On 4 February 2025 a coalition comprised of the consumer advocacy group Foodwatch, the French League Against Cancer(i.e., La Ligue contre le Cancer), and the mobile app company Yuka, launched a petition to prohibit the artificial sweetener aspartame in the EU, claiming that it is linked to cancer, cardiovascular disease, type 2 diabetes, and microbiome disorders.This article examines recent studies on the health impacts of aspartame and evaluates whether the findings would indeed justify the prohibition of aspartame on the basis of the EU’s “precautionary principle”.
Aspartame’s authorisation as an additive in the EU
Aspartame is a low-calorie artificial sweetener that is authorised to be used in the EU as a food additive under the E-number E 951 to sweeten foods and beverages and as a table-top sweetener, pursuant to Regulation (EC) No 1333/2008 of the European Parliament and of the Council on food additives. Aspartame is approximately 200 times sweeter than table sugar, so much lower amounts are needed to achieve the same level of sweetness. As such, aspartame is commonly used as a substitute for sugar in foods and beverages, especially those that are marketed as no- or low-calorie, such as in the “diet” versions of popular carbonated beverages.
The scientific controversy surrounding aspartame’s safety
Since its discovery in 1965, aspartame has been the subject of controversy due to concerns about its possible health impacts. As such, the US Food and Drug Administration, which was the first to approve aspartame in 1974 for use as a table-top sweetener and in chewing gum, cold breakfast cereals, and dry bases for certain foods, describes it as “one of the most studied food additives in the human food supply”.
In 2013, the European Food Safety Authority (hereinafter, EFSA) re-evaluated the safety of aspartame and concluded that aspartame and its breakdown products were safe for the general population, at current levels of exposure. The EFSA has been tasked with re-evaluating the safety of the salt of aspartame-acesulfame, a sweetener which is a mixture of aspartame and acesulfame K. The EFSA indicated that, as part of the re-evaluation, it would update its dietary exposure assessment of aspartame. The EFSA aims to publish its opinion within this year.
On 14 July 2023, the World Health Organization (hereinafter, WHO) released the results of two “independent but complementary” assessments of the health impacts of aspartame, conducted by the International Agency for Research on Cancer (hereinafter, IARC) and the Joint WHO/Food and Agriculture Organisation’s Expert Committee on Food Additives (hereinafter, JEFCA), respectively. On the one hand, the IARC concluded that aspartame was “possibly carcinogenic to humans”, citing “limited evidence” for cancer in humans (specifically for hepatocellular carcinoma, a type of liver cancer) and experimental animals, as well as “limited mechanistic evidence” that aspartame “exhibits key characteristics of carcinogens”. On the other hand, the JEFCA concluded that the acceptable daily intake of aspartame, namely 40 mg per kilogram of body weight per day, “does not pose a health concern”, as “with a can of diet soft drink containing 200 or 300 mg of aspartame, an adult weighing 70kg would need to consume more than 9-14 cans per day to exceed the acceptable daily intake, assuming there is no other intake from other food sources”.
The EU’s Precautionary Principle
The joint petition by Foodwatch, the French League Against Cancer, and Yuka calls on the European Commission (hereinafter, Commission) to prohibit aspartame on the basis of the “precautionary principle” set out in Article 7(1) of the EU’s Regulation (EC) No. 178/2002 laying down the general principles of food law, establishing the European Food Safety Authority and laying down procedures in matters of food safety, which states that “in specific circumstances where, following the assessment of available information, the possibility of harmful effects on health is identified but scientific uncertainty persists, provisional risk management measures necessary to ensure the high level of health protection chosen in the Community may be adopted, pending further scientific information for a more comprehensive risk assessment”.
The invocation of the precautionary principle appears to be misplaced, as it appears to be based on a misinterpretation of the term “possibly carcinogenic to humans”. The IARC emphasises that the term had no quantitative significance and was merely used as a descriptor of the strength of evidence of carcinogenicity in humans, and that “limited evidence” of carcinogenicity simply means that “a causal interpretation of the positive association observed in the body of evidence on exposure to the agent and cancer is credible, but chance, bias, or confounding could not be ruled out with reasonable confidence”. Notably, other agents that the IARC has classified as “possibly carcinogenic to humans” include aloe vera extract, gingko biloba extract, and pickled vegetables used in traditional Asian cuisine – none of which have generated the same amount of controversy as aspartame.
