Study Cautions Runners to Limit Their Water Intake

For those who aren't registered users on the NYTimes website, here is the text of the article in full.

--Jennifer

Study Cautions Runners to Limit Their Water Intake
By GINA KOLATA

fter years of telling athletes to drink as much liquid as possible to avoid dehydration, some doctors are now saying that drinking too much during intense exercise poses a far greater health risk.

An increasing number of athletes - marathon runners, triathletes and even hikers in the Grand Canyon - are severely diluting their blood by drinking too much water or too many sports drinks, with some falling gravely ill and even dying, the doctors say.

New research on runners in the Boston Marathon, published today in The New England Journal of Medicine, confirms the problem and shows how serious it is.

The research involved 488 runners in the 2002 marathon. The runners gave blood samples before and after the race. While most were fine, 13 percent of them - or 62 - drank so much that they had hyponatremia, or abnormally low blood sodium levels. Three had levels so low that they were in danger of dying.

The runners who developed the problem tended to be slower, taking more than four hours to finish the course. That gave them plenty of time to drink copious amounts of liquid. And drink they did, an average of three liters, or about 13 cups of water or of a sports drink, so much that they actually gained weight during the race.

The risks to athletes from drinking too much liquid have worried doctors and race directors for several years. As more slow runners entered long races, doctors began seeing athletes stumbling into medical tents, nauseated, groggy, barely coherent and with their blood severely diluted. Some died on the spot.

In 2003, U.S.A. Track & Field, the national governing body for track and field, long-distance running and race walking, changed its guidelines to warn against the practice.

Marathon doctors say the new study offers the first documentation of the problem.

"Before this study, we suspected there was a problem," said Dr. Marvin Adner, the medical director of the Boston Marathon, which is next Monday. "But this proves it."

Hyponatremia is entirely preventable, Dr. Adner and others said. During intense exercise the kidneys cannot excrete excess water. As people keep drinking, the extra water moves into their cells, including brain cells. The engorged brain cells, with no room to expand, press against the skull and can compress the brain stem, which controls vital functions like breathing. The result can be fatal.

But the marathon runners were simply following what has long been the conventional advice given to athletes: Avoid dehydration at all costs.

"Drink ahead of your thirst," was the mantra.

Doctors and sports drink companies "made dehydration a medical illness that was to be feared," said Dr. Tim Noakes, a hyponatremia expert at the University of Cape Town.

"Everyone becomes dehydrated when they race," Dr. Noakes said. "But I have not found one death in an athlete from dehydration in a competitive race in the whole history of running. Not one. Not even a case of illness."

On the other hand, he said, he knows of people who have sickened and died from drinking too much.

Hyponatremia can be treated, Dr. Noakes said. A small volume of a highly concentrated salt solution is given intravenously and can save a patient's life by pulling water out of swollen brain cells.

But, he said, doctors and emergency workers often assume that the problem is dehydration and give intravenous fluids, sometimes killing the patient. He and others advise testing the salt concentration of the athlete's blood before treatment.

For their part, runners can estimate how much they should drink by weighing themselves before and after long training runs to see how much they lose - and thus how much water they should replace.

But they can also follow what Dr. Paul D. Thompson calls "a rough rule of thumb."

Dr. Thompson, a cardiologist at Hartford Hospital in Connecticut and a marathon runner, advises runners to drink while they are moving.

"If you stop and drink a couple of cups, you are overdoing it," he said.

Dr. Adner said athletes also should be careful after a race. "Don't start chugging down water," he said.

Instead, he advised runners to wait until they began to urinate, a sign the body is no longer retaining water.

The paper's lead author, Dr. Christopher S. D. Almond, of Children's Hospital, said he first heard of hyponatremia in 2001 when a cyclist drank so much on a ride from New York to Boston that she had a seizure. She eventually recovered.

Dr. Almond and his colleagues decided to investigate how prevalent hyponatremia really was.

Until recently, the condition was all but unheard of because endurance events like marathons and triathlons were populated almost entirely by fast athletes who did not have time to drink too much.

"Elite athletes are not drinking much, and they never have," Dr. Noakes said.

The lead female marathon runner in the Athens Olympics, running in 97-degree heat drank just 30 seconds of the entire race.

In the 2002 Boston Marathon, said Dr. Arthur Siegel, of the Boston Marathon's medical team and the chief of internal medicine at Harvard's McLean Hospital in Belmont, Mass., the hyponatremia problem "hit us like a cannon shot" in 2002.

That year, a 28-year-old woman reached Heartbreak Hill, at Mile 20, after five hours of running and drinking sports drinks. She struggled to the top. Feeling terrible and assuming she was dehydrated, she chugged 16 ounces of the liquid.

"She collapsed within minutes," Dr. Siegel said.

She was later declared brain dead. Her blood sodium level was dangerously low, at 113 micromoles per liter of blood. (Hyponatremia starts at sodium levels below 135 micromoles, when brain swelling can cause confusion and grogginess. Levels below 120 can be fatal.)

No one has died since in the Boston Marathon, but there have been near misses there, with 7 cases of hyponatremia in 2003 and 11 last year, and deaths elsewhere, Dr. Siegel said. He added that those were just the cases among runners who came to medical tents seeking help.

In a letter, also in the journal, doctors describe 14 runners in the 2003 London Marathon with hyponatremia who waited more than four hours on average before going to a hospital. Some were lucid after the race, but none remembered completing it.

