To the Editor.—
In a recent letter to the editor, the issue was again raised of whether or not ascorbic acid lowers urinary pH.1 There are reports that ascorbate does2-6 and reports that it does not7-9 change urine acidity. These contradictory results arise from a difference in (1) selection of patients and (2) semantics. The studies that evaluated subjects with urinary tract infection showed a decrease in the pH of voided urine; studies using subjects without infection showed no change. The inhibition of bacterial urease10-13 is undoubtedly the cause of change, when it occurs. The ascorbic acid effect is more accurately described as preventing the alkalinization of urine rather than producing an acid urine. This occurs by preventing or decreasing ammonia production by bacterial urease. This is illustrated by an experiment in which urea, urease, and ascorbic acid were put into 0.1M phosphate buffer. In the
Axelrod DR. Ascorbic Acid and Urinary pH. JAMA. 1985;254(10):1310–1311. doi:10.1001/jama.1985.03360100058010
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