Effect of vitamin C on endogenous formation of N-nitrosamines in ureterosigmoidostomy patients.

The bacterially catalyzed formation of nitrosamines in the rectosigmoid is a favorite theroy for the increased risk of colon carcinomas following ureterosigmoidostomy. The urine/feces mixtures of 20 ureterosigmoidostomy patients were analyzed for nitrate, nitrite, volatile and nonvolatile nitrosamines prior to, and after, oral administration of vitamin C, a known nitrosation inhibitor. Following a 4-week period of daily ingestion of 2 g vitamin C (1 g in children) there was a slight, but not significant, decrease of volatile and nonvolatile nitrosamines and nitrite, as well as a nonsignificant increase in nitrate in the urine/feces of these patients. No correlation between the vitamin C concentration in serum or urine/feces mixture and the nitrosamine excretion was observed. These results suggest that the administration of vitamin C is not a suitable method for prophylaxis of endogenous nitrosation in ureterosigmoidostomy patients. Clinical and experimental findings implicate that factors other than nitrosamines play an important role in colon carcinogenesis of patients with ureterosigmoidostomies or other forms of urinary diversions using the small or large bowel.