The physical stress of running a marathon can cause short-term kidney injury, according to research published in the American Journal of Kidney Diseases.
The researchers, from Yale in the US, studied a small group of runners who took part in the 2015 Hartford Marathon. They collected blood and urine samples before and after the event. They analysed several markers of kidney injury, including serum creatinine levels, kidney cells on microscopy, and protein levels in urine.
They found that 82 per cent of the runners studied showed stage 1 acute kidney injury soon after the race. The condition prevents kidneys from filtering waste from the blood.
Although the kidneys of the runners fully recovered within two days, the study authors say that the results raise questions about the long-term impact of marathon running. Although the sport is increasing in popularity globally, there has been a slight decrease in marathon running in Britain (of 5.47 per cent between 2009 and 2014).
The study’s lead author, Chirag Parikh, said: ‘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 hospitalised patients when the kidney is affected by medical and surgical complications.
‘We need to investigate this further. 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.’
There have long been anecdotal reports from distance runners about the impact of running marathons on their kidneys and I have seen a number of them in my surgery over the years with post-race blood in their urine which settles away after a few days and all investigations tend to be clear. This Yale-led study confirms that the physical stress of running a marathon can cause very short-term kidney injury, possibly due to a combination of dehydration, trauma or reduced kidney blood flow.
However, this was a very small study with limited clinical data available at all time points and larger studies are now needed to reproduce these findings. I also wonder what the point of the study was — it does not suggest we should stop endurance running or that marathons cause any long-term problems to the kidneys. The benefits of regular exercise would seem to far outweigh any potential risks such as this and so the usual advice about a healthy lifestyle remains unchanged.
Research score: 2/5