Water Intoxication Affects More Than Runners And Triathletes
Is Hyponatremia Media Hype or Serious Public Health Concern?

Dr. Phil Maffetone

Drinking fluids during training and racing will soon be reaching a boiling point of controversy and not for reasons you might suspect. Dehydration, and how to keep it under control, is nothing new. What’s been bubbling up in the media for the past few years is hyperhydration—drinking too much and how it can lead to ill health and death. It’s also been called water intoxication. While the problem is usually associated with long hot races such as an Ironman triathlon, it can occur at any time given the right circumstances. Twenty-eight year old Jennifer Strange died in 2007 after competing in a Sacramento, California radio show contest to see how much water contestants could consume. The local coroner said her condition was consistent with water intoxication. The problem has become one of the more serious risks in certain sports, as over-hydrated marathoners, triathletes and ultra-endurance athletes have died during a race or right afterwards.

So what’s going on here? Because, as I will point out in this article, there soon might be limitations on the amount of water and sports drinks on race courses, with recommendations that athletes consume much less than what’s been encouraged for years. In fact, the recommendations of reduced water and sports drink intake already is emphasized in places like New Zealand and South Africa, where water intoxication is not nearly the problem compared to North America.

But there’s more to the issue. Certainly the sports drink and bottled water industry has pushed the recommendations that more fluid is better while sponsoring many races and individual athletes. An even broader view of the issue is that athletes themselves influence their risk of ill health and even death on race day in the way they train and the lifestyle they live. There’s even a relationship with muscle balance, gait and physical injuries. And, water intoxication comes with another serious, life-threatening condition called hyponatremia—low blood sodium. Looking at the problems of hydration and sodium regulation must be done holistically as many factors can be to blame.

  Photo: Timothy Carlson

Looking at the Research

Among the authorities who have shown that excess water intake can contribute to serious health problems is world-renowned endurance expert, researcher, and author, Professor Timothy Noakes, M.D., of the Sports Science Institute of South Africa. His recommendations of between 14 to 27 ounces of liquids per hour are much less than those of the American College of Sports Medicine (ACSM), which is 20 to 40 ounces per hour. My own general guidelines are specifically for healthy athletes to consume about 32 ounces per hour depending on the person, sometimes more since most athletes spill a considerable amount of water in the course of drinking it. This may be a key caveat: healthy athletes.

However, it’s important for each athlete to individualize his or her own needs, based on body size, the particular race environment, and level of fitness. Even more important is that, if you’re not healthy, racing is something to avoid since your risk of injury, worsening of health, and even serious emergency conditions, which can lead to death, are real consequences. The combination of water intoxication and hyponatremia is one grave example.

Improving your overall health, not just your fitness levels, and following some simple guidelines, such as not drinking to excess, can improve the body’s ability to regulate water, and its key electrolyte partner, sodium. Otherwise, you could gain weight during a long race and risk serious water and sodium imbalance.

Instead, endurance athletes are often encouraged to drink more during long training and racing. Much of this information comes from the very companies selling fluid replacement drinks, and often the same sponsors of races. The result is that, for many athletes it’s turned into an obsession—not just during races. Many athletes carry a water bottle on their bike for short rides, some during a run, and the majority cling to one at work or when driving. An ever-present water bottle has become like a pacifier for adult athletes.

Drink up! has been the recommendation for decades, not just in hot weather, where the loss of fluid is great, but during long events with cool or even cold temperatures.

Why so much confusion? Through the many years of telling athletes drinking more is better, the research has been showing we can really drink too much Gatorade and other fancy drinks, including water. The answer is that it’s a question of balance.

Proper hydration is key to this issue of not too much, not too little water. This means your fluid intake during a race should be about the same as your fluid loss.

Too Little = Dehydration

Fluid replacement is important during long races and training. It helps maintain blood volume, proper heart rate, blood flow in the skin to dissipate excess heat, and to prevent body temperature from rising too high, among other functions. A properly hydrated athlete will also subjectively feel the event is easier (a lower perception of effort), and will prevent the heart rate from climbing too high (a reflection of increased stress that will result in slowing down).

At the 2007 Chicago marathon, a shortage of water on a hot day suddenly became a problem for the back-of-the pack runners and long before the halfway point. Fearing health concerns from dehydration, race officials shut the race down for many runners.

It wasn’t too long ago that marathon courses and other long endurance events did not allow water stops or restricted fluids. During the 1904 St. Louis Olympic marathon, only one water stop was available, about midway through the course, although trainers did provide their runners with water along the way. Tour de France officials used to limit each rider to about two liters of water. But during races, riders raided roadside bars for refreshments, and filled their bottles from fountains.

