LONG-TERM FEEDING OF SODIUM SACCHARIN TO NONHUMAN-PRIMATES - IMPLICATIONS FOR URINARY-TRACT CANCER

Background: It was observed in the early 1970s that saccharin produced bladder cancer in rats, However, it has been unclear whether sodium s accharin when consumed by humans poses a substantial carcinogenic haza rd, Numerous epidemiologic studies have not shown any evidence of incr eased urothelial proliferation associated with ingestion of sodium sac charin, Purpose: Our purpose was to determine the effects of long-term feeding of sodium saccharin to three species of nonhuman primates, Me thods: Twenty monkeys of three species (six African green, seven rhesu s, six cynomolgus, and one hybrid [of rhesus male and cynomolgus femal e parentage]) were treated with sodium saccharin (25 mg in the diet/kg body weight daily for 5 days a week) beginning within 24 hours after birth and continuing for up to 24 years, Sixteen monkeys (seven rhesus and nine cynomolgus) served as controls, During their last 2 years of life, urine was collected from selected treated and control animals a nd evaluated for various urinary chemistries and for the presence of c alculi, microcrystalluria, and precipitate, Urinary bladders were exam ined by light microscopy and by scanning electron microscopy, Results: Sodium saccharin treatment had no effect on the urine or urothelium i n any of these monkeys, There was no evidence of increased urothelial cell proliferation, and there was no evidence of formation of solid ma terial in the urine, Conclusion: Although the dose of sodium saccharin administered to these monkeys was only five to 10 times the allowable daily intake for humans, the results provide additional evidence that sodium saccharin is without a carcinogenic effect on the primate urin ary tract.