In scores of road races around Maine this summer, the most dangerous part of the course might not be where you think.

It’s not the start, where runners might get tangled up and fall. It’s not the finish chute, where you see runners collapsing from fatigue.

The spot on the course that can put you at risk not just for injury, but for death? The water stops.

For years, commercials have advertised dangers of dehydration. We’re told that as we sweat we lose vital nutrients. We need to constantly replenish them, or else we will suffer consequences. One campaign is even more explicit. It goes like this: Hydrate or die.

So dehydration must be really dangerous, or even deadly, right? Wrong.

In all of the years physicians have been caring for athletes, do you want to guess how many athletes have died of dehydration? Over hundreds of thousands of events, millions of athletes and with millions of athletes competing, exactly zero have passed away from dehydration.

That’s right. No athletes have ever died because of dehydration. In fact, when modern marathons were first run at the turn of the 20th century, athletes were told not to drink at all over the 26.2-mile course.

Now, no modern sports medicine specialist would advocate that approach, but the point is clear: we can function well even when we are dehydrated.

Actually, overhydration is much more dangerous than dehydration. What’s the danger of drinking too much, anyway? Each year several athletes die of a condition called hyponatremia. It’s caused by drinking too many fluids so that the body’s salt stores become overly diluted. Hyponatremia can lead to confusion, coma, seizures, and even death.

The tragedy of athletic hyponatremia is that each and every case is entirely preventable. Athletes simply drink themselves to sickness, because they think they’re preventing dehydration.

In fact, studies show that there is no performance or health benefit to drinking in endurance events lasting less than about an hour. According to this, most runners would not need to rehydrate at all during a 5K road race. The same is true during training runs and other athletic situations.

Studies show that many athletes drink enough after their workouts to replenish all lost fluids. No matter how long the race or how hot the day, if you’re letting yourself drink when you’re thirsty, you will rehydrate. The point is, rehydration doesn’t need to happen all at once on the race course.

So think about hyponatremia the next time you pass the drink station at a road race. In most races, drinking every 2-4 miles is plenty. Grab a single cup at a time. Seek to drink enough to quench your thirst. If you’re not thirsty, don’t drink. 

Dr. James Glazer is a sports medicine physician for Coastal Orthopedics and Sports Medicine in Freeport. He serves as a consultant for the U.S. Ski Team.