Effect of Diet on the Tendency for Stone Formation in Patients with Calcium Oxalate Stones in the Urinary Tract

Patients with idiopathic calcium oxalate stones should follow a low-oxalate diet to avoid recurrence. The goal of this study on patients with calcium oxalate stones was to investigate the impact of dietary calcium content on the formation of calcium oxalate crystals in urine using an in vitro supersaturation study of fresh postprandial urine samples and to observe the morphology of the crystals formed using polarized optical microscopy. The study was designed as a prospective interventional randomized crossover clinical trial with repeated measures. Sixty patients with calcium oxalate stones and no metabolic abnormalities in urine were treated with lithotripsy at a tertiary care center from May 2016 to May 2019. Following a 14-hour overnight fast, urine samples were collected after the patient was given either a low or high-calcium meal for breakfast, followed by a high-oxalate meal four hours later.

The optical density values and calcium-creatinine ratio of urine samples obtained following a high calcium meal are significantly higher than those obtained following a low calcium meal (p<0.001). These discoveries were reflected in the size, shape, and number of formed crystals. During a supersaturation study of postprandial urine samples following a high-oxalate diet, no crystals were formed when urine calcium levels were low. Kidney stone production is substantially influenced by a high calcium intake in the diet. Even when consuming a high-oxalate diet, a low-calcium meal has a lower risk of causing kidney stones.