Effect of ascorbic acid on urine pH in patients with injured spinal cords

The ability of ascorbic acid to lower urinary pH in patients with spinal cord injury and neurogenic bladder was studied. Ascorbic acid (1 g four times daily) or placebo was administered for five days in a double-blind, crossover study to 20 patients with spinal cord injury and neurogenic bladder. Urine pH was measured for two days before and during administration of placebo or ascorbic acid. The mean decrease in urinary pH with ascorbic acid was 0.58, but this reduction was not statistically or clinically significant. Only 7 of 20 patients showed a mean urine pH of 5.5 or less (acidic) during treatment with ascorbic acid. The study suggests that an ascorbic acid dosage of 1 g four times daily should not be used to maintain an acidic urinary pH for control of urinary tract infections in patients with spinal cord injuries.