For Marathoners, Carbohydrate Loading Is Not Enough
WebMD News Archive
May 5, 2000 -- Seven marathoners were admitted recently to an ER with
nausea, vomiting, mental confusion and pink, frothy fluid in their lungs. All
of them had the potentially fatal condition pulmonary edema, in which fluid
accumulates in the lungs. All but one of the patients were tested and treated
for excess fluid in the brain. The seventh patient was not tested for edema and
died from the fluid in the lungs and brain.
Doctors who studied these cases found that the main culprit was sodium loss
during intense exercise, causing the excess fluid to build up in the brain and
"Heat stroke isn't the only reason that runners collapse after
marathons," study author J. Carlos Ayus, MD, tells WebMD. "And if left
untreated, sodium loss can be fatal."
Ayus, a kidney specialist and professor at Baylor College of Medicine in
Houston, and his colleagues published their findings in the May issue of
Annals of Internal Medicine. They report that diagnostic tests showed
sodium losses of up to 13%. The patients were placed on ventilators and treated
with intravenous salt solution. Over 12 hours, lung fluid and brain swelling
decreased as sodium levels increased.
The authors believe low sodium first causes brain swelling, which then
causes a build up of fluid
in the lungs. "Doctors need to be aware of the association between these
two conditions," says Ayus, "because successful therapy depends on
During exercise, blood is directed from the stomach to the muscles, causing
ingested fluid to remain in the gut. After exercise, blood returns to the
stomach, allowing ingested fluid to be quickly absorbed by the bloodstream. But
because marathoners have sweated for hours, this high volume of fluid is often
low in sodium.
To prevent sodium loss, sports medicine experts advise sodium loading.
"Marathoners should use table salt before races, drink sports beverages
during races, and eat salted pretzels in the last half," says Lewis
Maharam, MD. Maharam, the medical director of two marathons and a board member
of the International Medical Marathon Directors Association, commented on the
study for WebMD.