as well as their symptomatic recurrence, a population-based study of dietary factors shows.
“Our research is of particular importance as recommendations for preventing symptomatic recurrence of kidney stones has largely been based on dietary factors associated with the incidence rather than the recurrence of stone formation,” Api Chewcharat, MD, Mayo Clinic, Rochester, Minn., said in a video discussing the study.
“We recommend a daily intake of calcium of approximately 1,200 mg and a diet that is high in potassium, especially high in fruits and vegetables, in order to prevent both incident and recurrent symptomatic kidney stone formation,” he stressed.
The study was published online in Mayo Clinic Proceedings.
Lower dietary calcium, potassium, and fluid associated with increased incidence
Some 411 patients with incident symptomatic kidney stone formation were recruited. Diets were compared between them and 384 controls. Patients were seen at the Mayo Clinic in either Minnesota or Florida between Jan. 1, 2009, and Aug. 31, 2018. “Dietary factors were based on a Viocare food frequency questionnaire administered during a baseline in-person study visit,” Dr. Chewcharat and colleagues observed.
During a median follow-up of 4.1 years, 73 patients experienced a symptomatic recurrence. In a fully adjusted analysis, a dietary calcium intake less than 1,200 mg/d was associated with incident stone formation. Similarly, among participants with a fluid intake less than 3,400 mL/d – about nine 12-oz glasses of fluid – was also associated with incident stone formation, as was a lower intake of dietary potassium, caffeine, and phytate. Phytate is an antioxidant found in whole grains, nuts, and other foods that can increase calcium absorption and urinary calcium excretion.
After excluding patients who were taking either a thiazide diuretic or a calcium supplement, lower dietary calcium and potassium, fluid, and phytate intake remained significantly associated with incident stone formation.
However, only lower dietary calcium intake was associated with a higher risk for symptomatic recurrence, although a lower dietary potassium intake was also associated with a higher risk for symptomatic recurrence in an analysis that adjusted for body mass index, fluid, and energy intake.
As the authors suggested, patients may be less keen to adjust their diet to prevent the development of incident kidney stones. On the other hand, they may be much more willing to adjust their diet to prevent their symptomatic recurrence. The Department of Agriculture currently recommends that individuals get approximately 1,200 mg/d of dietary calcium which, given the study results, appears to be justified for the prevention of symptomatic stone recurrence.
A higher-calcium diet is associated with a higher urinary pH, and citrate confers an alkali load which helps protect against the formation of calcium oxalate stones. Foods that are high in potassium also contain more fluid, citrate, and phytate, which, again, have been reported to be protective against kidney stones. “Changing your diet to prevent kidney stones can be very difficult,” Andrew Rule, MD, a nephrologist at the Mayo Clinic said in a statement.
“Thus, knowing the dietary factors that are most important for preventing kidney stone recurrence can help patients and providers know what to prioritize,” he added.
The authors have no conflicts of interest to declare.
A version of this article first appeared on Medscape.com.