Health agencies have made two separate assessments of aspartame. In 2023 the International Agency for Research on Cancer (part of the World Health Organization) classed it as "possibly carcinogenic" (Group 2B), because there was limited evidence about liver cancer that could have been due to chance or other factors [1, 2]. At the same time, the WHO expert committee on food additives did not find the evidence linking aspartame with cancer convincing and kept the acceptable daily intake unchanged: 40 mg per kilogram of body weight, which means a 70 kg adult would need to drink more than 9 to 14 cans of diet soft drink a day to exceed it [2]. Research on aspartame continues [2].
Key points
- "Possibly carcinogenic" means the evidence is limited; this classification does not show how much risk there is at usual levels of intake [2].
- The acceptable daily intake was not changed: 40 mg per kilogram of body weight [2, 3].
- Saccharin was once a concern because of bladder cancer in rats, but it was later shown that this mechanism does not occur in humans [4].
- The World Health Organization does not recommend sweeteners for weight loss and suggests getting used to less sweet tastes overall [7].
What is aspartame and where is it found?
Aspartame is an artificial sweetener about 200 times sweeter than sugar, used since the 1980s in diet drinks, chewing gum, gelatin desserts, ice cream, yoghurt, breakfast cereals, toothpaste and some medicines such as cough lozenges and chewable vitamins [2, 5]. In the gut, aspartame is completely broken down into three substances (phenylalanine, aspartic acid and methanol) that are also released from ordinary foods; aspartame itself does not enter the bloodstream [3].
What does "possibly carcinogenic" mean?
The International Agency for Research on Cancer assesses whether a substance can cause cancer and how strong the evidence is; this assessment does not say at what amount, or how much, risk there is [2]. Group 2B is the third of four levels and is generally used when the evidence in humans is limited and not yet convincing [2].
For aspartame, there were only three studies of diet drinks that allowed liver cancer to be examined; all three saw a link (in everyone or in certain groups), but it could have been due to chance or other factors [3]. The evidence from animal studies was also rated "limited" because of problems with how the studies were designed and reported [3].
The WHO expert committee on food additives, which assesses risk at real levels of intake, concluded at the same time that the evidence linking aspartame with cancer in humans is not convincing, and kept the acceptable daily intake unchanged [2, 3]. The US Food and Drug Administration also said it disagrees with the agency's classification, because it considers the studies the agency relied on to have significant shortcomings [4, 5]. Both international bodies have said that more and better studies are needed [2].
How much aspartame a day is acceptable?
The "acceptable daily intake" is the amount that can be consumed every day over a lifetime and is considered safe for health [5]. For aspartame it is 40 mg per kilogram of body weight [2]; the US Food and Drug Administration has set 50 mg [5].
- An adult weighing 70 kg: a can of diet soft drink contains 200 to 300 mg of aspartame, so they would need to drink more than 9 to 14 cans a day, with no aspartame from other sources, to exceed the acceptable intake [2].
- Children: because the limit is based on body weight, it is proportionally lower for a child, who weighs less [2].
- Phenylketonuria (PKU): people with this rare inherited condition, whose bodies cannot break down phenylalanine, should avoid or strictly limit aspartame; the labels of these products state that they contain phenylalanine [5].
What did the large French study show?
In a study of more than 100,000 French adults followed for about 8 years, those who consumed more artificial sweeteners developed cancer slightly more often; this link was seen for aspartame and acesulfame potassium, but not for sucralose [6, 4]. This type of study looks at people's habits and cannot on its own prove that the sweetener was the cause; people who consume more sweeteners may also differ in other ways [4, 6].
Other studies have not all found the same; for example, in a large American study, drinks containing aspartame were not linked to lymphoma, leukaemia or brain cancer [4]. For this reason, experts consider more studies with longer follow-up necessary [2].
Saccharin, sucralose and other sweeteners
| Sweetener | What studies have shown |
|---|---|
| Saccharin | Large amounts caused bladder cancer in rats; it was later shown that this mechanism does not occur in humans, and in 2000 it was removed from the US list of carcinogens; human studies have not shown a clear link with bladder cancer either [4] |
| Cyclamate | Banned in the United States in 1969 because of animal studies; later reviews concluded that it does not cause cancer, and it is permitted in many other countries [4] |
| Sucralose | Various studies have found no evidence that it causes cancer in humans [4]; a 2023 laboratory study raised questions about a substance formed during its manufacture (sucralose-6-acetate) that have not yet been studied in humans [8] |
| Acesulfame potassium | Linked to slightly more cancer only in the French study; there are no other human studies of it [4, 6] |
| Stevia | A sweetener of plant origin; the World Health Organization's advice not to use sweeteners for weight control also covers stevia [7] |
What should I do? Cut down on sweetness overall
According to the World Health Organization, the safety of aspartame is not a major concern at the amounts commonly consumed [2]. Even so, sweeteners have no nutritional value, and the World Health Organization advises not using them to lose weight; it is better to reduce the sweetness of food and drinks overall and choose unsweetened drinks or fruit instead [7]. This advice does not apply to people with diabetes, who should talk to their doctor [7]. See Does sugar make cancer grow?
