You’ve heard it a million times—“make sure to stay hydrated”—and if you’re a summer athlete than you’ve heard it even more. There seems to be a fascination with dehydration and the serious risks that come along with it, but you can have too much of a good thing.
According to Andy Blow, co-founder and Sports Scientist at Precision Hydration and a Red Bull High Performance partner, athletes and avid exercisers are most concerned with avoiding dehydration, but in reality over-hydration is actually a much more common problem.
"This can be especially problematic if athletes drink excessive amounts of low sodium fluids over several hours, usually immediately before and during an event and end up diluting the levels of sodium in their blood," says Blow "If it goes unchecked, this can result in hyponatremia, a potentially deadly condition where the brain swells due to having to absorb excess fluid from the blood."
Hyponatremia (also called water intoxication) doesn’t usually happen to healthy young people, but athletes taking in a lot of water in a short period of time run a high risk. A study published in the New England Journal of Medicine found that “hyponatremia occurs in a substantial fraction of non-elite marathon runners and can be severe.”
Athletes competing for hours at a time, especially in the summer heat tend to drink way more than they need, throwing their sodium levels off and creating a big problem. Without enough sodium to regulate fluid levels, the excess water seeps into the cells and causes swelling. When that swelling gets to your brain you need to seek immediate medical help, doctors can reduce swelling using salt water.
Another tricky part of hyponatremia is the list of symptoms and that’s because they mirror symptoms of heat stroke. With hyponatremia, you can be hot, sweaty, you might have a headache and sometimes there is nausea and vomiting—all things you might see in someone suffering from heatstroke. The major way to tell the difference is to know how much water you’ve had.
The best way to avoid over-hydrating, though, is simply to drink when you’re thirsty. If you're getting ready for a fitness event or an intense training session you can increase your fluid intake slightly and start the day before.
"In the final 48 hours before events and big training sessions we advise a lot of athletes to increase their fluid intake by an extra 500-750 ml or so on top of their normal intake with some extra sodium in it to help the body absorb more of this additional fluid without diluting the blood," says Blow.