Findings: Dietary Risk Factors for Kidney Stone Recurrence

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A diet higher in calcium and potassium intake may help to reduce the risk of recurrent kidney stones, concludes a study in Mayo Clinic Proceedings.

The prospective study included 411 patients with their first episode of symptomatic kidney stones, with obstruction confirmed by imaging or stone passage, along with 384 stone-free controls. Both groups completed an electronic food frequency questionnaire during a baseline study visit. Dietary risk factors were compared between groups. Dietary associations with validated symptomatic recurrence were analyzed in proportional hazards models, with adjustment for fluid and energy intake and for nondietary risk factors.

Baseline characteristics associated with incident kidney stone formation included older age, White race, higher body mass index (BMI), lower educational level, more hypertension, history of working in hot temperatures, and history of urinary tract infection and chronic diarrhea. During a median follow-up of 4.1 years, 17.8% of patients had recurrent symptomatic kidney stones. Clinical factors associated with recurrence included higher BMI; retained, asymptomatic stones of computed tomography; and higher scores on the Recurrence of Kidney Stone prediction tool.

Kidney stone risk was higher for individuals with dietary calcium intake of less than 1200 mg/day and higher for those with fluid intake of less than 3400 mL/day. On adjusted analysis, recurrent stone risk was associated with lower calcium, potassium, caffeine, and phytate intake, as well as lower total fluid intake. Lower dietary calcium remained a significant predictor on analysis, including further adjustment. Dietary potassium was significant only among patients not using thiazide diuretics or calcium supplements.

Several studies have reported on dietary factors associated with incident kidney stones, but little is known about dietary factors that may increase the risk of recurrent stones. “Enriching diets in stone formers with foods high in calcium and potassium may help prevent recurrent symptomatic kidney stones,” according to the authors. Although patients are not likely to change their diet to prevent initial kidney stones, the researchers add, “[they] may be eager to do so to prevent symptomatic recurrence” [Chewcharat A, et al. Dietary risk factors for incident and recurrent symptomatic kidney stones. Mayo Clin Proc 2022; 97:1437–1448. doi: 10.1016/j.mayocp.2022.04.016].