Lacing up your running shoes to run a marathon this spring? You might experience an unseen injury. A small study published Tuesday in the American Journal of Kidney Diseases shows marathon running can cause acute kidney injury, but that doesn’t mean you should skip long-distance races yet.
“The short-term acute kidney injury is pretty pronounced. But since these participants are healthy, they are recovering very well,” said Dr. Chirag Parikh, professor of medicine at Yale University and Veterans Affairs Medical Center, and an author of the study.
Parikh and his colleagues looked for signs of acute kidney injury — by examining serum creatinine levels, kidney cells, and proteins in urine — from 22 people running the 2015 Hartford Marathon. The researchers took measurements the day prior to the run, immediately after the race and 24 hours later.
Right after the marathon, 82 percent of the runners showed acute kidney injury, but it started fading a day later.
"Kidney injury is very common in this population," said Dr. John Kellum, director of the Center for Critical Care Nephrology at UPMC in Pittsburgh, who wasn't involved in the study. "We had known and suspected some degree of kidney dysfunction in people undertaking long runs and marathons."
Kellum said experts believed that muscle breakdown from strenuous exercise caused the acute kidney injury, but this study finds that's not true. The researchers theorize that physical stress causes the injury. A mix of an increase in core temperature, dehydration, and decreased blood flow to the kidneys likely contributes to the short-term harm.
While acute kidney injury seems unavoidable when it comes to marathon running, Parikh says people can avoid more serious cases by staying well hydrated and skipping common pain relievers known as non-aspirin nonsteroidal anti-inflammatory drugs (NSAIDs) because they can have a toxic effect on the kidneys.
“If someone is not well hydrated, they can end up getting more severe acute kidney injury,” he said. “It is unlikely that it can prevent it because it is happening because of physical stress. Chances are it can only help to alleviate response.”
RELATED: How healthy is running for you?
Most people are unaware they have acute kidney injury because they don’t experience noticeable symptoms.
Parikh remains unsure if running in warmer climates puts people at a greater risk of acute kidney injury. He also says the runners don't appear to experience long-term kidney problems. Study participants had been running for at least a decade and completed several marathons a year, yet the researchers couldn’t detect long-term harm.
“We do not know if there is small kidney damage that is not picked up,” Parikh said. “We don’t know if they will have problems in 20 years.”
Yet, he doesn’t believe people should stop running.
“I don’t want people to get alarmed,” he said. “It is kind of this unknown territory. 'What is the right amount of running?'”