Frequently asked questions
Is a diet soft drink better than a regular one?
In a French study, sugary drinks were linked to slightly more cancer and diet drinks were not [9]; but a later analysis of the same group, which counted sweeteners from all foods and drinks, linked them to slightly more cancer [6]. The World Health Organization does not recommend sweeteners for weight control and suggests unsweetened drinks such as water [7].
What about sugar-free chewing gum or toothpaste with sweeteners?
What should people with diabetes do?
Do sweeteners help with weight loss?
Study results have not all agreed [4]. A review carried out for the World Health Organization found no long-term benefit for reducing body fat and linked long-term use with a possibly higher risk of type 2 diabetes and heart disease; these links may, however, be explained by other characteristics of the people studied [7].
Why do the agencies disagree?
The International Agency for Research on Cancer only assesses whether a substance can cause cancer; the expert committee on food additives assesses how likely harm is at real levels of intake [2]. The US Food and Drug Administration also considers the studies behind the classification to have shortcomings [5].
Notes for doctors (for physicians)
For physicians
IARC (Monograph 134, June 2023). 25 experts from 12 countries. Group 2B on limited evidence in humans for hepatocellular carcinoma (three studies of artificially sweetened beverages as a proxy for aspartame exposure; positive association overall or in important subgroups, with chance, bias or confounding not ruled out), limited evidence in animals (increased tumours in mice and rats of both sexes in three published studies, with concerns about design, interpretation and reporting) and limited mechanistic evidence (induction of oxidative stress in experimental systems) [1, 3]. According to the NCI, of these three studies (four cohorts) one showed an association in the whole cohort and one in people with diabetes, and the third found none; a fourth study published after the IARC meeting also found no association [4].
JECFA (96th meeting). Complete hydrolysis in the gastrointestinal tract and no systemic exposure to aspartame; not considered genotoxic; of 12 oral carcinogenicity studies only those by Soffritti et al. (2005 to 2010) were positive, with limitations in design, conduct, reporting and interpretation; no consistent association with a specific cancer type (HCC, breast, non-Hodgkin lymphoma, multiple myeloma) was shown, and reverse causality, chance, bias and confounding could not be ruled out. ADI 0 to 40 mg/kg reaffirmed [3]. FDA: ADI 50 mg/kg and explicit disagreement with the IARC classification [5].
NutriNet-Santé (Debras, PLoS Med 2022). 102,865 adults, median follow-up 7.8 years, repeated 24-hour dietary records including brand names. Higher consumers (above the median) vs non-consumers: overall cancer HR 1.13 (1.03 to 1.25; 3,358 cases); aspartame 1.15 (1.03 to 1.28); acesulfame-K 1.13 (1.01 to 1.26); breast cancer with aspartame 1.22 (1.01 to 1.48; 979 cases); obesity-related cancers 1.13 (1.00 to 1.28) for total sweeteners and 1.15 (1.01 to 1.32) for aspartame. Limitations stated by the authors: selection bias, residual confounding and reverse causality [6]. Sucralose was not associated with cancer in this cohort [4].
Sucralose-6-acetate. Schiffman 2023 (in vitro assays only): this intermediate and impurity of sucralose manufacture (up to 0.67% in commercial samples) was genotoxic (clastogenic) in the MultiFlow assay and the micronucleus test; no human data [8].
WHO guideline (2023; conditional recommendation). Do not use non-sugar sweeteners for weight control or to reduce the risk of noncommunicable diseases, except in people with diabetes; the recommendation is conditional because the evidence may be confounded [7].
References
9 referencesShow all references, 1 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9Sugary drink consumption and risk of cancer: results from NutriNet-Santé prospective cohort
This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
Printed from the website; the full and up-to-date version: https://drdabiri.com/en/questions/aspartame-artificial-sweeteners-cancer/