Water: Can It Be Too Much of a Good Thing?

Dehydration is a familiar foe for endurance athletes. But did you know that drinking too much water can be potentially fatal, particularly if not treated properly? And you don’t have to be an elite athlete like a marathoner to fall victim to what doctors call water intoxication.

Water intoxication occurs when a person has consumed so much water that the salt levels in the blood become diluted, said Dr. Aaron Baggish, co-medical director of the Boston Marathon.

“When sodium concentrations are low in the blood, it actually allows water to leak out of the blood into the other tissues, a condition known as hyponatremia, added Baggish, who’s also associate director of the Cardiovascular Performance Program at the Massachusetts General Hospital Heart Center.

The brain appears to be the organ most affected by hyponatremia, and begins to swell as water leaks out of the blood and into brain cells, he said. Usually, the symptoms are mild, such as confusion, headache and nausea. But if left untreated, people might wind up suffering seizures, Baggish said. In the worst cases, the brain continues to swell uncontrollably, resulting in a potentially fatal condition called brain stem herniation, he said.

“The brain is soft tissue that’s contained in a fixed skull. When the brain swells, there’s one real way it can go as an exit path, and that’s down to the bottom of the skull where there’s a hole that connects the brain to the spinal cord,” Baggish said.

Death from water intoxication is very rare among athletes like marathon runners, said Dr. William Roberts, a former president of the American College of Sports Medicine.

“We’ve noted maybe a half dozen deaths out of probably 3 or 4 million finishers, so it’s not a very common cause of fatality,” said Roberts, who’s also a professor with the University of Minnesota’s Department of Family Medicine and Community Health. Marathon runners are more likely to die from a heart attack or heat stroke, he said.



Sports medicine doctors are much more likely to see cases of water intoxication or hyponatremia than family practitioners, Baggish said.

But endurance athletes aren’t the only ones at risk of water intoxication. A 17-year-old high school football player in Georgia died in 2014 after consuming too much fluid during practice. A 47-year-old British woman died from drinking too much water while hiking the Grand Canyon in 2008. And a 28-year-old California woman died of water intoxication after taking part in a radio station’s water-drinking contest in 2007 to win a video game.

Others at risk of hyponatremia: Older people who take diuretics and have reduced kidney function, said Roberts.

How much water does the average person need each day? The Institute of Medicine recommends that men consume 3 liters of fluids each day, women 2.2 liters.

My Take:
I prefer to separate water from other fluids and I don’t distinguish between male and female. So I recommend 2 liters of clean water per day, just over 2 quarts, as a base. Then increase that intake with equal amounts of water and electrolytes as your exercise activity increases.

So if I don’t exercise, I just need to drink the 2 liters of water. But if I go for a bike ride, I try to consume a half-liter of water and a half-liter of electrolytes every hour. I might increase that intake if it’s really hot.

The Bottom Line:
water intoxication is really not an issue for most of us. However, lack of clean water in the daily diet is often a problem. Monitor your water intake until you get in the habit of drinking 2 or more liters every day.

Source: November 3, 2016 National Institutes of Health