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“Limited” evidence for cancer risk from common sweetener aspartame – Expert Reaction

Two World Health Organization bodies have conducted independent reviews, concluding there is only limited evidence a sweetener used in many diet fizzy drinks could cause cancer. 

The International Agency for Research on Cancer (IARC) has classified aspartame as “possibly carcinogenic to humans” indicating that there is limited evidence that aspartame is carcinogenic in humans and experimental animals, and limited evidence that it exhibits the key characteristics of a carcinogen.

At the same time, the Joint Expert Committee on Food Additives (JECFA) reaffirmed the acceptable daily intake of 40 mg/kg body weight – meaning a 70kg adult would need to consume more than 9–14 cans of diet soft drink per day to exceed it.

The SMC asked local experts to comment on the research.

Dr Andrea Teng, Senior Research Fellow, Department of Public Health, University of Otago, comments:

“Aspartame has been classified as possibly carcinogenic to humans by the International Agency for Research on Cancer, World Health Organization.

That means its safety at current doses is not a major concern and we need to do more and better research to understand its effects. To put this in context, the evidence is stronger for the links between alcohol and cancer, or red meat and cancer.

Sugary drinks are the bigger problem. There is good evidence for an association of sugary drinks with diabetes, dental decay, and other chronic diseases. But they have not been reviewed by IARC.

The problem with studying diet drinks containing aspartame is that people may be selecting these products because they are already at high risk of nutrition related disease, and they want to reduce that risk. So it can be difficult to untangle these effects.

We need urgent action to improve our food environment in New Zealand.”

No conflict of interest

Our colleagues at the Australian Science Media Centre have also gathered expert comments on the research.

Dr Alexandra Jones, Senior Research Fellow (Food Policy and Law) at The George Institute for Global Health, comments:

“For current consumers of diet drinks, this news isn’t cause for major alarm. Aspartame has been classed in IARC’s Category 2B, which means there’s limited evidence that it might cause cancer, not that it does or is likely to. The work from JECFA confirms that normal levels of consumption appear to be safe.

“Beyond this focus on aspartame and cancer specifically, we know the use of sweeteners in our food supply is increasing – in Australia for example, the food industry has been turning away from aspartame for some time, with more use of ‘natural’ sweeteners such as Stevia. As governments and consumers have looked to reduce sugar intake, we’re seeing an increase in sweetener use across the food supply – not just in drinks. It’s important that we continue to study the long-term effects of this on a range of health outcomes. Given other recent guidance from the World Health Organization that non-sugar sweeteners should not be used as a means of achieving weight control or reducing the risk of heart disease or diabetes, it might still be wise to think about the overall benefits to health (and your wallet) from trading a soft drink habit of any kind for healthier alternatives such as tap water.”

No conflict of interest

Clare Hughes, Chair of Cancer Council’s Nutrition, Alcohol and Physical Activity Committee, comments:

“The IARC classification and JECFA determination means that aspartame is possibly carcinogenic, if consumed in large amounts. However, recent Australian research suggests the use of aspartame in the Australian food supply is declining and that most Australians are not consuming aspartame at the levels considered unsafe. This classification of aspartame is, however, a timely reminder for Australians to consider the choices they make when it comes to what they eat and drink.

“We know that 2 in 3 Australian adults are living with overweight or obesity, increasing their risk of 13 types of cancers. While ‘sugar-free’ or ‘diet’ drinks containing intense sweeteners might once have been marketed as a means of weight management, recent evidence shows that replacing sugars with intense low-kilojoule sweeteners does not support weight management in the long term and is potentially associated with increased risk of type 2 diabetes and cardiovascular diseases.

“What Australians can do to lower their risk of cancer is maintain a healthy diet with minimal processed foods, be physically active every day for at least 30 minutes, quit smoking and limit their alcohol use. By following these recommendations, Australians can decrease their cancer risk and live long and healthy lives.”

No conflict of interest

Dr Alan Barclay, Honorary Associate at The University of Sydney comments:

“IARC has re-analysed old studies and come to the conclusion that the intense sweetener aspartame is “possibly carcinogenic to humans” (Group 2B). The quality of evidence that underpins this assessment (mostly based on rodent studies) is not high and the conclusion can of course by challenged.

“Regardless, like most things in life, dose matters. The JECFA have reaffirmed the Acceptable Daily Intake (ADI) of 40 mg/kg body weight per day which has been in place in Australia since aspartame was approved for use in foods and beverages in the 1980s. The most recent FSANZ diet exposure assessment determined that the the average Australian consumes less than 10% of the ADI and even the biggest consumers have less than 25% of the ADI”

“Since this survey was conducted, other intense sweeteners have been approved including “stevia” and “monk fruit”, and have been popular as they are perceived as more natural alternatives.

“Australian population intakes of aspartame are therefore well below the ADI, and likely to be decreasing due to the popularity of other alternatives. Therefore, even the most avid users are not likely to be at increased risk of cancer from aspartame in Australia.

“Finally, to put the IARC conclusion into perspective, aspartame will be grouped with other Group 2B foods/additives like pickled (Asian) vegetables, the colour amaranth and preservative Butylated hydroxyanisole (BHA). However, processed meats like ham, bacon and hot dog sausages are classified as Group 1 carcinogens and red meat is classified as Group 2A, indicating that they represent a higher risk for consumers than aspartame.”

Conflict of interest: Alan is the co-author of the book The Ultimate Guide to Sugars and Sweeteners