The formation of various types of stones in the urinary tract is strongly influenced by urinary pH. An acidic urinary pH promotes the crystallization of uric acid and cystine, respectively. Moreover, changes in systemic acid-base homeostasis alter urinary excretion of citrate, an important inhibitor of calcium oxalate stone formation. The effect of beverages on urinary pH and citrate excretion is mainly determined by the presence of bicarbonate and citrate. The bicarbonate content of mineral water can replace alkalization therapy with potassium citrate and contribute to urine inhibitory power by increasing urinary pH and citrate excretion. Citrus juices are rich sources of citrate. Oral citrate is absorbed in the intestine and nearly completely metabolized to bicarbonate, providing an alkali load, which in turn increases urinary pH and citrate excretion. However, data from observational and interventional studies on the effect of different types of citrus juices on the risk of urinary stone formation are conflicting. In conclusion, favourable changes in urinary pH and citrate excretion can be attained by various beverages. However, the long-term efficacy of certain beverages for the recurrence prevention of different types of stones has yet to be determined.
Keywords: Bicarbonate; Calcium oxalate; Cystine; Uric acid; Urinary pH; Urinary stones.