The Grapevine

Is Running A Marathon Bad For Your Body? Physical Stress From Long-Distance Running May Damage Kidneys

A little running goes a long way when it comes to our health. Regardless of our duration or speed, a few minutes of running can significantly reduce our risk of death. But, how much running is too much?

Researchers at Yale University in Connecticut have found marathon running can cause an unexpected health risk: acute kidney injury. Over 80 percent of runners who finished marathons experienced injury comparable to patients who are in intensive care or those who undergo surgery.

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"The kidney responds to the physical stress of marathon running as if it's injured, in a way that's similar to what happens in hospitalized patients when the kidney is affected by medical and surgical complications," said Dr. Chirag Parikh, study author and professor of medicine at Yale and his colleagues, in a statement.

Generally, exercise is good for the kidneys, especially cardio, including walking, cycling, and jogging. Aerobics help prevent the number one cause of kidney failure — type 2 diabetes, and other leading causes, such as high blood pressure and cholesterol. For example, a 2008 study in the Clinical Journal of Sport Medicine found those who exercised daily had lower levels of  creatinine — a waste product — and their kidneys were better able to clear creatinine from their bloodstream.

However, when we exercise too much, over three hours per day, our body begins to shut down. When we exhaust our bodies, and don't add calories to the ones we've burned, our kidneys aren't able to properly cleanse the toxins in the body, or regulate the acid concentration, and maintain water balance. This can significantly increase the risk for kidney infection, and therefore, our risk for kidney damage or failure.

In the new study, published in the American Journal of Kidney Diseases, Parikh and his colleagues recruited a total of 22 marathon runners with an avaerage age of 44, in the Hartford Marathon to give their blood and urine before and after the race to look for evidence of kidney injury. They were looking for those who were running distances longer than 13 miles for at least five years, who hadn't completed a marathon in the last four weeks, and were planning to run one in the near future. They specifically focused on damaged and dead cells in the urine that had washed out after acute injury to the kidney's tubules. Proteins in urine that signaled inflammation — NGAL and interleukins — were also measured. Physical stress lead to a five to 10 times increase from normal.

Woman running Researchers at Yale find marathon running can lead to short-term acute kidney injury. Photo courtesy of Pixabay, Public Domain

The findings revealed over 80 percent of the runners showed signs of stage 1 acute kidney injury after the race. During this stage, one of the following occurs — either a rise in serum creatinine of 26 millimoles per liter (μmol/L) or greater within 48 hours; 50 percent or greater increase in serum creatinine (1.5 fold from baseline) within the preceding seven days; or a fall in urine output to less than 0.5 mL/kg/hour for more than six hours. However, this was only short-term; most of the runners' kidneys returned to normal within 24 to 48 hours.

Although the runners recovered, it's not known if short-term kidney injury can lead to cumulative damage, or if some people do not recover in the short-term. It's not clear whether running a marathon directly leads to short-term kidney damage. A number of aspects of running could damage the kidneys, such as less blood flow to the kidneys, high core body temperature, and dehydration.   

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Parikh does caution people who are at-risk for kidney disease, such as those with diabetes, high blood pressure, or who are older, should reevaluate if marathon running is safe of them. This short-term study warrants further investigation on whether marathoning is linked with any permanent kidney damage.

"Research has shown there are also changes in heart function associated with marathon running. Our study adds to the story -- even the kidney responds to marathon-related stress," said Parikh.

Like with everything else in life, running should be done in moderation, and catered to our own health.

Source: Mansour SG, Verma G, Pata RW et al. Kidney Injury and Repair Biomarkers in Marathon Runners. American Journal of Kidney Diseases. 2017.

See Also:

Eating Red Meat Linked To Kidney Failure Risk

Growing Kidneys In The Lab May End Transplant Waitlist

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