Protecting Kidney Function
The Centers for Disease Control and Prevention states that more than 20 million U.S. citizens suffer from chronic kidney disease—the slow loss of kidney function—and that it is the ninth leading cause of death. Recently, researchers learned that exercise may slow kidney function decline in kidney disease patients.
Published in the Journal of the American Society of Nephrology (2013; doi: 10.1681/ASN.2013040392), the study included 256 kidney disease patients 
from the Seattle Kidney Study. Each participant completed a “Four-Week Physical Activity Questionnaire,” and results were compared with kidney function for a mean follow-up time of 3.7 years. In analyzing the data, researchers discovered that individuals who engaged in at least 150 minutes of physical activity per week showed a significant reduction in kidney function decline. Scientists also found that “each 60-minute increment in weekly physical activity duration [was] associated with a 0.5% slower decline per year in [kidney function].”
Though physical activity was associated with reduced kidney function decline, the authors could not define a link between physical activity and prevention or reduction of end-stage kidney disease, which is complete or near-complete kidney failure.
Reducing The Risk Of Kidney Stones
Along with benefiting kidney function, regular exercise can help with another kidney-related malady: kidney stones.
A second study—also published in the Journal of the American Society of Nephrology (2013, doi: 10.1681/ASN.2013050548)—involved 84,225 postmenopausal participants in the Women’s Health Initiative Observational Study. Subjects had no previous history of nephrolithiasis, also known as kidney stones.
Researchers looked at physical activity levels, dietary intake and body mass index. Then they compared that information with kidney stone development.
According to the data, women who reported the lowest physical activity levels experienced a 16% decreased risk of kidney stones compared with inactive women. “As activity increased, the risk of incident stones continued to decline until plateauing at a decrease of approximately 31% for activity levels ≥10 METs/week,” the authors explained. There was no correlation between exercise intensity and kidney stone development.
As dietary intake increased, kidney stone risk rose by as much as 42%. Kidney stones were also more prevalent among subjects with a higher BMI.
“In summary, physical activity may reduce the risk of incident kidney stones in postmenopausal women independent of caloric intake and BMI, primarily because of the amount of activity rather than exercise intensity,” concluded the authors. “Higher caloric intake further increases the risk of incident stones.”