Water Intoxication

Too much water can be a problem for marathon walkers. Here's what you should drink before, during, and after.

To celebrate her 50th birthday in 2003, Carol Krucoff walked the 26.2-mile Reggae Marathon in Jamaica. The last detail she remembers from that day was crossing the finish line, and then vomiting. Krucoff awoke from a coma four days later at Duke University Medical Center, where an air ambulance service had flown her. The culprit? Hyponatremia, a low concentration of sodium in the blood caused by drinking too much fluid, be it sports drinks or H20.


"I'm fit. I used to run. I walk, lift weights, teach yoga, and yet I almost died from drinking too much water. It just was not on the radar screen when I trained for the marathon," says Krucoff, a seasoned health writer who also holds a black belt in karate. Today, Krucoff is fully recovered and eager to educate other walkers about the dangers of water intoxication.


The idea that marathoners would overhydrate is counter to conventional wisdom. "Consuming a lot of fluids was propagated by many people who thought they were giving good advice to drink, drink, drink," says John Cianca, MD, medical director of the HP Houston Marathon, which has cut its water stations by 50 percent. USA Track & Field spokesperson Jill Geer concurs. "It used to be to [continue to drink] to stay ahead of your thirst, but now the advice is to drink as you get thirsty," she says.A recent study reported in the New England Journal of Medicine (NEJM) revealed that overhydration may be a more common problem than previously acknowledged. Blood samples taken from 488 runners after the 2002 Boston Marathon showed that 13 percent had hyponatremia. And while less than 1 percent of study participants hit a critical level, this group is of greater concern to physicians because it can lead to seizures, coma, brain damage, and even death.


While the NEJM study focused specifically on runners, the three risk factors for hyponatremia that they identified can apply to walkers as well:


 gaining weight during the race

 a race time of over 4 hours

 a low body mass index (less than 20; normal being 20 to 25)


Researchers were also surprised to find that it did not matter whether the runners drank water or sports drinks. "It reemphasizes that it is not what you drink, but how much," says lead study investigator Christopher Almond, MD, a cardiac fellow at Children's Hospital Boston.


"This is especially good information for walkers," says Larry Kenney, PhD, professor of physiology and kinesiology at Penn State University, "because walkers are out there for a long time, which gives them an occasion to drink more." Marathon walkers are generally on a course for 6 or 7 hours as compared to the majority of marathoner runners who run the race in 4 to 5 hours.


Although the NEJM study identified both women and men as being at equal risk for hyponatremia, most data reveals that females carry a higher risk of suffering from extreme cases. But there is no consensus as to why. "We do have a good notion that it's attributable to anti-diuretic hormone levels in women, which may have to do with menstrual cycles," Cianca says. [pagebreak]Hyponatremia can develop slowly. But unless they are in big trouble on the course, most walkers with the condition will finish the race. Those with serious cases report headaches, dizziness, vomiting, and trouble breathing, explains Cianca.


The best strategy is to create a balanced hydration plan during training, one that aims to avoid both dehydration and overhydration. Here are some guidelines to follow:


Weigh yourself both before and after your training walks. "The goal is to match the amount of weight you lose in sweating with fluid intake," says Kenney. If you know you sweat one liter per hour, plan to drink about that amount while on the race course. For several hours following the race, drink 20 to 24 ounces per pound of weight lost to make up for the additional urine losses.


Weigh yourself before you start the marathon. The HP Houston Marathon and other races set scales at various places on the course so that participants can track their weight. If you weigh yourself ahead of time, you'll know if you are gaining or losing weight during the event.


Keep track of how much you drink before and during the marathon. Know what you drank before the event began, then count your intake as you go along. Figure out before going into the race how much water you should consume. "I hydrated like crazy beforehand, and drank at all of the water stops. But when I was asked how much I'd had to drink, I did not know," says Krucoff.


If you don't feel right--if you're slightly dizzy or have a nagging sense of being "off"--stop at a medical tent and ask to have your blood tested for sodium. The low normal end for sodium is 136. "Technically, if you are 135 or lower, you are hyponatremic. At 130 to 135, you recover pretty well if you are monitored," says Cianca. "Recovering requires getting rid of fluids by urinating. Between 125 and 130 can go either way; you can have a spontaneous recovery, or go downhill. We retest every 30 to 60 minutes, and while we don't always put an IV in, we are prepared to." Under 125 means a trip to the emergency room. Krucoff's sodium numbers were 117.


Study your hands. If they're puffy and your rings are tight, and you've drunk lots of fluids, taper off. Walkers often experience these sensations, so use common sense. Back off the water a bit.


Get acclimated. If the marathon is in a hot, humid climate compared to the one you trained in, go several days before the event to get accustomed to the weather.


Eat salty snacks. Have some pretzels before and after the race.


Count sports drinks as water. Don't think you're immune to hyponatremia just because you're consuming sports drinks. While they contain some sodium, it's not enough to avoid hyponatremia. For further information, you can read the paper on Exercise and Fluid Replacement or visit the US Track & Field Web site.
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