Aspartame and cancer

The artificial sweetener aspartame has been classified as a substance that is possibly carcinogenic, which means it may cause cancer.

What is aspartame?

Aspartame is an artificial sweetener that food and drinks companies have used for many years to reduce the amount of added sugar in the products they sell, and to give people reduced-sugar options. It’s around 200 times sweeter than sugar, so much less is needed to match the sweetness of sugar.

It’s known by brand names around the world such as: NutraSweet, Equal, Pal Sweet and Canderel.

Which food and drink products contain aspartame?

It can be found in some diet versions of fizzy drinks, such as Coke Zero, Diet Coke and Pepsi Max.

Food manufacturers also use aspartame in products such as:

• flavoured yoghurts
• breakfast cereals
• granola bars
• sugar-free chewing gum
• low sugar desserts

You’ll need to look at each product’s ingredients list – check for the name aspartame or the E number (E951).

What’s the link between aspartame and cancer?

In 2023, the International Agency for Research on Cancer (IARC) and the Joint FAO/WHO Expert Committee on Food Additives (JEFCA) published a joint evaluation of the potential health risks from aspartame.

IARC looked at the evidence relating to the potential carcinogenic effects of aspartame. It found limited evidence that aspartame can cause cancer in humans. The evidence from animal studies and experimental studies was also limited. This is why it classified aspartame as “possibly carcinogenic”.

JECFA reviewed the general health and nutrition risks of aspartame at normal consumption levels. They found insufficient evidence linking aspartame to the risk of cancer or other diseases – such as type 2 diabetes and heart disease.

They concluded that the previous acceptable daily intake should not change (see below for what that is).

Why did IARC and JECFA carry out this work?

IARC and WHO each look at certain factors at regular intervals. IARC looks at something called “hazard identification”. This means trying to spot something that might cause harm or ill-health. It has not looked at aspartame before.

WHO analyses what the safe levels of a substance or factor are. The WHO last reviewed the evidence on aspartame in 1981.

How concerned should I be about the cancer risk of aspartame?

The new reports have categorised aspartame as “possibly carcinogenic to humans” and given it an evidence grading level known as 2B.

The evidence for a direct link between aspartame and cancer is not strong. This means that any harm from aspartame is likely to be small, especially when consumed within the “acceptable daily intake”.

What is the acceptable daily intake of aspartame?

The acceptable daily intake of aspartame – set by the World Health Organization (WHO) – is 0–40mg per kg body weight.

This works out as up to 2,800mg for a man of average weight (70kg). This is the same as drinking 9–14 cans of Diet Coke a day, assuming you don’t consume aspartame in any other products.

I’ve been drinking Diet Coke for years – am I going to get cancer?

The evidence that aspartame causes cancer is not strong, so the harm is likely to be low.

It’s rare that a single food or drink causes cancer. Cancer occurs because of a combination of behaviour over decades. This is alongside other factors – such as body weight, genetics and getting older.

One of our Cancer Prevention Recommendations is to limit consumption of sugar sweetened drinks, and to drink mostly water and unsweetened drinks. This is consistent with these evaluations.

Following our Cancer Prevention Recommendations is the best way to reduce the risk of developing a preventable cancer.

To cut down on sugar, I’ve been drinking diet soft drinks that contain artificial sweeteners. Should I switch back to full sugar versions?

These reports say you should consume aspartame within the “acceptable daily intake” and that this level doesn’t need to change.