The Drink-water-all-you-can Myth

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A lot of people tend instinctively to drink water when they start to sweat, believing that this will be the best solution to replenish the lost amount of fluid. But this is a very dangerous procedure for any age group. Drinking too much water can lead to a condition known as water intoxication and related problems resulting from the dilution of sodium in the body, hyponatremia. Water intoxication is most commonly seen in infants under the age of six months and sometimes in athletes. A baby can get water intoxication as a result of drinking several bottles of water a day or from drinking infant formula that has been too much diluted. Athletes can also suffer from water intoxication, as they sweat heavily, losing both water and vital electrolytes.
Hyponatremia, also called water intoxication, is generally the result of drinking extreme amounts of plain water which leads to diminished concentration of sodium in the blood. Once a rare occurrence at sporting events, it is becoming more prevalent as participation increases and more novice exercisers are entering endurance events without being aware of the drawbacks of this dangerous act!
Prolonged and excessive sweating increases the risk that an athlete will alter the fine balance of blood-sodium concentration. Because sodium is lost in sweat, it is important for those who exercise at high intensity for long periods of time to replace any loses, not only in form of plain water but also in terms of critical electrolytes!
Research has found that long duration endurance events, such as the Ironman distance triathlons, often have finishers with low blood sodium concentrations. Runners who drink extra fluids in the days before the race or those who stop at water stop during the race are at increased risk of hyponatremia. In fact, a study published in the New England Journal of Medicine (April, 2005) found that 13 percent of Boston Marathon runners developed hyponatremia from drinking too much water.
Causes of Hyponatremia
During high intensity exercise, sodium is lost along with sweat. An athlete who only substitutes the lost fluid with water will have a decreased blood-sodium concentration. As an example, consider a full glass of salt-water. If you dump out half of the contents of the glass (as is lost in sweat), and replace that with water only, the sodium concentration of in the glass is far less and the water is more dilute. This can occur in the bloodstream of an athlete who only performs rehydration with pure water during excessive sweating. The result is hyponatremia.
Adequate sodium balance is necessary for transmitting nerve impulses and proper muscle function, and even a slight diminution of this concentration can cause problems. Studies have shown that high intensity athletes can lose up to 2 grams of salt per liter of sweat. Replacing this during the event is critical to optimum performance and personal safety.
Symptoms of Hyponatremia
The early warning signs are often subtle and may be similar to dehydration and include nausea, muscle cramps, disorientation, slurred speech, and confusion. At this point, many athletes drink more water because they think they are dehydrated. Unfortunately, water alone will intensify the problem of hyponatremia, thus reinforcing the vicious circle. At the most extreme an athlete may experience seizures, coma, or death.
Treatment of Hyponatremia
At the first sign of symptoms an athlete should drink a sodium containing sports drink/electrolyte mixture or eat salty foods. Ideally, an athlete should plan ahead and estimate the expected fluid loss and need for sodium replacement during the event, and stay on a strict electrolyte hydration schedule during the race.
Preventing Hyponatremia
The best way for an athlete to avoid such problems is to plan ahead by training in the same conditions encountered during the race day. Hydration recommendations include –among others-using sodium containing sports drinks during long distance, high intensity events (more than 60-90 minutes long).In addition to this, salt intake should be augmented per day several days prior to competition (except for those with hypertension). On the other hand, one should avoid drinking more than the produced sweat and lost fluids.
Last but not least, one should keep in mind , that all athletes respond differently to exercise in terms of sweating and fluid loss; fluid and sodium replenishment needs will vary accordingly.
 
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