Effects of lemon-tomato juice consumption on crystal formation in the urine of patients with calcium oxalate stones: A randomized crossover clinical trial.

Background: Dietary supplementation with citrate-containing juices may serve as an effective alternative to potassium citrate therapy for preventing calcium oxalate stone recurrence. This study was performed to evaluate whether consumption of lemon-tomato juice can decrease the tendency for stone formation in the urine of calcium oxalate stone formers.

Materials and methods: The study was conducted as a prospective interventional randomized crossover clinical trial with a repeated-measures design. Twenty-two patients with calcium oxalate stones and no metabolic abnormalities in the urine treated with lithotripsy at a tertiary care center from August 2017 to July 2018 were recruited. After a 14-hour overnight fasting, urine samples were collected after the patients consumed either milk only or milk and lemon-tomato juice. Their urine was tested for multiple parameters, including urine pH, specific gravity, calcium-creatinine ratio, and supersaturation with sodium oxalate, followed by optical density measurement via spectrophotometry.

Results: There were no significant differences in the background characteristics between the 2 groups. The optical density of the urine samples obtained after consumption of milk only was significantly higher than that after consumption of milk and lemon-tomato juice (mean = 0.131 for milk only vs. 0.053 for milk and lemon-tomato juice, p < 0.001). The urine calcium-creatinine ratio was similar between the groups (mean = 0.141 for milk only vs. 0.076 for milk and lemon-tomato juice, p = 0.019).

Conclusions: The addition of lemon-tomato juice as a source of citrate in the diet significantly decreases the established risk factors for calcium oxalate stone formation in patients. This study was prospectively registered at CTRI under number CTRI/2017/04/008312 on April 7, 2017.