Water and Sodium Levels During Exercise – Can You Drink Too Much Water?

People who are exercising vigorously and/or in hot environmental conditions may lose as much as three liters of water and 3.5 grams of sodium per hour. Many people now drink large amounts of water to avoid dehydration and an increase in core body temperature while exercising, but sometimes this approach may do more harm than good.

Can a person drink too much water while exercising vigorously? What are the risks for developing and symptoms of exercise-associated hyponatremia (EAH)? How can people treat this potentially serious imbalance? Learn more about how to stay safe during rigorous and extended exercise.

Vigorous Exercise Can Lead to Sodium Loss - Photo by Dontworry at Wikimedia Commons

How Much Water Should You Drink During Exercise?

Recommendations for re-hydration during exercise have changed many times over the years. Early recommendations ranged from discouraging any intake of fluids during exercise to drinking as much as possible. Much of the current research is leaning toward a common sense approach in which people who are exercising should drink when thirsty to prevent dehydration, adjusting fluid intake for variables such as environmental temperatures, clothing, and the intensity of the workout.

Water has been hailed as a great choice of beverage, particularly for those who are attempting to decrease calories and lose or maintain weight. Many people are turning to water as a beverage of choice – bottled water sales tallies second only to soft drinks in the United States. WebMD offers an informative quiz on water that people may find very helpful.

Some studies have indicated that athletes may be more likely to drink an increased amount of fluids if they have added flavorings. The FDA now requires manufacturers of flavored water, water beverages with added electrolytes and/or nutrients, and similar water-containing beverages to list ingredients on the labels and to produce these beverages under sanitary conditions with quality control processes in place. Some sources indicate that people who are exercising may benefit from drinking some fluids with electrolytes added, but more research is needed in this area.

Over the years, previous endurance limits have been pushed, with many athletes going greater distances and attempting harder forms of exercise than ever before. Some folks are pushing their own limits by making fitness commitments to increase their activity drastically, and some careers place people in hot areas while exerting much energy over extended periods of time.

Although a more active lifestyle has the potential to improve one's overall fitness level, extremes in exercise combined with large amounts of water intake can be dangerous and even deadly if a person's sodium level drops to unsafe levels.

Causes of Hyponatremia Related to Exercise - Photo by Kencf0618 at Wikimedia Commons

What Causes Low Sodium Levels During Exercise?

Many folks know that exercise can cause blood sugar levels to drop, particularly in someone who has diabetes; however, exercise, particularly if the exercise is rigorous, can also change electrolyte levels. Electrolytes are minerals in the blood that carry an electrical charge. Examples of electrolytes in the body include sodium, potassium, magnesium, and calcium. Electrolytes in the blood can affect acid/base balance, fluid status, muscle functions, and many other vital body processes.

Serum sodium, the level of sodium in the blood, is an electrolyte that can be affected by exercise, water replacement, potassium levels, and several other factors. Normal ranges for serum sodium is 135 to 145 milliequivalents per liter (mEq/L). Table salt is sodium chloride, and many people are trying to lower dietary sodium with good reason. According to the CDC, many Americans eat a diet much higher than the upper limits of  2,300 mg/day; the recommended limit for sodium is 1,500 mg/day for those with hypertension or high risk for complications related to a diet high in salt.

Although too much salt can cause many long-term health problems such as high blood pressure, a sudden drop in serum sodium, called hyponatremia, can quickly become a medical emergency in the short term. Sodium levels can decrease via sweating when a person exercises vigorously or continuously over a long time, but the drop in levels appears to be more related to drinking large amounts of water, the body's inability to excrete the excess water by urinating, or a combination of those factors.

Exercise-associated hyponatremia (EAH) may also be called:

• Fluid overload
• Water intoxication
• Exertional hyponatremia
• Exercise-induced hyponatremia

Risks for Exercise-Associated Hyponatremia - Photo by U.S. Army at Wikimedia Commons

Who is at Risk for Exercise-Associated Hyponatremia?

Most people who drink water or sports drinks while exercising do not experience unusually low sodium levels, but others may experience moderate or even severe drops in serum sodium. Several people tend to be more likely to develop a dangerous drop in sodium levels associated with exercise, including:

• Women (perhaps due to size, an increased likelihood to heed recommendations to drink more fluids, or genetic factors)
• People who have smaller bodies and lower body weight
• Folks participating in continuous exercise over an extended period of time
• Those exercising in warm environments, particularly if the person is not acclimated to the warmer temperatures (although some athletes may experience hyponatremia while exercising in cooler environments as well)
• Those who drink large amounts of water before and/or during exercise (some have experienced hyponatremia when hydrating with fluids with added electrolytes)
• Slower athletes (probably due to added time exercising in order to finish the course and perhaps the intake of additional fluids during that time)
• Those with certain pre-existing health conditions such as people who are not able to excrete fluids efficiently or those who excrete higher than normal amounts of sodium in sweat, such as someone who is a carrier of the cystic fibrosis gene
• People taking certain medications that decrease sodium levels

Symptoms of Water Intoxication - Photo by Ceccomaster at Wikimedia Commons

What are the Symptoms of Exercise-induced Water Intoxication?

Many of the symptoms of exercise-associated hyponatremia result from fluid overload in the brain as brain cells tend to swell in an effort to compensate for the electrolyte imbalance. Unfortunately, many symptoms are non-specific and could be related to other exercise-related changes, such as a drop in blood sugar or dehydration.

Hallmark signs that the symptoms are more likely to be related to hyponatremia instead of other factors include:

1. The person has been drinking large amounts of fluids.
2. The person will typically experience weight gain during and/or at the conclusion of the athletic activity.
3. The person may become bloated or puffy around the ankles, fingers, and/or face. If the fluid settles in the lungs, pulmonary edema may result in which the person may experience coughing and shortness of breath that is worse if the person lies down.