In 1969 a study by C.H. Wyndham and N.B. Strydom entitled "The Danger of an Inadequate Water Intake During Marathon Running" (in the South African Medical Journal) may have been one of the triggers for new water recommendations, influencing international rule changes that would allow fluid intake—water stops—during endurance races.

By this point, Gatorade, created in 1965 for football players, began expanding into new markets—not just the world of jogging, which was becoming popular, but as a beverage for everyday use. The marathon craze in the 70s and 80s further fueled the interest in energy drinks. As more people were involved with marathons and triathlons, race fluids became more widely and readily available. For example, Bud Light was the Hawaii Ironman title sponsor in the early 80s, but afterwards it was Gatorade. The notion of “more is better” when it comes to fluid replacement was highlighted during race sponsorships. Most endurance events had an alliance with companies that sell sports drinks. This business relationship continues today as a billion-dollar industry. The main message of these companies to athletes—drink more!

Dehydration can be a serious health problem, and can even increase the risk of death. It can cause fatigue, nausea, weakness, muscle cramps, disorientation, slurred speech, and confusion. In the 1978 and ‘79 Hawaii Ironman events, race officials were concerned about safety, and so they instituted a weigh-in procedure. Triathletes were required to stop three times during the 112-mile bike section and once during the 26.2-mile run for body-weight measurements. These would be checked against one’s recorded pre-race weigh-in. If a racer’s weight went down by at least 10 percent, course officials would seek a mandatory withdrawal from competition.

But just six years later, the first published medical cases of a more serious problem for endurance athletes would be published—those that gained weight and had a severe drop in sodium. Too much water combined with low sodium would be shown to have serious and deadly consequences. Using the same weigh-in requirements today during the Ironman and similar races could save lives as the severity of the problem is usually associated with weight gain due to the high fluid intake and the body’s inability to regulate water and sodium. About 25 percent of Ironman finishers are found to have abnormally low blood sodium.

The problem of hyponatremia, usually combined with water intoxication, is now referred to as exercise associated hyponaturemia—EAH (usually defined by blood levels of sodium less than 135 mmol/liter). It shows up in athletes during or within 24 hours of their race or training. When EAH is more advanced, the problem can produce edema in lungs and the brain. This serious condition, called exercise associated hyponatremia encephalopathy or EAHE, despite being uncommon, is one reason why so much is being made of water intoxication. EAHE not only can produce alterations in mental status and respiratory distress, but seizures, coma and death.

   Photo: Timothy Carlson

Too Much = Water Intoxication

In 1985, Noakes and colleagues published a groundbreaking research paper in the journal Science and Medicine in Sports and Exercise, which described the occurrence of water intoxication, too much body water, and hyponatremia, low blood sodium, in four endurance athletes competing for over seven hours. When advised to drink less fluid, three of the athletes subsequently completed the same type event without problems. Since this study, other researchers have studied the issues of hyperhydration and hyponatremia in detail, along with its causes, and the misconception that more water is better. Its acceptance in the sports world—heavily allied with the sports drink and bottled water industry—has been slow.

In 2011, things have not changed too much. The acceptance of water intoxication, while mentioned in magazines and other media, has not always resulted in changes in race day encouragement of more fluid intake, although more medical directors at races are making the warning to not drink to excess. But a recent four-mile race in Sausalito, California, is an example of the continued promotion to drink more: their per-race literature boasts “several refreshment stations along the way”—with a water company as one of the sponsors. But for a four-mile fun run?

Even after a number of studies through the mid 1990’s clearly demonstrated that over-drinking could cause serious health problems—including death—the subject was nearly ignored by many in the sports medicine world. Noakes writes in the British Journal of Sports Medicine (2010) that, “Instead, in 1996, influential guidelines of the ACSM promoted the concept that athletes should drink ‘as much as tolerable’ during exercise. What followed was an epidemic of cases of EAH and its associated encephalopathy (EAHE).” The new ACSM guidelines almost a decade later were essentially maintained, as Noakes noted: “It is instructive to review the industrial connections of those who wrote the 2007 ACSM Position Stand. Of the six authors, four…have direct and longstanding involvement with Gatorade.”

Between 1993 and 2008, Tamara Hew-Butler and colleagues (in the Journal of Clinical Endocrinology and Metabolism, 2008) state that five marathoners, four of them female, died from EAH. (Studies show that women athletes may be much more vulnerable to EAH.)

