To compare dietary factors between incident symptomatic stone formers and controls, and between the incident stone formers, to determine whether dietary factors were predictive of symptomatic recurrence.
Patients and methods
We prospectively recruited 411 local renal stoners (medical record validated) and 384 controls seen at the Mayo Clinic in Minnesota or Florida between January 1, 2009 and August 31, 2018. Dietary factors were based on a Viocare, Inc, food frequency questionnaire administered during a personal study visit at baseline. Logistic regression compared dietary risk factors between incident symptomatic stone formers and controls. Incident stone formers were followed up for validated symptomatic recurrence in the medical record. Cox proportional hazard models estimate the risk of symptomatic recurrence with dietary factors. Analyzes adjusted for fluid intake, energy intake and non-diet risk factors.
In fully adjusted analyses, lower dietary calcium, potassium, caffeine, phytate, and fluid intake were all associated with a greater likelihood of an occasional symptomatic kidney stone. Of the incident stone formers, 73 experienced symptomatic recurrence during a median follow-up of 4.1 years. Adjustment for body mass index, fluid and energy intake, lower dietary calcium intake and lower potassium intake were predictive of symptomatic recurrence of kidney stones. With further adjustment for non-dietary risk factors, lower dietary calcium intake remained a predictor of recurrence, but lower potassium intake only remained a predictor of recurrence in those not taking thiazide diuretics or calcium supplements.
Enriching stone-former diets with foods high in calcium and potassium can help prevent recurrent symptomatic kidney stones.