The Association Between Fasting and Risk of Urine Salts Supersaturation and Stone Formation: A Fact or Fiction

Background: Urinary stones are a common urological problem. Regular prolonged fasting is a known habit and involved abstinence from food and water for several hours. The continuous concern is about the effect of fasting on the risk of stone formation. The purpose of the study was to investigate the risk of fasting on supersaturation of urine.
Methods: This study was conducted after one month of daily fasting of 15 hours on a cohort of healthy people in the year 2022 aiming at evaluating urinary salts. A total number of 35 patients were included in the study. Urine samples were tested for the concentration of different solutes. The urine flow rate was tested. The test was done in fasting and non- fasting states. The results of the study were expressed as mean ± standard deviation.
Results: Six (16.6%) patients only had a history of acute severe renal colic. The mean urinary excretion of creatinine decreased from 9.1 ± 0.6 to 8.2 ± 0.9 µmol / min in the fasting state. There was a significant reduction in the mean urinary excretion and urinary concentration of calcium (from 3.4 ± 0.6 to 0.9 ± 0.1 µmol / min; p < 0.05 and from 3.8 ± 0.5 to 1.8 ± 0.56 mmol /l; p < 0.05 respectively.
Conclusions: Fasting doesn’t cause urinary supersaturation by calcium and sodium salts and this will not increase the risk for urinary stone formation. There was no increased risk of admission to emergency rooms due to renal colic.