Can Athletes Drink Too Much Water?
It seems as if we could never drink enough water. After all, aren't we always being told to drink more water?
That's not always the case for ultra-endurance athletes who spend long hours exercising. Sometimes, drinking too much water can actually be a problem. If they flood their bodies with excess water, thus lowering their sodium levels, in rare cases, they may fall victim to a potentially fatal condition called hyponatremia.
Experts define hyponatremia as low sodium concentration in the body, specifically the extra-cellular fluid which is the blood and the fluid around the body's cells. "When someone becomes hyponatremic, their sodium level falls below normal," says Amy Roberts, Ph.D., sports scientist at the Boulder Center for Sports Medicine in Boulder, Colorado.
Normal sodium levels run between 135 and 145 milliequivalents per liter (mEq/L), says Lawrence E. Armstrong, Ph.D., professor of exercise and environmental physiology at the University of Connecticut. Hyponatremia is clinically diagnosed at 130 mEq/L or below.
What Causes Hyponatremia?
Because the condition cannot be safely duplicated in laboratory studies, little is known about the causes of hyponatremia. Armstrong says experts have three main theories. A fourth exists but it is little more than a combination of the three.
- Theory #1: The extra-cellular fluid becomes diluted because the sweat volume and the sweat sodium concentration are very high, Armstrong says.
- Theory #2: An anti-diuretic hormone known as AVP (arginine vasopressin), a hormone that causes the body to retain water in the urine and extracellular fluid, reduces sodium levels. AVP secretion causes water retention so that rather than losing fluid, people retain it, Armstrong explains.
- Theory #3: Armstrong supports a third theory which proposes that sodium losses are moderate or normal in sweat and urine. "Yet because a large volume of water or diluted fluid is consumed and subsequently retained in the body," he says, "the sodium concentration of the blood is reduced to critical levels."
When sodium concentration in the blood is critically low, symptoms like muscle weakness, disorientation, headache, fatigue, and nausea may occur. The most severe symptoms include seizures, respiratory arrest, coma, and death.
When Does Hyponatremia Happen?
Several conditions have to be present for hyponatremia to occur.
First, the athlete has to be sweating. So it's more likely that this will happen in hot, humid environments rather than hot, dry climates, Roberts says.
By far, though, the most important factor is the duration of the activity. Recreational athletes aren't likely to experience hyponatremia, or what's also known as water intoxication. "Hyponatremia is overdramatized," says Mark Baugh, Pharm.D., author of Sports Nutrition: The Awful Truth (see Resources below). "Unless you're in a sport where you just have to keep running for hours to win the race, you're not going to have this problem."
Who Is Most at Risk for Hyponatremia?
Ultra-endurance athletes who enter such events as 100-mile races and Ironman competitions are most at risk. Baugh says that hyponatremia can occur as early as four hours into an event, but it's more likely to happen after six, eight or 10 hours of exercise. Even then, it's a rare occurrence. In a race of 1,000 runners, there might only be one or two athletes who develop clinical symptoms of hyponatremia, Armstrong says.
One of the few evaluations of hyponatremia in ultra-endurance athletes was conducted on Hawaii Ironman competitors between 1985 and 1989. Experts concluded that 29% of the athletes were hyponatremic, but they were diagnosing hyponatremia as having a blood sodium level greater than 130 mEq/L. As mentioned earlier, clinical diagnosis of hyponatremia is 130 mEq/L and below. In addition, little research had been conducted about fluid intake during long events, so most athletes drank water or defizzed soda, Armstrong says. Today, athletes are smarter about what and how to drink.
Brad Musser, M.D., worked at the Hawaii Ironman Triathlon in 1999 as a volunteer at the medical tent. He knows of only one woman who was diagnosed with hyponatremia during the event. She was brought into the medical tent almost unconscious. Her sodium level had fallen to 124 mEq/L.
How Can Ultra-Endurance Athletes Prevent Hyponatremia?
Ultra-endurance athletes need to take preventive measures to head off hyponatremia.
- Say yes to salt
- Baugh suggests that these athletes salt their food more than the average person. "Don't be shy with the salt," he says. "Start with a good supply of sodium in your body." (Recreational athletes, don't fear. Armstrong says the U.S. diet adequately supplies the amount of sodium lost in sweat.)
- Choose drinks wisely
- Just like recreational athletes, ultra-endurance athletes are encouraged to drink water before their events, but once they've been exercising for more than an hour, sports drinks or other fluids with sodium are better choices. "The whole goal is to replace water at the exact rate that it's being lost and to add sodium to that ingested fluid," Roberts says. That's hard, though, because most people become thirsty after they're already dehydrated.
- Weigh in
- Athletes should weigh themselves before, during, and after ultra-endurance events. "The safest way to consume fluids is not to overdrink and not to underdrink," Armstrong says, adding that in most cases, dehydration is more likely to be a problem than hyponatremia. By weighing themselves, athletes will know if they're drinking too much or too little.
Armstrong recommends checking body weight at the same time every day before and after an ultra-endurance event. Doing this will help athletes gauge how much fluid they need to replace or if they've consumed too much fluid. For every pound lost, they should drink one pint of fluid. As Armstrong says, citing a popular phrase, "A pint's a pound the world around."
Cheers,
Eve :-)
Comments