EAH can produce symptoms of fatigue, mental disorientation, gait alterations, breathing difficulty—or no symptoms at all making it difficult to diagnose, and differentiate it from dehydration, without the help of a trained healthcare professional.

In a study compiling 2,135 endurance athletes who completed 42-kilometer marathons, 109-kilometer cycling events, and 226-kilometer Ironman triathlons (Proceedings of the National Academy of Sciences, 2005), Noakes found that about 60 percent were dehydrated while 11 percent were overhydrated. Overall, 6 percent had mild hyponatremia, and 1 percent had severe hyponatremia.

Athletes who gain weight during long races or training may be considered overhydrated. Those who lose more than about 3 percent body weight may be considered dehydrated. Today, EAH is considered one of the most common life-threatening complications of endurance exercise.

Now, we’re about to come full circle with new water and fluid recommendations for all athletes competing in endurance events. That is, if these guidelines aren’t shut down or lobbied against by the companies selling these products; they are often major sponsors of races and athletes. Regardless of whether it’s the cause or a contributory factor, excessive amounts of water intake can produce EAH and EAHE. So by restricting water and educating athletes to not drink excessively, these types of deaths can be prevented.

When it comes to drinking fluids, the tradition of “more is better” is not easy to break.

In a 2004 study of Ironman triathletes published in the British Journal of Sports Medicine, Karen Sharwood and colleagues concluded that, “There is a large body of literature that suggests that dehydration impairs performance and increases the risk of heat illness in ultra-distance races. However, these conclusions have been based on laboratory studies using exercise interventions of relatively short duration and are thus limited in their application to performance in the field.” Sharwood’s study was performed during the 2000 and 2001 South African Ironman Triathlon, and showed that there was no increased risk of heat illness associated with high levels of dehydration, and that high levels of weight loss do not significantly influence performance.

In fact, in some endurance events the top finishers showed some of the greatest loses of weight associated with dehydration. However, it’s impossible to say how much better any given athlete would perform without as much water loss. And, it can also be shown that even mild dehydration can impair muscle function. So the issue is not so simple if one wants to give general recommendation for all athletes.

What is simple is the concept of self-health management. It’s quite possible that those who develop water intoxication and hyponatremia may have reduced levels of health to start with, making them most vulnerable to water intoxication and EAH. In my recent email correspondence with Dr. Noakes, he agrees that those who develop EAH or EAHE must have predisposing health problems. In my clinical research, going back to the late 1970s, I found many athletes who had sodium regulation problems (usually the result of hormonal imbalance). From his data, Dr. Noakes says about 10 percent of athletes may be at risk for hyponatremia due to predisposition—add to that the overconsumption of water or sports drinks and serious consequences can follow.

Athletes should take control rather than let the sports drink market set the pace of fluid recommendations. Athletes should learn the optimal way to hydrate during a long race—drinking about the same amount of water that’s lost—and avoid using sports drinks as everyday beverages. Along with avoiding overtraining, and eating a proper diet, improvements in overall health helps assure proper hormone balance to better regulate water and sodium on race day—which can also contribute to a better performance.


When it comes to drinking fluids,
the tradition of “more is better” is not easy to break.


The sensation of thirst appears after a certain degree of dehydration, and this was always interpreted as meaning thirst is not the best indicator of fluid needs. In hindsight, this may indeed be the best indicator if mild dehydration is not an issue during competition.

Primary Causes of Water Intoxication and EAH

An athlete need not consume excessively high amounts of water to develop water intoxication—it can sometimes occur with lower volumes of water intake. That’s because among the real causes of the problem are 1) hormone imbalance, which reduces the ability of the body to properly regulate water; and 2) poor sodium regulation, itself controlled by other hormones. In particular, what’s referred to as the syndrome of inappropriate secretion of the antidiuretic hormone—SIADH—has been implicated as the main cause of EAH. This involves an important brain-body mechanism called the hypothalamic-pituitary-adrenal (HPA) axis, which produces various hormones and regulates water and sodium.

While we know that serious water and sodium problems can occur in athletes during long events, it’s a question of which came first—too much water, or body dysfunction that causes it. Perhaps a better question is this: Can excess fluid intake be an aggravating factor rather than the cause of water and sodium imbalance?

The answer to this question is “yes.” While restricting fluids could save lives, it would be treating the end-result problem and not the cause. Rather than asking all athletes to reduce their water intake during endurance races, especially in hot and dry conditions where dehydration can be a factor, it would be best to also determine which individuals are susceptible to the problems of water and sodium imbalances, and correct them. While preventing ill health and death is obviously of upmost importance, the cause of the problem must still be addressed. And, whether dehydration or EAH, the responsibility of prevention lies with each athlete.

