future. If symptoms of a bladder problem are suspected, see a urologist and ask if he or she specializes in voiding dysfunctions. Not all urologists specialize in this area.

Recently, the Institute of Medicine’s Food and Nutrition Board has undergone great efforts to clarify the 8 x 8 recommendation and establish a working reference for the amount of fluid needed daily. After an exhaustive review of research and national data, the board suggests an adequate intake (AI) value of 2.7 liters per day for women and 3.7 liters per day for men. This is based on the reported average fluid intake of a healthy, sedentary adult and has been set to “prevent deleterious, primarily acute, effects of dehydration.”¹² Included in their recommendations, the board says daily fluids can be obtained through the intake of all fluids including those found in caffeinated and alcoholic beverages and foods.

Although the road has been long, it seems we have come full circle and are close to the original recommendation offered by the Food and Nutrition Board in 1945 — the whole recommendation. For a healthy, albeit sedentary population, let thirst be the guide and obtain fluids from the foods you consume. And don’t forget both caffeine and alcohol, which when used in moderation, can contribute to daily fluid intake.

We obviously need sufficient water intake to maintain health and to nourish our bodies. Water is what sustains life. But the 8 x 8 mantra for water consumption may not be the best advice we can offer our clients or follow ourselves. So the next time someone tells you to indiscriminately push fluids or suffer the dire consequences, tell them their advice may well be “all washed up.”