Saccharin

What It Is

Saccharin is a high-intensity sweetener. FDA puts it at 200 to 700 times sweeter than table sugar. That wide range is FDA’s own figure, and we do not narrow it to a single number. Saccharin contains no calories: the body does not use it as an energy source, and US regulations call it a “non-nutritive sweetening agent”. In the EU it is E 954, which covers saccharin and its sodium, potassium and calcium salts.

Saccharin is the one sweetener on this site whose cancer scare has run its full course. It was labelled a suspected carcinogen in the 1970s, carried a warning by Act of Congress, and was then formally cleared by the same US body that had listed it. That history is the main reason to read this page. A newer question, about one manufacturing process, is still open.

The Cancer Question, and How It Closed

In the 1970s, rat feeding studies found more bladder tumours in male rats fed diets with more than 1% saccharin. Increases in female rats were not statistically significant, and the mouse data were inconsistent. IARC and the US National Toxicology Program (NTP) both listed saccharin as a suspected human carcinogen; NTP’s listing as “reasonably anticipated to be a human carcinogen” dates from 1981.

The Calorie Control Council then nominated saccharin for removal from NTP’s Report on Carcinogens. The review was not unanimous. NTP’s two internal review groups voted to delist it, 7 to 3 and 6 to 2. An advisory subcommittee recommended, 4 votes to 3, that it stay listed. Saccharin appeared in the 8th Report (1998) for the last time. The 9th Report, released on 15 May 2000, removed it.

NTP’s reasoning was specific. The bladder tumours in rats were tied to the rat’s own urinary system: urine pH, concentration and volume, the presence of a precipitate, and damage to the bladder lining, at dietary saccharin levels of 3% or more. In NTP’s words, these factors “would not be expected to occur in humans”, and several epidemiology studies showed “no clear association between saccharin consumption and urinary-bladder cancer.” FDA adds that more than 30 human studies found the rat results irrelevant to humans.

NTP did not claim more than that. It wrote that “it is impossible to conclude with absolute certainty that it poses no threat to human health”, and that sodium saccharin is “not reasonably anticipated to be a human carcinogen under conditions of general usage”. That is narrower than “saccharin does not cause cancer”, and it is what NTP actually concluded.

The Warning Label That Came and Went

The Saccharin Study and Labeling Act of 1977 (Public Law 95-203) required every saccharin product to carry the warning “THIS PRODUCT CONTAINS SACCHARIN WHICH HAS BEEN DETERMINED TO CAUSE CANCER IN LABORATORY ANIMALS.” The same Act blocked FDA from banning saccharin for 18 months, and Congress extended that moratorium seven times. The warning requirement was repealed in December 2000 (Public Law 106-554), seven months after NTP’s delisting, and California removed saccharin from its Proposition 65 list in April 2001.

The wording of the 1977 warning is reported identically by several independent sources, but we have not read it in the statute itself: the official scan of the law has no text layer.

Regulatory Status

In the US, saccharin is regulated at 21 CFR 180.37, which permits it as a sweetening agent in food. It is not a GRAS substance and it is not in Part 172 with aspartame and sucralose. Part 180 is for food additives permitted “on an interim basis pending additional study”, and the regulation still says its authority expires “when the Commissioner receives the final reports on the ongoing studies in Canada”. That 1970s wording was never rewritten after the 2000 delisting or the label repeal. Read literally, the regulation has not caught up with either.

In the EU, saccharin is authorised as E 954. EFSA re-evaluated it in a full opinion published on 15 November 2024, which did two new things:

• It raised the ADI from 5 to 9 mg/kg of body weight per day (expressed as free imide). The new figure is based on decreased body weight in animal studies, not the old rat bladder tumours. In people, EFSA found that a link between saccharin and weight gain “has not been convincingly demonstrated”.
• For the first time, it split its finding by manufacturing process. Saccharin made by the Remsen-Fahlberg process raised no genotoxicity concern from its impurities. For the Maumee process, “a concern for genotoxicity was identified for benzamide, while the genotoxic potential of 2-chlorobenzamide could not be fully assessed.”

The Maumee question is open. EFSA did not find that Maumee-process saccharin is unsafe; it found a concern it could not resolve. That is the next thing to watch for this sweetener.

The ADI: Whose Number?

• JECFA (the joint FAO/WHO expert committee): 9 mg/kg bw/day
• EFSA: 9 mg/kg bw/day, since 2024
• FDA: 15 mg/kg bw/day, from FDA’s “Safe Levels of Sweeteners” chart

Saccharin’s international figure has moved more than any other on this site. JECFA cut its ADI to a temporary 0 to 2.5 mg/kg in 1977, at the height of the cancer scare. The figure later settled at 5 mg/kg, which is what the EU used until EFSA’s 2024 opinion replaced it with 9. These historical figures come from JECFA’s evaluation records, which we have not yet re-read line by line. FDA’s chart gives its figure of 15 without showing how it was derived. Whichever number you use, name whose it is.

Calories, Carbohydrate and Blood Glucose

Pure saccharin contains no calories and no carbohydrate, and it does not raise blood glucose itself. It is used in milligram amounts and subtracts in full from net carbs.

What you buy is usually not pure saccharin. Tabletop packets are bulked with dextrose, which is ordinary, fast-digesting carbohydrate. If you are counting carbohydrate, count the carrier, not the saccharin. Nothing in our record shows a blood-sugar benefit from choosing saccharin over another high-intensity sweetener.

Comparison Note

Against aspartame: aspartame’s 2023 cancer classification has the same shape as saccharin’s 1970s one, but saccharin’s has closed and aspartame’s is still being watched. Against acesulfame potassium: neither is used by the body for energy, and both have an EU impurity question open. Against sucralose: sucralose is a full Part 172 food additive, while saccharin’s regulation is still formally interim.

For the bladder-cancer question, the record is about as complete as regulatory science gets. It is not the only safety question saccharin has raised, and EFSA’s 2024 opinion is the reason this page says so.