With 25 percent of Ironman finishers showing abnormally low sodium, and my observations that many more endurance athletes show some signs and symptoms of overtraining—which can adversely affect the HPA axis— the number of individuals vulnerable to this problem may be quite high.

From a health and performance standpoint, the body has a great capacity to adapt to the possibility of higher or lesser amounts of water loss in the short term, such as during a race—a reason some athletes appear to function well despite significant (~ 3 percent) water losses. This adaptation occurs because of hormones produced in the brain and body that not only regulate water, but sodium in the blood. And, consuming reasonable amounts of fluid in a healthy body should maintain some degree of water and sodium balance. But this occurs in a healthy body.

Athlete Lessons from Non-Athlete Patients

Clues about athletic-associated water intoxication and hyponatremia can also come from the non-athlete population. The fact is everyone has an HPA axis that responds to physical, chemical and mental stresses. Chronic hyponatremia associated with dysfunction of the HPA axis is not uncommon in the general population, with SIADH the most common cause. In the U.S., three to five million people are diagnosed with hyponatremia annually, many without significant symptoms (to put this in perspective, the annual number of heart attacks is about a half million). In others, it can produce a wide range of problems including muscle dysfunction, irregular gait, impaired cognitive (brain) function, and bone loss. Even those with mild hyponatremia, nausea, vomiting and abdominal pain can result. While infections (tuberculosis, pneumonia), brain injury, cancer, and prescription medications (anti-depressants, anti-epileptic drugs, diuretics, certain anti-histamines) can significantly contribute to dysfunction of the HPA axis, many causes are unknown.

Hospitalized patients with hyponatremia have a significantly higher rate of mortality. The increased risk of death is even high in those with mild hyponatremia.

While many of these cases are found in those past middle age, young, seemingly healthy individuals can acutely develop water toxicity and hyponatremia through inadvertent recommendations. As described by the doctors from the Department of Emergency Medicine in Ankara, Turkey, a previously healthy 19-year-old female was brought to the emergency room with complaints of sudden-onset diffuse headache, nausea, vomiting, and progressive confusion. Symptoms developed almost two hours after a pelvic ultrasound, previously scheduled due to her menstruation irregularities. Before the test, she was asked to consume a high volume of water to fill the bladder. Her family reported that she consumed almost 3 liters of regular water in 1.5 hours just before the procedure. She was diagnosed with hyponatremia. Fortunately, she recovered well and was released from the hospital after 48 hours.

The Recipe for Disaster

Here are some key factors associated with overhydration and hyponatremia:

- Hormone imbalance, in particular the inappropriate secretion of ADH, which is produced in the brain’s pituitary gland and the hypothalamus, causes poor water regulation. ADH is the body’s primary regulator of water balance, informing the kidney to conserve or excrete water. Other hormones are involved as well.

- In this case, too much ADH, which can rise with the stress of a race, keeps the kidney from getting rid of water resulting in too much accumulating throughout the body. This results in weight gain.

- The HPA axis also regulates sodium via adrenal gland hormones. The result can be too much sodium loss with blood levels dropping to dangerously low levels.

- Normally, if blood sodium levels drop, reserves of this electrolyte (they’re especially high in bones) should help replace that which is lost, but for unknown reasons it does not occur in those with hyponatremia.

- Overdrinking of fluids before and during a race, beyond the ability of the kidneys to excrete excess fluid, further worsens the condition. At one time people relied more on common sense when it came to drinking water in a race—dry mouth, fatigue, calculating how much might be needed based on temperature, humidity, race pace, and how many more miles remain. But with the explosion of behavioral conditioning—constant advertising by companies selling fluid replacement drinks, and encouraged by race personnel—many athletes no longer rely on their brain’s natural instincts.

How can the adrenal glands, or the entire HPA axis become dysfunctional? These mechanisms, and the production of related hormones, are significantly influenced by day-to-day training, diet and nutrition, and other lifestyle factors. Excess stress in any of these areas—including overtraining and poor diet—may impair hormone balance contributing to improper regulation of water and sodium.

From the beginning of my coaching career, I paid careful attention to sodium and its role in health and sport performance. Some athletes seemed to lose too much sodium, and this problem was found to be associated with muscle dysfunction, and bone-related problems such as stress fractures and low bone density. Hormone imbalance was a common cause as indicated by measurements of the adrenal gland’s main stress hormone, cortisol. The cause of this was typically overtraining. As stress hormones increase, the levels of sex hormones fall, especially testosterone. This can further cause muscle, bone and other problems that impair health and performance.

