Do artificial sweeteners cause cancer and are there other concerns?

Fresh concerns have been raised over the potential for the sweetener aspartame to cause liver cancer

By Clare Wilson

14 July 2023

Sweeteners such as aspartame are often added to diet sodas

Kazitafahnizeer/Shutterstock

Two reports on the sweetener aspartame came out this week, noting that some research has linked its consumption to liver cancer. This comes after the World Health Organization (WHO) advised most people to avoid most kinds of “non-sugar sweeteners”, after a 2022 review of the evidence found they don’t help with weight control long term and may cause diabetes, heart attacks and death.

Which sweeteners are the concern?

In May, the WHO said most sweeteners are problematic, both artificial ones, such as aspartame and saccharin, as well as ones made from plants, such as stevia. The exception is sweeteners made from sugar alcohols called polyols, which don’t fall under the “non-sugar sweeteners” umbrella and weren’t included in the review.

Does aspartame carry any extra risk?

Two separate international bodies this week issued reports on the long-used sweetener aspartame and they are seemingly somewhat contradictory. The WHO’s International Agency for Research on Cancer (IARC) has classified the substance as “possibly carcinogenic”, which sounds alarming, but actually means there is limited – and not convincing – evidence that it could be a cause of liver cancer.

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A separate report, from the WHO and the Food and Agriculture Organization Joint Expert Committee on Food Additives concluded that there was no reason to change its existing recommendations on aspartame consumption. This advice says it is safe for people to have up to 40 milligrams of aspartame per kilogram of their body weight, which would be up to 14 cans of diet soft drinks a day for someone who weighs 70 kilograms.

“The findings of limited evidence of carcinogenicity in humans and animals, and of limited mechanistic evidence on how carcinogenicity may occur, underscore the need for more research to refine our understanding on whether consumption of aspartame poses a carcinogenic hazard,” said Mary Schubauer-Berigan at the IARC Monographs programme in a statement.

Would it be safer to avoid all sweeteners altogether?

The idea is that food and drinks with sweeteners help people reduce their sugar intake, as too much sugar is linked with higher weight, type 2 diabetes and heart disease. The trouble is that the evidence supporting this is mixed. Some short, randomised trials have found that consuming drinks with sweeteners instead of the full-sugar versions can reduce weight gain in children, but others have failed to show a benefit.