I’ve been a runner for a number of years. Rain, sleet, snow—or hot summer—I try to get my runs in on a regular basis. Where I live the heat can be oppressive in the summer, so I try to be very sensitive to the signals my body sends.
But many other people who work out frequently ignore what their bodies tell them. And research at the Loyola University Medical Center shows that there’s one common instance where not paying attention to bodily sensations can kill you.
The problem, which may worsen in the summer, starts when exercisers start drinking a lot of water because they have been told they need to be super-hydrated in hot weather.
In fact, drinking too much water, or even too much of a sports drink, say the scientists at Loyola, can be fatal. And they have documented 14 instances where a condition called hyponatremia, which happens when you drink too much water or sports drinks, has killed runners, football players and other athletes.
They say you should only drink when you feel thirsty. Even in hot weather.
“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,” warn the researchers.
If you are exercising and you drink too much water, you can overwhelm your kidneys to the point they become unable to filter out enough water from your blood. That ends up diluting the body’s supply of sodium, causing your cells to swell. And that’s a condition that can kill.
Unfortunately, exercisers are frequently told to drink plenty of fluids even if they are not thirsty. Sometimes the advice is to drink a large amount to fend off heat stroke, fatigue or muscle cramps.
But over-drinking won’t stop those conditions and can be very dangerous.
“Muscle cramps and heatstroke are not related to dehydration,” says researcher James Winger. “You get heat stroke because you’re producing too much heat.”
He adds that it is OK to be mildly dehydrated when you exercise and it is not risky. You can lose up to about 3 percent of your body weight while exercising without having it compromise your performance.
So if you’re thirsty, by all means drink some water. When my body communicates that need to me, I’ve got my water bottle ready. I prefer to fill it with coconut water quite often because it also provides the potassium most Americans don’t get in their diet.
But if you don’t feel thirsty, you can safely wait to take in fluids later. Remember, your body usually knows best about what it needs when you’re hot and sweaty. Just listen.