That sort of delay worries Dr. Siegel. "The bottom line is, it's a very prevalent problem out there, and crossing the edge from being dazed and confused to having a seizure is very tricky and can happen very, very fast," he said.

Boston Marathon directors want to educate runners not to drink so much, Dr. Siegel said. They also suggest that runners write their weights on their bibs at the start of the race. If they feel ill, they could be weighed again. Anyone who gains weight almost certainly has hyponatremia.

"Instead of waiting until they collapse and then testing their sodium, maybe we can nip it in the bud," Dr. Siegel said.

I always find it interesting when running in prospect park (3.3 mile loop) the number of walkers with fuel belts on filled with gatorade or some other colorful beverage. yet almost everyone else that is running doesn't have any fluids with them. the key point in the article says those that take over 4 hours to complete a marathon are the ones overhydrating. My theory is that they read lots of articles that faster runners are reading and feel that the same applies to them when in fact they aren't sweating nearly as much as someone running at a faster clip. plus, there are water fountains in a few places, so you don't have to carry anything with you, really.

Yikes. Thank you for posting.

This is all so confusing, I think I have to read it again. I love drinking water!

But did you sleep at a Holiday Inn Express last night?

Great article and follow up thoughts...thanks to all

Here's a handy dandy calculator that does what Karl suggests:

http://www.powerbar.com/Products/Beverage/Hydration/HydraCalc/index.asp?pt=he

That page also has a link to the USATF's guidelines on hydration and other additional readings.

http://www.usatf.org/groups/Coaches/library/hydration/

Edited by the bear 2005-04-14 11:49 AM

I have assigned this as an in class reading for my anatomy and physiology classes today. It has sparked some great discussions and has been an eye opener for them. It has allowed for me to bring back some learning on homeostasis and hormones like ADH etc.

So I guess my old football coach was right - salt tablets before a hard workout. 

From the actual study:

We could find no association between the composition of fluids consumed and hyponatremia. This finding probably reflects the relative hypotonicity of most commercial sports drinks, which have a typical sodium concentration of 18 mmol per liter, less than one fifth the concentration of normal saline. Although it is difficult to rule out some effect of the type of fluid consumed on the risk of hyponatremia, our findings suggest that the contribution of the type of fluid is small as compared with the volume of fluid ingested.

And:

The data from the present study suggest that hyponatremia associated with the running of marathons — and more broadly, with high-endurance exercise14,15,21,22,23 — may be a preventable condition. One relatively simple strategy to reduce the risk would be for runners to weigh themselves before and after training runs to gauge the effectiveness of their overall hydration strategy and adjust their fluid intake accordingly. This could be particularly useful during long training runs in which the distance and duration most closely approximate those of an actual marathon. Because runners vary considerably in size and in rates of perspiration, general recommendations regarding specific volumes of fluids and frequencies of intake are probably unsafe and have been superseded by recommendations favoring thirst or individual perspiration rates as a primary guide.20,24 Sporadically checking their weight could be a relatively easy way for runners to determine whether their current hydration strategy puts them at undue risk for the development of hyponatremia.

I think the key to this article is speed.  A regular marathon time is less than three hours. In that time you really don't have time to drink a lot. But if you're slow like me then a marathon may be five or six hours. That's plenty of time to dawdle. And if you drink while' you're dawdling then that's like walking around drinking cup after cup of water when the effort you're exerting isn't more than say walking a little fast. Just because you go longer doesn't mean you're enduring anything. Anyone can walk 26 miles. You need hydration, salt, performance enhancers to run 26 miles in less than three hours. You need to guard against dehydration when speed is involved not just effort. I always thought it was strange that I didn't drink very much during my sprint tris. In fact I hardly drank at all. Drank some on the bike but less than 12 oz and none on the run and on the swim only what water I swallowed at the start. Now that I'm doing a 1/2IM I'm swimming, biking and running longer and I still drink relatively little. Like today I did a 6 mile bike and a 7 mile run and only had one 12 oz Gatorade the entire time for both exercises. Didn't feel thirsty at all. So I just find it interesting that the overhydration came on when more "normal" people began doing long endurance events.

This isn't exactly new info, but important.  a pound lost roughly equals a liter of fluid lost.  How much you sweat (regardless of how fast you are going) and how much sodium is in that sweat is a huge factor and varies from person to person.  I am VERY slow but sweat like crazy (a pound a mile in the heat). Last months inside triathlon was devoted to hydration and gave a lot of helpful info.   Carl is right about the sports drinks  Most of them don't have enough sodium if you are a heavy sweater. 

Also, the one doc mentioned in the NYT article sounds like a quack. He said , "no one has ever died from dehydration." Well, technically, that may have some truth to it, but people die not infrequently from heat stroke which happens when your body exhausts its ability to regulate its temperature by sweating. There have been many high profile sports and Army deaths because of it.

Finally, the article said that medics & docs make people sicker by giving them fluids...well, they give salty fluids so that comment is a little questionable also. And makes me question the expertise of the physician making the statements.

The April issue of Inside Triathlon's feature story addressed Hydration. Very interesting info. Wish I could find a link to the article online somewhere.

It also had an interview with Scott Molina about his trial and error in determining his own personal hydration needs (apparently he sweats about 3x the normal rate).