Key Points
- Artificial sweetener aspartame will be listed as possibly carcinogenic to humans by the WHO.
- Aspartame is one of the world's most common sweeteners.
- WHO's decision would be contrary to regulators and the food industry.
One of the world's most common artificial sweeteners is set to be declared as possibly causing cancer in humans by a leading global health body, according to two sources with knowledge of the process, pitting it against the food industry and regulators.
Aspartame, used in products from Coca-Cola diet sodas to Mars' Extra chewing gum, will be listed in July as "possibly carcinogenic to humans" for the first time by the International Agency for Research on Cancer (IARC), the World Health Organization's (WHO) cancer research arm, the sources told Reuters.
But several scientists with expert knowledge in the matter said aspartame is not necessarily so unsafe that it shouldn't be consumed at all.
The IARC ruling, finalised earlier this month after a meeting of the group's external experts, is intended to assess whether something is a potential hazard or not, based on all the published evidence.
It does not take into account how much of a product a person can safely consume.
This advice for individuals comes from a separate WHO expert committee on food additives, the Joint WHO and Food and Agriculture Organization's Expert Committee on Food Additives (JECFA), alongside determinations from national regulators.
Since 1981, JECFA has said aspartame is safe to consume within accepted daily limits.
For example, an adult weighing 60 kg would have to drink between 12 and 36 cans of diet soft drink – depending on the amount of aspartame in the drink – every day to be at risk.
Its view has been widely shared by national regulators, including in the United States and Europe.
What do Australian experts say about aspartame?
Dr Slade Matthews, a lecturer in pharmacology at the University of Sydney, said the proposed label is "not strong and does not suggest that we should all stop consuming aspartame-containing products altogether".
The common artificial sweetener aspartame will be labelled a 'possible cancer risk' by the World Health Organization. Source: AAP / Richard B. Levine/PA/Alamy
"From a toxicological perspective, this could serve as a heads-up for people who habitually drink several cans of soft drinks per day for them to drink more water."
Oliver Jones, a chemistry professor at RMIT University, said the complete IARC evaluation needs to be seen before making any firm conclusions.
The listing of aspartame as a "possible carcinogen" will only mean "there is some evidence that it can cause cancer in humans, but at present, it is far from conclusive. But we really can’t be sure of anything until a formal announcement is made," he said.
Mr Jones noted that the degree of exposure to something that may possibly cause cancer is important to consider.
"Like other food additives, aspartame had to undergo robust safety evaluation before it was approved for use in food. It is the world's most widely used artificial sweetener, and current evidence is that it is safe at current levels of consumption," he said.
But Mark Wahlqvist, former president of the International Union of Nutritional Sciences, said the IARC's advice and concerns on using non-nutritive sweeteners are a general health warning, not just around cancer risks.
"There is now no acceptable public health justification for their promotion in weight management," he said.
"Preference for sweetness itself, over and above sugar as a nutrient, is a consideration, given the extent of human biology for sweet receptors beyond the tongue, in other organs and the gut microbiome," Mr Wahlqvist said.
What happens next?
Similar IARC rulings in the past for different substances have raised consumer concerns about their use, led to lawsuits, and pressured manufacturers to recreate recipes and switch to alternatives. That has led to criticism that the IARC's assessments can confuse the public.
JECFA, the WHO committee on additives, is also reviewing aspartame use this year. Its meeting began at the end of June, and it is due to announce its findings on the same day that the IARC makes public its decision – on 14 July.
An IARC spokesperson said both the IARC and JECFA committees' findings were confidential until July but added they were "complementary", with IARC's conclusion representing "the first fundamental step to understand carcinogenicity".
The additives committee "conducts risk assessment, which determines the probability of a specific type of harm (e.g. cancer) to occur under certain conditions and levels of exposure".
The industry and regulators fear that holding both processes at around the same time could be confusing, according to letters from the US and Japanese regulators seen by Reuters.
"We kindly ask both bodies to coordinate their efforts in reviewing aspartame to avoid any confusion or concerns among the public," Nozomi Tomita, an official from Japan's Ministry of Health, Labour and Welfare, wrote in a letter dated 27 March to WHO's deputy director general, Zsuzsanna Jakab.
The letter also called for the conclusions of both bodies to be released on the same day, as is now happening.
The Japanese mission in Geneva, where the WHO is based, did not respond to a request for comment.
