Keeping hydrated is important when exercising, but drinking too much can be hazardous - in some cases even resulting in death. A panel of experts has published new guidelines to avoid fatal overconsumption of fluids, recommending that athletes only drink when they are thirsty.
Too much water or sports drinks can lead to a condition called exercise-associated hyponatremia (EAH), whereby the kidneys are unable to excrete the excess water in the body completely. As a result, the sodium in the body becomes diluted, causing dangerous swelling in cells.
While mild symptoms of EAH include dizziness, nausea and puffiness, in severe cases the condition can lead to confusion, seizures, coma and even death. At present, at least 14 athletes are estimated to have died as a result of EAH.
According to the authors, it is not just athletes engaging in strenuous exercise such as hiking and marathons that are susceptible to the condition. Cases have also been reported among people participating in lawn bowls and yoga.
The new 2015 EAH Consensus Guidelines, published in the Clinical Journal of Sport Medicine, suggest that there is a simple way for athletes to avoid these risks - just follow the natural thirst stimulus when it comes to drinking.
"Using the innate thirst mechanism to guide fluid consumption is a strategy that should limit drinking in excess and developing hyponatremia while providing sufficient fluid to prevent excessive dehydration," the authors state.
Many experts recommend drinking more water than usual in hot weather to improve the body's chances of keeping cool and reducing the risk of heat-related illness like heat cramps and heat stroke. Several groups have previously advised against waiting until feeling thirsty before drinking.
However, the authors state that this advice is largely meant for situations where people sweat much more frequently, and that the advice has helped foster the idea that thirst is a poor guide for knowing when to drink.
"Muscle cramps and heat stroke are not related to dehydration," says panel member Dr. James Winger, an associate professor in the Department of Family Medicine of Loyola University Chicago Stritch School of Medicine. "You get heat stroke because you're producing too much heat."
Drinking when not thirsty is 'potentially disastrous'
According to Dr. Winger, modest to moderate levels of dehydration can be tolerated by otherwise healthy athletes, with athletes capable of losing up to 3% of their body weight while exercising due to dehydration and it not compromising their performance.
Writing in an associated editorial, panel member Dr. Mitchell H. Rosner, from the Division of Nephrology at University of Virginia Health System, states that inaccurate statements can lead to dangerous behaviors and subsequent EAH:
"In all cases, blanket statements that can be found on the Internet such as 'don't wait until you feel thirsty' make little sense for the majority of casual athletes and have the potential for disastrous consequences as they promulgate the idea that near constant fluid ingestion during athletic events is a reasonable and even necessary thing to do."
The authors of the guidelines also discuss how EAH can be treated. They state that a concentrated 3% sodium solution - three times the concentration found in regular saline solution - can be used to treat severe life-threatening cases.
They also recommend that prospective and clinical trials should be conducted in order to assess the success of the "drink to thirst" strategy, along with further research into whether EAH increases the risk of long-term health problems and whether there are genetic markers that give people a predisposition toward the condition.
For Dr. Rosner, the immediate goal is that no other athletes die from EAH. "The consensus group feels that EAH is completely avoidable and with training and education regarding safe drinking/hydration that this goal is achievable," he concludes.
Previously, Medical News Today reported on research that suggested extreme levels of exercise could lead to blood poisoning.