The difference between a hazard and a risk, and the regulatory relevance
When adopting measures pursuant to the precautionary principle, it is important to draw a distinction between hazard and risk. Under Article 3 of Regulation (EC) No. 178/2002 a hazard is “a biological, chemical or physical agent in, or condition of, food or feed with the potential to cause an adverse health effect”, while risk is “a function of the probability of an adverse health effect and the severity of that effect, consequential to a hazard”.
The IARC is not a food safety body and its responsibility is primarily to evaluate whether an agent is a cancer hazard, not to measure its cancer risk. Thus, the IARC’s assessment that aspartame is “possibly carcinogenic to humans” does not consider whether or not the levels of aspartame currently used in foods and beverage increase the risk of cancer (see Trade Perspectives, Issue No. 14 of 17 July 2023). The JEFCA, on the other hand, is a food safety body and, as such, assesses cancer risk. Its conclusion that “dietary exposure to aspartame does not pose a health concern” indicates that it did not consider aspartame to be a cancer risk.
With respect to food safety, the EU follows a risk-based, not hazard-based, approach. This means that the mere presence of an agent classified as a cancer hazard, such as aspartame, does not form the basis for ex-ante measures, such as a prohibition. Rather, the level of exposure to the agent and the probability of adverse effects must also be considered. The precautionary principle may only be invoked after all available information has been assessed and, crucially, when the possibility of harmful effects on health has been identified, but where scientific uncertainty still exists (see Trade Perspectives, Issues No. 21 of 20 November 2023 and No. 5 of 11 March 2024). In other words, there must already be a known risk to health.
To date, neither the JEFCA nor the EFSA have associated aspartame with any cancer risks that would justify the application of the precautionary principle. Therefore, prohibiting aspartame in the EU would be illegal, as well as, disproportionate, and unnecessary. And even if these entities were to uncover health risks in the future, an outright prohibition may nevertheless not be appropriate, as Article 7(2) of Regulation (EC) No. 178/2002 on the precautionary principle requires that any measures be “proportionate and no more restrictive of trade than is required to achieve the high level of health protection chosen in the Community”.
Any measure must also conform to Article 2 of the WTO Agreement on the Application of Sanitary and Phytosanitary Measures, which states that any measure applied to protect human health must be based on “scientific principles” and maintained on “sufficient scientific evidence”,“must not arbitrarily or unjustifiably discriminate between Members”, and “shall not be applied in a manner which would constitute a disguised restriction on international trade”, while Article 5 directs WTO Members to ensure that such measures are “not more trade-restrictive than required to achieve their appropriate level of sanitary or phytosanitary protection, taking into account technical and economic feasibility”. Therefore, before applying the precautionary principle, the EU must carefully consider both the scientific basis for the measure, as well as the measure’s conformity with the EU’s obligations under international agreements.
No prohibition in the immediate future?
The current lack of sufficient scientific evidence that aspartame does indeed increase the risk of cancer means that there is no legal basis for its prohibition in the EU. If aspartame were to be prohibited, its widespread use in various products means that manufacturers would need to seek substitutes – alternatives include neotame, an aspartame analogue, other “natural” sweeteners, like honey, stevia, and monkfruit, as well as “sugar alcohols”, such as xylitol, erythritol, and sorbitol. Manufacturers would incur significant costs in re-formulating and re-labelling their products.
Interested stakeholders should monitor the developments in relation to aspartame and the salt of aspartame-acesulfame. If new scientific evidence were to emerge confirming that aspartame does indeed pose a cancer risk, then the Commission would be required to take the necessary measures pursuant to Regulation (EC) No. 178/2002, including the removal of aspartame from the list of food additives pursuant to Regulation (EC) No 1333/2008.