Whenever an athlete began working with me, I would encourage him or her to not only focus on improving fitness, but health as well so that physical, chemical and mental injuries could be avoided. Many were initially found to have subtle or sometimes more obvious hormone imbalances that reflected an impaired HPA axis. These “subclinical” problems can separate a good athlete from a great one, or an average performance from a phenomenal one.


Some athletes seemed to lose too much sodium, and this problem was found to be associated with muscle dysfunction, and bone-related problems such as stress fractures and low bone density.


In addition to regulating water and sodium, and the stress of training and racing, the HPA axis is associated with blood sugar control, energy production and muscle function. In particular, muscle imbalance can parallel hormone imbalance, especially the HPA axis. It’s commonly known that gait irregularities are associated with hyponatremia. So a recipe for injury can be found in an athlete with muscle imbalance leading to gait irregularity and finally a local injury to a muscle or joint—along the way, reductions in performance also occur.

Balancing Your Brain and Body

Improving both health and fitness, including the balance of hormones associated with the HPA axis, is something that most athletes can accomplish on their own. In some cases, however, it may require assistance from an appropriate healthcare practitioner to help individualize a program for your particular needs.

The first step is to objectively evaluate your training and racing, stress, diet and nutrition, and all other lifestyle factors. Herein lies a potential problem. Objective self-assessment in a society where advertising influences ones ideas about all these factors—even more than the facts—is an issue that must be overcome. Connected with this are the many industry-influenced articles in magazines.

There are many lifestyle factors known to influence the HPA axis. As such, certain habits can help correct a problem, and maintain its function:

- Reduce training and racing stress. Many athletes train more miles than is necessary to obtain maximum benefits. In particular, too much anaerobic training, and racing too often can add undue stress.

- Physical treatment. Certain therapies can help reduce high stress hormones and improve the HPA axis. This involves finding the best therapy, and therapist, for your particular needs. Examples include certain biofeedback techniques, which involve relaxation and deep breathing, Swedish massage (a particular technique employed by massage therapists), and the natural treatment from sunlight stimulating the naked eye affecting the brain.

- Beware of chronic inflammation. It’s a relatively common problem in athletes, sometimes associated with death in a race due to a heart attack. Inflammation can also adversely affect the HPA axis.

- Diet and nutrition can significantly influence the brain and hormonal system. Too much refined carbohydrates in meals or snacks (not during a race) can over-stimulate the hormone insulin triggering other hormone imbalance and even inflammation. And, restricting calories, especially using low fat diets, can also contribute to chronic inflammation and disturb hormone balance.

Various clues can provide information that a given athlete may be vulnerable to hormone imbalance associated with an impaired HPA axis. This includes a history of bone fractures, osteoporosis or other bone injury. Others include waking in the middle of the night with difficulty getting back to sleep, increased body fat despite high levels of training, and muscle imbalance (which is often associated with many types of physical injuries).

By addressing physical, chemical and mental stress, athletes can significantly improve their overall health and fitness, with the result of better performances and lower risks of water and sodium dysregulation.

The recipe for disaster comes when an athlete has less than adequate health as reflected by hormone imbalance and poor sodium regulation; and then, if the athlete is encouraged to drink large amounts of fluids during an event, overhydration can occur along with hyponatremia.

A simple self-assessment could help determine those at high risk for water intoxication. Weighing yourself before and after a long hard training event or especially a race, can determine changes in body weight, which reflect losses or gain in water. Any abnormal changes—weight gain or loss of more than 3 percent— should be considered a red flag that requires further evaluation.

The serious problems of water intoxication and hyponatremia should also be put in perspective to other deaths that occur during endurance events. A study published in the British Medical Journal (2007) examined twenty-six U.S. marathons between 1975 and 2004. Over this thirty-year period, there were twenty-four sudden cardiac deaths confirmed, with twenty-one due to atherosclerosis, four from water intoxication and hyponatremia, two due to heart abnormalities, and one from heat stroke. Virtually all these deaths were preventable.

Healthy athletes who are properly trained tend to regulate their sodium and water very well, avoiding hyperhydration and hyponatremia. In an ideal world, it’s best for athletes to take responsibility for their own health to assure they lower their risk of serious illness and death, which will also help them reach their athletic potential.

   Photo: Timothy Carlson

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