Saccharin

Saccharin is a benzoic sulfimide and the oldest synthetic sweetener, discovered in 1879 and coded E 954 in the EU. It is roughly 300 to 500 times sweeter than table sugar, contributes no energy, and passes through the body largely unchanged. At higher concentrations it leaves a metallic aftertaste, so it is usually blended with cyclamate or aspartame. EFSA re-evaluated saccharin in November 2024 and raised the ADI from 5 to 9 mg per kilogram of body weight per day, expressed as the free imide. The FDA uses 15 mg/kg. Estimated EU exposure sits below the new figure. The increase closed a long chapter. Rats fed high doses of sodium saccharin developed bladder tumours, and saccharin was listed as a suspected human carcinogen in the United States. Whysner and Williams set out the mechanism: at those doses rat urine forms a precipitate that damages the bladder lining and drives compensatory cell division. Human urine does not behave this way. The US National Toxicology Program delisted saccharin in 2000, and human studies have found no bladder cancer link. The open question is no longer cancer. It is whether long-term use alters the gut microbiome and glucose handling, where human trials remain small and inconsistent.

Last reviewed: August 25, 2026

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