Dehydration vs. Overhydration
Advice about preventing dehydration is especially prevalent during the hot summer months when the amount of fluid lost through sweat can reach dangerous levels. There is another danger related to hydration that is lesser known, hyponatremia, a potentially fatal condition that can result from drinking too much water.
When too much water is consumed, sodium levels can reach dangerously low levels, leading to a condition known as hyponatremia. Endurance athletes are at a particularly high risk for hyponatremia, also called "water intoxication" or exercise associated hyponatremia. In a 2002 study of 488 Boston Marathon runners, 13 percent had hyponatremia at the end of the race.
How Hyponatremia Occurs
Hyponatremia occurs when there is an imbalance between the amount of water and sodium in the body. Consuming too much water while losing too much sodium through sweat makes it difficult, if not impossible, for the body to use the water it has. It is possible, in this case, to be dehydrated, yet drowning your body with water. The result is collapse, convulsions or death.
Warning Signs of Hyponatremia
If too much water is consumed during prolonged exercise, there are warning signs that let you know you could be headed for the medical tent rather than the finish line. Nausea, vomiting, disorientation, headache, muscle weakness and feeling bloated are signs that you may be overhydrated. Another warning sign is the feeling that you can't take in any more water, yet also can't urinate. It is important to seek immediate medical attention if you experience any of these symptoms after an endurance event or after a long training run.
Risk Factors
Excessive consumption of fluids is one of the main contributing factors leading to this condition, but there are additional risk factors, such as being at either end of the body-mass index (either too thin or too heavy), taking longer than four hours to finish a race, and the tendency to gain weight during a race. Females are at higher risk than males. Are you a salty sweater? Odds are you lose more sodium through perspiration, putting you at higher risk for exercise-associated hyponatremia.
How Much Water Is Too Much?
Research in the area of hyponatremia is ongoing, but experts recommend that during endurance events, such as marathons, you drink only when thirsty, and only enough to maintain proper sodium balance rather than to maintain body weight. Also, consume sports drinks, which have sodium and potassium in them, instead of regular water.
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