Science Editor Thomas Walsh asks whether there is validity to new claims regarding the safety of aspartame.
On 4 February 2025, World Cancer Day, an email appeared in the University Observer’s Science Editor’s inbox. The League Against Cancer, Yuka, and Foodwatch had launched a Europe-wide petition to ban the artificial sweetener aspartame, also known as E951. It has a similar calorific content to sugar per gram, but is 200 times sweeter so much less is added to soft drinks.
The groups involved claim that it’s a potential carcinogen. Foodwatch's Natacha Cingotti said that “since it has not yet been proven that aspartame is fully safe, it should no longer be authorised on the European market.” There is a distinct difference, however, between a product that has not been proven to be completely safe and a product that has been shown to be dangerous.
The European Food Safety Authority (EFSA) has been reviewing the available research into aspartame since the authority’s establishment in 2002. It has found Aspartame (and the products it breaks down to) to be safe for consumption by the general population, including infants, children, and pregnant women. The EFSA reaffirmed the safety of aspartame in 2006, 2009, 2013, and is currently examining all new research since the last review.
The EFSA reaffirmed the safety of aspartame in 2006, 2009, 2013, and is currently examining all new research since the last review.
The carcinogen claim comes from the International Agency for Research on Cancer, which recently classified aspartame as “possibly carcinogenic to humans” due to three studies showing a small but positive association between consumption of artificially sweetened beverages and the risk of liver cancer. Correlation does not mean causation, and the agency could not rule out confounding factors, such as lifestyle, or even pure chance as an explanation. The Joint Food & Agricultural Organisation / World Health Organisation Expert Committee on Food Additives also recently found no convincing evidence of adverse effects.
Aspartame's reputation for safety is partially due to the fact that when ingested, aspartame breaks down into metabolites that are also obtained after consuming common foods and drinks. One such metabolite is methanol, which can cause liver damage. The amount of methanol produced from the breakdown of aspartame is trivial, even compared to other safe foods like fruit and vegetables.
While there are other areas of concern that may merit further research, such as altered gut microbiota, induced appetite, and mood changes, there currently isn’t conclusive evidence. Aspartame remains in the same risk category as pickled vegetables and aloe vera, and readers likely have more pressing things to worry about.