Is the "Pandemic Diet" Nonlithogenic?

The COVID-19 pandemic and worldwide quarantine resulted in major changes in individual lifestyles. In New York State, March 16, 2020, marked the end of in-restaurant dining and a reported shift to more cooking at home. We investigated the 24-hour urine of patients with known history of nephrolithiasis to see if changes during COVID-19 pandemic altered the risk of stone disease. Retrospectively, patients with history of nephrolithiasis seen for an outpatient visit from April 1, 2020, to December 31, 2020, were studied. All patients had a 24-hour urine study "pre-COVID" defined as before March 16, 2020, "during-COVID" from March 16, 2020, to December 31, 2020; if available, "post-COVID" from January 1, 2021, to October 31, 2022, was also included. Mean study values were compared using paired, two-tailed t-tests. Ninety-three patients (M = 54, F = 39) with a mean age of 60 years were evaluated. Twenty-four-hour urine revealed a significant reduction in urinary sodium (uNa) levels from pre-COVID (166.15 ± 7.51 mEq/L) compared with during-COVID (149.09 ± 7.55 mEq/L) (p = 0.015) and urinary calcium (uCa) levels from pre-COVID (214.18 ± 13.05 mg) compared with during-COVID (191.48 ± 13.03 mg) (p = 0.010). Post-COVID 24-hour urine (N = 73) levels for uNa (138.55 ± 6.83 mEq/L, p = 0.0035) and uCa (185.33 ± 12.61 mg, p = 0.012) remained significantly reduced compared with pre-COVID values, but with no difference compared with during-COVID values. Upon age stratification, this significance was found only in patients younger than 65. There were no significant differences in 24-hour urine total volume, magnesium, or citrate levels. During the COVID-19 lockdown, dietary choices limited to home-cooked meals allowed patients to better identify their food choices. This study demonstrates that home-cooked meals improved urinary parameters minimizing lithogenic risk factors for stone formation, including hypernatriuria and hypercalciuria. That these changes persisted into the post-COVID period may indicate improved dietary practices after the lockdown ended.