A popular artificial sweetener used in thousands of products worldwide including Diet Coke, ice-cream and chewing gum is to be declared a possible cancer risk to humans, according to reports.

The World Health Organization’s cancer research arm, the International Agency for Research on Cancer (IARC), has conducted a safety review of aspartame and will publish a report next month.

It is preparing to label the sweetener as “possibly carcinogenic to humans”, Reuters reported on Thursday. That would mean there is some evidence linking aspartame to cancer, but that it is limited. The IARC has two more serious categories, “probably carcinogenic to humans” and “carcinogenic to humans”.

The move is likely to prove controversial. The IARC has faced criticism for causing alarm about hard-to-avoid substances or situations.

It previously put working overnight and consuming red meat into its probably cancer-causing class, and listed using mobile phones as possibly cancer-causing.

The IARC safety review was conducted to assess whether or not aspartame is a potential hazard, based on all the published evidence, a person familiar with the matter told the Guardian. However, it does not take into account how much of a product a person can safely consume.

That advice comes from a separate WHO expert committee on food additives, the Joint FAO/WHO Expert Committee on Food Additives (Jecfa), which has also been reviewing aspartame use this year. It is due to announce its findings on the same day the IARC makes public its decision, on 14 July.

“IARC has assessed the potential carcinogenic effect of aspartame (hazard identification),” an IARC spokesperson confirmed to the Guardian. “Following this, the joint FAO/WHO expert committee on food additives will update its risk assessment exercise on aspartame, including the reviewing of the acceptable daily intake and dietary exposure assessment for aspartame. The result of both evaluations will be made available together, on 14 July 2023.”

Aspartame has been widely used since the 1980s as a table-top sweetener, and in products such as diet fizzy drinks, chewing gum, breakfast cereals and cough drops.

It is authorised for use globally by regulators who have reviewed all the available evidence, and major food and beverage makers have for decades defended their use of it.

The food industry expressed serious concerns about the reports on Thursday.

“IARC is not a food safety body,” said Frances Hunt-Wood, the secretary general of the International Sweeteners Association. “Aspartame is one of the most thoroughly researched ingredients in history, with over 90 food safety agencies across the globe declaring it is safe, including the European Food Safety Authority, which conducted the most comprehensive safety evaluation of aspartame to date.”

The International Council of Beverages Associations executive director, Kate Loatman, suggested the move “could needlessly mislead consumers into consuming more sugar rather than choosing safe no- and low-sugar options”.

There is existing evidence that raises questions about the potential impact of aspartame on cancer risk. A study in France involving about 100,000 adults last year suggested those who consumed larger amounts of artificial sweeteners including aspartame had a slightly higher cancer risk. A study from the Ramazzini Institute in Italy in the early 2000s reported that some cancers in mice and rats were linked to aspartame.

The Guardian understands the IARC collected 7,000 research references to aspartame, and included 1,300 studies in the package of materials assessed by experts. “We really need to wait and see the full IARC evaluation before we can make any firm conclusions,” said Oliver Jones, a professor of chemistry at RMIT University in Melbourne, Australia. “Without that we are really shooting in the dark.”

Prof Kevin McConway, emeritus professor of applied statistics at the Open University, said an IARC label of being possibly carcinogenic “does not mean that a substance actually presents a risk to humans in normal circumstances”.

The more important finding would be what Jecfa concluded about aspartame intake, he said.

“Back in 1981 they established an acceptable daily intake of aspartame, of 40 milligrams per kilogram of body weight per day. To consume over that limit would require a very large daily consumption of Diet Coke or similar drinks. On 14 July, Jecfa may change that risk assessment, or they may not.”

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