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Aspartame and cancer: what the evidence says

Aspartame and cancer: what the evidence says


The World Health Organisation has labelled a low-calorie sweetener that’s in soft drinks, chewing gum and ice cream as “possibly carcinogenic”. A carcinogen is something capable of causing cancer. But what does the ruling mean in reality?

Aspartame may not be part of your daily vocabulary, but it’s almost certainly part of your daily diet. 

The low-calorie sweetener is 200 times more powerful than sugar and was approved for use in food in the 1970s. 

Now it is in more than 5,000 products including soft drinks, chewing gum and ice cream, but last week the World Health Organisation officially classified aspartame as a “possible carcinogen”.

The decision was made by the International Agency for Research on Cancer, which has four categories of potential risk. The first includes things that definitely cause cancer, like tobacco, alcohol and exposure to sunlight.

The second includes “probable” hazards, like red meat. Aspartame now sits one tier below that alongside aloe vera, pickled vegetables and carpentry as a “possible carcinogen”. That means there have been some studies suggesting that they pose a potential risk to humans, but the research is limited. 

An Italian study in the early 2000s found that mice who ate over 50 times the recommended human daily allowance of aspartame experienced malignant tumours at higher rates than those that didn’t. But those results were called into question by the European Food Safety Authority in 2009, which said there was no indication that the sweetener caused the cancer.

Researchers have also looked at aspartame and its effect on humans. Last year, a French study showed slightly increased cancer risks in people who consumed very large amounts of the sweetener. Those results have been disputed too.

All of this has still been enough to prompt the WHO to look into aspartame, and part of the reason for labelling it “possibly carcinogenic” is to hopefully bring about more research in this area.

The WHO first issued guidance on the recommended daily allowance of aspartame in 1981 and its new categorisation does not change that advice.

It remains safe to consume within current recommended daily limits – 40 milligrams of aspartame per kilogram of body weight per day, which would be 9-14 cans of diet soda a day. Until we know more, the WHO is clear that companies shouldn’t withdraw products containing aspartame and the public can carry on consuming them in moderation.

Today’s episode was written and mixed by Patricia Clarke.