Yes, sodium or calcium saccharin has been used in studies with rats, and it has been found to increase the incidence of bladder tumors in these animals. This carcinogenic effect was discovered in early studies conducted in the 1970s, where rats fed high doses of saccharin showed an increased incidence of bladder cancer. However, it is important to note that these effects may not directly translate to humans, as the metabolism and biological responses to substances can vary between different species.
