Reviews by two World Health Organisation bodies have found there is limited evidence the sweetener aspartame can cause cancer. The International Agency for Research on Cancer (IARC) found “limited evidence” for carcinogenicity while the Joint Expert Committee on Food Additives (ECFA) reaffirmed the acceptable daily intake.
Aspartame is an artificial (chemical) sweetener widely used in various food and beverage products since the 1980s, including diet drinks, chewing gum, gelatine, ice cream, dairy products such as yogurt, breakfast cereal, toothpaste and medications such as cough drops and chewable vitamins.
IARC classified aspartame as possibly carcinogenic to humans (IARC Group 2B) and JECFA reaffirmed the acceptable daily intake of 40 mg/kg body weight, which equates to a 70kg adult needing to consume more than 9-14 cans of diet soft drink a day to exceed it.
WHO Department of Nutrition and Food Safety director, Dr Francesco Branca, said, “The assessments of aspartame have indicated that, while safety is not a major concern at the doses which are commonly used, potential effects have been described that need to be investigated by more and better studies.
“Cancer is one of the leading causes of death globally. Every year, one in six people die from cancer. Science is continuously expanding to assess the possible initiating or facilitating factors of cancer, in the hope of reducing these numbers and the human toll.”
This was the first review for IARC, possibly prompted by a 2022 study that mentioned liver cancer, and the third for JECFA, with the reviews conducted independently. Both noted there were limitations in the available evidence for cancer and other health effects.
The IARC and JECFA evaluations on aspartame’s impact were based on scientific data collected from a range of sources, including peer-reviewed papers, governmental reports, and studies conducted for regulatory purposes. The studies were reviewed by independent experts, and both committees took steps to ensure the independence and reliability of their evaluations.
IARC classified aspartame as possibly carcinogenic to humans (Group 2B) based on limited evidence for cancer in humans (specifically hepatocellular carcinoma, a type of liver cancer). There was also limited evidence for cancer in experimental animals and limited evidence related to the possible mechanisms for causing cancer.
University of Sydney honorary Associate Dr Alan Barclay said the quality of the evidence underpinning IARC’s assessment is not high, so the conclusion can be 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 average Australian consumes less than 10 per cent of the ADI and even the biggest consumers have less than 25 per cent of the ADI,” Barclay said.
He added that Australian’s intake of aspartame is also likely to be decreasing due to the rising popularity of alternatives including stevia and monk fruit.
IARC hazard assessment
WHO said IARC’s hazard identifications are the first fundamental step to understand the carcinogenicity of an agent, by identifying its specific properties and potential to cause harm. Its evaluation looks at all types of exposure, e.g., dietary, or occupational.
“Classifications reflect the strength of scientific evidence as to whether an agent can cause cancer in humans, but they do not reflect the risk of developing cancer at a given exposure level,” it said.
A Group 2B classification is the third highest level out of four. It is generally used either when there is there is limited, but not convincing, evidence for cancer in humans, or convincing evidence for cancer in experimental animals, but not both.
IARC Monographs programme head Dr Mary Schubauer-Berigan said, “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.”
JECFA risk assessment
JECFA concluded that the data evaluated indicated no sufficient reason to change the previously established acceptable daily intake (ADI) of 0–40 mg/kg body weight for aspartame. The committee therefore reaffirmed that it is safe for a person to consume within this limit per day.
“For example, with a can of diet soft drink containing 200 or 300 mg of aspartame, an adult weighing 70kg would need to consume more than 9–14 cans per day to exceed the acceptable daily intake, assuming no other intake from other food sources,” it said.
JECFA’s risk assessments determine the probability of a specific type of harm, i.e., cancer, to occur under certain conditions and levels of exposure. It is not unusual for JECFA to factor IARC classifications into its deliberations, WHO said.
Standards and Scientific Advice on Food and Nutrition Unit head Dr Moez Sanaa said, “JECFA also considered the evidence on cancer risk, in animal and human studies, and concluded that the evidence of an association between aspartame consumption and cancer in humans is not convincing.
“We need better studies with longer follow-up and repeated dietary questionnaires in existing cohorts. We need randomised controlled trials, including studies of mechanistic pathways relevant to insulin regulation, metabolic syndrome, and diabetes, particularly as related to carcinogenicity.”
CEO of the Australian Beverages Council, Geoff Parker, told Food & Drink Business it is important to recognise IARC looks at hazard identification while JECFA looks at risk. A hazard means possible harm, even if unlikely, while a risk is the likelihood of that harm occurring.
“We rely on world-leading food standard setting agencies like FSANZ, the US FDA, Health Canada, and the European Food Safety Authority, which have been reviewing ingredients like aspartame for well over 40 years and continue to determine them safe at the appropriate average daily intake.
“Those agencies and risk assessments look at the totality of the evidence base and human exposure,” Parker said.
RMIT University professor of chemistry Oliver Jones explains the hazard/risk relationship as like driving a car.
“There is definitely a hazard; cars crash, and people get injured, and even die, but the risk of that happening when you drive to the shops or take the kids to school is fairly low, most of us don’t think about it – even though the risk is not zero.
“IARC only looks at hazard, which in this case means they just looked to see if there was any evidence that aspartame might be linked to cancer. They do not make an assessment of how likely the hazard is to occur,” Jones said.
He added it was worth remembering we are all exposed to carcinogens every day.
“It sounds scary but it’s about risk. Even things that the IARC classifies as class one carcinogens, such as UV light and alcohol, do not cause cancer instantly just because you are exposed to them once. For example, if you get too much sun on the beach in summer you might get sunburn, but you’ll recover. If you continually sunbathe with no sun protection, then your risk of skin cancer goes up,” Jones said.
Parker pointed out that there is a risk of consumers being more confused and concerned by the findings and in looking for other alternatives return to the same drink but made with sugar.
“That is contrary to broader public health agendas around people consuming less sugar and calories,” he said.
IARC and WHO said they will continue to monitor new evidence and encourage independent research groups to develop further studies on the potential association between aspartame exposure and consumer health effects.
