Even light exercise can cut women’s chance of developing a kidney stone by one-third, according to a large study from the University of Washington School of Medicine in Seattle.
Dr. Mathew Sorensen led the study whose findings will be discussed Friday at the American Urological Association conference in San Diego.
In the last 17 years, the incidence of kidney stones has risen by 70 percent—most rapidly among women. Approximately 9 percent of people will have a kidney stone at some point in their life.
Obesity and calcium supplements—which many women take after menopause—raise the risk of developing a kidney stone. In fact, a government task force recently advised healthy older women to avoid the supplements, as low-dose pills won’t do much to keep bones strong, but can make kidney stones more likely.
The researchers' findings were based on statistics from 85,000 women aged 50 and older in the government-funded Women’s Health Initiative study. At the beginning of the study, each woman had an exam to log her weight, height and body mass index. Participants also filled out annual surveys about what they ate. Researchers considered factors such as drinking a lot of fluids or eating less salt and meat when looking potential risks for kidney stones.
To track activity, participants logged their exercise and researchers translated the numbers into “METs”—a measure of the amount of effort an activity requires. For instance, 10 METs per week is roughly equivalent to two and a half hours of walking at a moderate pace or one hour of jogging.
After close to eight years, three percent of participants had developed a kidney stone. Compared to women who had no exercise, those with up to 5 METs each week were 16 percent less likely to have a kidney stone. As the amount of exercise increased, the chance for kidney stones continued to go down. Participants with 5 to 10 METs had a 22 percent lower risk and women with 10 METs or more were 31 percent less likely to have kidney stones than woman who did not exercise. Beyond 10 METs, there was no additional benefit. Furthermore, the intensity of exercise did not matter.
Exercise may help by changing the way the body handles nutrients and fluids that cause stone formation. Those who exercise sweat out salt and tend to retain calcium in their bones. Those who do not exercise may have calcium and salt build up in the kidneys. Active people also tend to drink water and fluids after exercise. Staying hydrated also cuts down your risk. Finally, exercise also decreases the chance of heart disease, diabetes, high blood pressure and other conditions that raise the risk of kidney stones.