Aspartame, which can be found in products ranging from Coca-Cola diet sodas to Mars' Extra chewing gum and Snapple drinks, will be classed next month as "possibly carcinogenic to humans" for the first time by the World Health Organization's (WHO) cancer research department, the International Agency for Research on Cancer (IARC), Reuters reported, citing two informed sources.

The news agency noted that the IARC ruling however does not take into account the safe quantity that a person can consume. This information would come from a separate WHO expert committee on food additives -- the JECFA (the Joint WHO and Food and Agriculture Organization's Expert Committee on Food Additives), Reuters indicated.

JECFA began reviewing Aspartame at the end of this month and will be announcing its findings on the same day the IARC releases its decision on July 14.

JECFA has considered Aspartame safe to consume within accepted daily limits since 1981 and has been widely shared by national regulators in the US and Europe. For instance, an adult weighing 60 kg (132 pounds) would have to drink, depending on the quantity of Aspartame, between 12 and 36 cans of diet soda daily to be at risk.

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Although the findings of both the IARC and JECFA were confidential until July, an IARC spokesperson said they were "complementary", with IARC's conclusion representing "the first fundamental step to understand carcinogenicity". The JECFA 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."

Warnings against 'leaked opinion'

Nozomi Tomita, an official from Japan's Ministry of Health, Labour and Welfare, wrote to WHO's deputy director general, Zsuzsanna Jakab, in a letter on March 27: "We kindly ask both bodies to coordinate their efforts in reviewing Aspartame to avoid any confusion or concerns among the public". 

In 2015, the IARC committee concluded that glyphosate is "probably carcinogenic". Germany’s Bayer firm back in 2021 lost its third appeal against US court verdicts that awarded damages to consumers blaming cancer on the use of its glyphosate-based weedkillers.

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IARC decisions have faced criticism in the past over needless alarms such as putting overnight working and consuming red meat into its "probably cancer-causing" class and mobile phones as "possibly cancer-causing".

Frances Hunt-Wood, the secretary general of the International Sweeteners Association (ISA), considered that the "IARC is not a food safety body and their review of Aspartame is not scientifically comprehensive and is based heavily on widely discredited research".

The ISA, whose members include Mars Wrigley, a Coca-Cola unit, said it had "serious concerns with the IARC review, which may mislead consumers".

The International Council of Beverages Associations' executive director, Kate Loatman, raised the alarm that health authorities should be "deeply concerned" by the "leaked opinion", warning that it "could needlessly mislead consumers into consuming more sugar rather than choosing safe no-and low-sugar options."

The myth of sweetener and weight loss?

Aspartame has been a previous study subject as an observational study in France last year showed that those who consumed large amounts of artificial sweeteners such as Aspartame had a slightly higher cancer risk.

The study, published in the journal PLOS Medicine, said that higher cancer risk was particularly seen with sweeteners Aspartame and acesulfame potassium -- both used in many soft drinks including Coke Zero.

However, experts not involved in the research said there is not enough proof to consider changing current health advice.

Aspartame is authorized for global use and major food and beverage firms have defended using it for decades.

However, PepsiCo removed Aspartame from its sodas in 2015, bringing it back a year later, and removing it again in 2020.

Sources close to the IARC state that listing Aspartame as a possible carcinogen will motivate further research which in turn will help agencies, consumers and manufacturers draw stronger conclusions. It will potentially ignite debate once again over the IARC's role and the safety of sweeteners in general.

The WHO published last month's guidelines advising against the use of non-sugar sweeteners for weight control which caused outrage in the food industry since they argue that it can be helpful for those wanting to reduce sugar in their diet.