In July 2023, two WHO-linked agencies published different assessments of the same sweetener. IARC classified aspartame as “possibly carcinogenic to humans” (Group 2B). JECFA, on the same day, reaffirmed the acceptable daily intake of 0-40 mg/kg body weight.
Read badly, it sounds like a contradiction. Read carefully, it explains how scientific assessment works: identifying a possible hazard is not the same as estimating risk at real-life doses.
Hazard and risk are not the same thing
IARC evaluates hazard: can a substance cause an effect under some conditions? Group 2B means limited evidence in humans. It does not mean “it causes cancer if you consume it”. The same category contains very different exposures.
JECFA evaluates risk: how much can be consumed daily over a lifetime without appreciable risk, based on available data? That is why it kept the existing ADI: 0-40 mg/kg per day.
What 40 mg/kg means in practice
For a 70 kg adult, the theoretical threshold is about 2,800 mg per day. A can of diet drink usually contains much less, but amounts vary by product and market. The point is not to produce one universal count. The point is that dose matters.
For children, the margin is narrower because body weight is lower. For people who consume many diet drinks, chewing gums, light yogurts, supplements or tabletop sweeteners, the daily sum matters more than one serving.
EFSA and the European assessment
EFSA re-evaluated aspartame in 2013 and confirmed an ADI of 40 mg/kg body weight per day. The assessment covered toxicity, genotoxicity, carcinogenicity and metabolism. One warning remains essential: people with phenylketonuria must avoid or control aspartame because it contains phenylalanine.
For the general population, the debate is about exposure and margins. For people with phenylketonuria, the issue is specific and the label must say so.
How to read the label
Look for “aspartame”, “E951” or “contains a source of phenylalanine”. You will mostly find it in sugar-free drinks, chewing gum, light products, low-calorie desserts and tabletop sweeteners.
- Do not reason from one product only: look at the whole day.
- For children, check frequency and portions, not just presence.
- Do not assume replacing sugar with sweeteners is automatically neutral: it depends on the goal and context.
Conclusion
The 2023 IARC classification does not say that one aspartame drink causes cancer. It says there is a limited hazard signal. JECFA and EFSA, looking at risk and dose, keep a numerical threshold.
The useful choice is not panic or dismissal. It is reading the label, checking frequency and distinguishing occasional exposure from a daily pattern across several products.
Cited sources
- IARC, “Aspartame hazard and risk assessment results released”, 2023.
- JECFA, evaluation of aspartame and reaffirmation of the ADI of 0-40 mg/kg body weight/day, 2023.
- EFSA ANS Panel, “Scientific Opinion on the re-evaluation of aspartame (E951) as a food additive”, EFSA Journal, 2013.
- WHO, “Use of non-sugar sweeteners: WHO guideline”, 2023.
