Last reviewed: 11 May 2026
The oldest artificial sweetener (1879). Used in UK table-top blends, soft drinks and toothpaste.
E954 appears as "saccharin", "sodium saccharin" or "calcium saccharin". Discovered in 1879; 300–500 times sweeter than sugar; zero calories. The 1970s rat-bladder-tumour finding that prompted health warnings was later traced to a mechanism specific to male rat urine chemistry — IARC removed saccharin from its carcinogen list in 1999. The remaining ongoing questions concern gut bacteria and glucose tolerance, where the data are unsettled.
In the 1970s, high-dose feeding studies in male rats produced bladder tumours, prompting warning labels in the US and a long-running ban in Canada. Subsequent mechanistic work showed the tumours depended on rat-specific urine chemistry — high protein content plus mineral concentrations that allowed insoluble crystals to form in the bladder, causing chronic irritation. Humans don't share this urine profile.
By the late 1990s, large human cohort studies had found no bladder-cancer signal even at high lifetime saccharin intake. The IARC removed saccharin from its carcinogen list in 1999; the US NTP followed in 2000, and Congress lifted the warning-label requirement that same year. Canada lifted its ban in 2014. This is one of the cleaner cases of a cancer signal that was followed up, explained mechanistically, and shown not to apply to humans.
E954 is saccharin — discovered accidentally in 1879 at Johns Hopkins University, making it the world's oldest synthetic sweetener.
The 1970s tumour finding has been reviewed at length. Male rats fed high-dose sodium saccharin develop bladder tumours via formation of insoluble silicate-protein crystals in the urine. Female rats are largely unaffected; mice are unaffected; humans don't share the urine chemistry. Large human cohort studies — including studies of long-term diabetic populations and lifetime users — have not found a bladder-cancer signal. The IARC delisted saccharin in 1999.
Animal and small human studies (notably an Israeli 2014 trial) reported that saccharin shifted gut microbial composition and impaired glucose tolerance in a subset of participants. Larger and more recent studies have produced mixed results. The signal is real in some experiments and absent in others; the dose, baseline microbiome and exposure duration all appear to matter. The clinical relevance for typical UK intakes — a few sweetener tablets a day in a coffee — is not established.
Saccharin is a sulfonamide. People with documented sulfonamide drug allergy are sometimes advised to avoid it, though clinical cross-reactivity is rare and the evidence is largely case-reports. Genuine saccharin allergy is very rare.
Saccharin crosses the placenta and clears slowly from foetal tissues — an older finding that prompted historical advice to limit intake in pregnancy. Current EFSA opinion is that the ADI covers pregnant women; UK NHS guidance is that intakes within the ADI are not a concern.
UK/EU: Approved (E954). ADI 5mg/kg body weight per day (EFSA).
US: FDA approved. Removed from the NTP carcinogen list in 2000; warning-label requirement repealed the same year.
IARC: Group 3 — "not classifiable as to its carcinogenicity to humans" (delisted from Group 2B in 1999).
Canada: Approved since 2014 (banned in food 1977–2014, table-top use permitted throughout).
Look for "saccharin", "sodium saccharin", "calcium saccharin" or E954. The most likely place is a table-top sweetener — particularly Sweet'N Low or Hermesetas. At the 5mg/kg ADI, a 70kg adult's daily limit is 350mg saccharin — equivalent to about 80 typical sweetener tablets. Everyday table-top use is well inside the limit.
Scan barcodes to see which sweeteners turn up in your food and how often E954 appears across your week.
Get NutraSafe on the App StoreLast updated: 11 May 2026
Free to log up to 25 foods/day · NutraSafe Pro £3.99/month for AI Coach, allergen warning detail and full reaction history.