Signs and symptoms of EAH are often related to swelling in the brain and may include:

• Fatigue and/or lethargy
• Stumbling or lack or coordination
• Muscle cramps, spasms, or weakness
• Nausea and/or vomiting
• Slurred speech
• Headache
• Changes in mental status
• Confusion or strange behavior
• Seizures
• Coma

Sodium levels do not necessarily correlate with the severity of symptoms with hyponatremia, but levels higher than 128 and below 135 mEq/L are less likely to result in swelling of the brain than levels below 128 mEq/L with resulting serious signs and symptoms. According to a 7/15/2005 Sports Medicine article, an athlete with a serum sodium level of 87 mEq/L survived while others with levels of 117 and 122 mEq/L died, indicating that the sodium level may not necessarily predict the outcome of this medical emergency. Symptoms also seem to be related to how quickly the sodium levels drop and tend to be more pronounced in those who are overhydrated rather than dehydrated.

Few people would have access to laboratory equipment used to measure serum sodium levels while exercising, so recognizing early signs and symptoms and seeking proper emergency care could be a life-saving measure for an athlete with dangerously low sodium levels. Symptoms of hyponatremia can progress quickly and have the potential to lead to serious symptoms, including death.

Treatment for Low Sodium - Photo by Danny Hayes U.S. Navy at Wikimedia Commons

How is Low Sodium Caused by Exercise Treated?

Prevention of hyponatremia can be quite complex. Most people participating in exercise do not exercise with such intensity or duration to necessitate preventive steps. Those who are at risk for EAH or who have experienced EAH in the past should speak with a qualified healthcare professional regarding an individualized preventive plan, which might include a variety of suggestions, such as:

• Exercising at a less intense level
• Exercising for shorter periods of time
• Decreasing the amount of fluids ingested before, during, and after exercise while being careful to avoid dehydration
• Drinking or eating electrolyte replacements specific to that person's needs

Because the symptoms of hyponatremia are often non-specific, many people mistakenly encourage an athlete with hyponatremia to drink more water. This only adds to the problem by adding to the fluid overload and dropping the serum sodium levels further.

Someone experiencing symptomatic exercise-associated hyponatremia should seek emergency medical care and avoid drinking additional fluids. Cases of symptomatic hyponatremia typically require in-hospital intervention with treatment focused on increasing the person's urine output in order to lower the serum sodium levels and decrease edema in the brain. Treatment usually includes administering intravenous fluids that have high high levels of sodium. One study mentioned the possibility of administering certain types of diuretics to correct EAH, but more research is needed to determine if this treatment would be ideal.

Drinking sports drinks and/or administering intravenous normal saline does not seem to adequately treat hyponatremia in athletes that are experiencing symptomatic fluid overload and may lead to continued hyponatremia and swelling in the brain. Some studies have demonstrated that fluids with added carbohydrates and electrolytes are associated with higher plasma levels of sodium when compared to distilled water, green tea, or flavored water during and after exercise.

Some studies have looked at having athletes participating in long-endurance exercise to drink or eat sodium replacement fluids that are higher than typical sports drinks, including pickle juice, dissolved bullion cubes, chicken noodle soup, or soup broth, but I could not find clear guidelines for administration of oral fluids with high volumes of salt. Oral replacement with a high sodium content might discourage some athletes to drink due to an unpleasant salty taste and could in turn lead to dehydration.

Water and Salt Levels During Exercise - Photo by Gabriel Martin U.S. Navy at Wikimedia Commons

Exercise and Low Salt Levels

I was prompted to research the topic of exercise-induced hyponatremia after a friend of mine experienced significant symptoms after exercising. She survived, thanks to the quick response of her husband and the great EMTs in the area, but a sudden drop in sodium levels can lead to serious health concerns and even death.

Exercising regularly has many benefits for one's body and well-being. Many people assume that if drinking a little bit of water is good that drinking lots of water will be even more beneficial; however, that is not always true when replacing fluids lost during vigorous exercise. Most people who exercise will not experience hyponatremia, but those who are at risk or who have experienced EAH previously would benefit from consulting a healthcare professional for an individualized exercise and re-hydration plan to meet their special needs.

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Sources (accessed on April 23, 2012 unless otherwise noted):

• Center for Disease Control and Prevention 02/23/2011 article "Water: Meeting Your Daily Fluid Needs"
• Journal of Athletic Training March/April 2009 article by Costas A. Anastasiou et. al. "Sodium Replacement and Plasma Sodium Drop During Exercise in the Heat When Fluid Intake Matches Fluid Loss" (accessed 04/24/2012)
• Journal of the American College of Nutrition 01/09/2006 article by Rick L. Sharp "Role of Sodium in Fluid Homeostatis with Exercise"
• MayoClinic July 14, 2011 article "Hyponatremia: Symptoms"
• National Institutes of Health 05/26/2010 article by David Zieve et. al. "Sodium in Diet"
• National Institutes of Health 09/20/2011 article by David C. Dugdale et. al. "Electrolytes"
• National Wildfire Coordinating Group 08/12/2005 safety bulletin "Appropriate Fluid Intake"
• Sports Medicine 07/15/2005 article by Louise B. Weschler "Exercise-Associated Hyponatremia: A Mathematical Review"
• U.S. Food and Drug Administration 04/13/2012 article "FDA Regulates the Safety of Bottled Water Beverages Including Flavored Water and Nutrient-Added Water Beverages"
• Wilderness Medical Society Spring 2001 article by Ian R. Rogers, MD, FACEM "Fluid and Electrolyte Balance and Endurance Exercise: What can we learn from recent research?"