During the hot summer months, news outlets and healthcare workers often remind the public to avoid prolonged periods outdoors and to stay well-hydrated. This is clearly important to our overall health, but how does heat specifically affect our kidneys? Discover what researchers have learned about the changes in kidney function when tested under different heat conditions, and what can cause kidneys to tap into their GFR reserves.* 

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What is eGFR reserve?

Normal functioning kidneys have the ability to increase their function in times of need. This ability to hold a reserve of untapped kidney function is called the glomerular filtration rate (GFR) reserve. Researchers study GFR reserves by tracking levels of creatinine, a waste product formed after eating a high-protein meal. 

What researchers did

In a recent study, researchers recruited 16 healthy adult participants to monitor under two different heat conditions – normal heat conditions, and mild heat stress. After retrieving baseline readings, they gave each participant a whey protein shake and monitored their kidney function for two and a half hours. 

What they found

They found that participants had an increase in creatinine levels after drinking the shake under normal heat conditions but not under mild heat stress. With the observations in creatinine from each heat condition, researchers learned that the kidneys did not increase their function, or GFR, to the same degree when faced with mild heat stress as they did at normal temperatures. 

What it means

The findings indicate that kidneys likely use GFR reserve to maintain a lower degree of function, say the authors, adding that they explain why people at greater risk for kidney damage during heat waves also generally belong to groups—such as older adults—that are known to already have reduced GFR reserves. 

*Heat stress prompts kidneys to tap into their reserves. (2022, September 23). Medical Xpress. Retrieved December 4, 2022, from https://medicalxpress.com/news/2022-09-stress-prompts-kidneys-reserves.html