WHO says aspartame can cause cancer, but safe in moderation

New concerns about the safety of aspartame, one of the most widely used artificial sweeteners, have emerged following its classification as a “potential carcinogen” by the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC).

Despite this, another WHO agency has stuck to its existing guidance on safe daily aspartame intake, emphasizing the substance does not absorb into the bloodstream.

The dichotomy within the UN’s health authority has reignited debates about aspartame’s safety, an ingredient found in products ranging from diet sodas to toothpaste, chewing gum, gelatin, ice cream, dairy products such as yogurt, breakfast cereal, and medications such as cough drops and chewable vitamins.

Despite its approval for consumption in over 90 countries and five reviews by the US Food and Drug Administration (US FDA) since 1981, worries about its potential cancer risk persist.

The US FDA, alongside governmental bodies and the food industry, is pushing back against the IARC’s conclusion, arguing the studies used are flawed.

“The FDA is aware of the IARC and JECFA conclusions about aspartame. Aspartame being labeled by IARC as ‘possibly carcinogenic to humans’ does not mean that aspartame is actually linked to cancer,” the US drug regulator said in response to a query from Press Insider.

The agency underscores that aspartame is among the most thoroughly studied food additives, and its use is vital for consumers aiming to reduce sugar intake.

“The FDA disagrees with IARC’s conclusion that these studies support classifying aspartame as a possible carcinogen to humans. FDA scientists reviewed the scientific information included in IARC’s review in 2021 when it was first made available and identified significant shortcomings in the studies on which IARC relied. We note that JECFA did not raise safety concerns for aspartame under the current levels of use and did not change the Acceptable Daily Intake (ADI),” it said.

“Aspartame is one of the most studied food additives in the human food supply. FDA scientists do not have safety concerns when aspartame is used under the approved conditions. The sweetener is approved in many countries. Regulatory and scientific authorities, such as Health Canada and the European Food Safety Authority have evaluated aspartame and also consider it safe at current permitted use levels,” it added.

To be sure, the IARC and the Joint Expert Committee on Food Additives (JECFA) are not at odds, as they serve different functions. The IARC evaluates cancer-causing potential, while the JECFA assesses actual human risk.

Meanwhile, Francesco Branca, director of the WHO’s Department of Nutrition and Food Safety, advised consumers to moderate sugar and sweetener intake and opt for water.

“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,” Branca said.

The JECFA reiterated the acceptable daily aspartame intake despite growing concerns over its prevalence in many foods.

“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,” JECFA said in a statement.

Aspartame is used in about 95% of sweetened carbonated soft drinks and at least 90% of ready-to-drink teas.

IARC’s classification draws on two significant studies, one from France and another from Italy, both facing criticism for their methodologies. The studies found potential links between aspartame consumption and a higher cancer risk in both humans and animals.

Despite the pushback, some experts see the IARC’s warning as a wakeup call amid the global proliferation of highly processed foods. Advocates call for regulatory action and industry reformulation with safer alternatives, to alleviate the burden of decision-making from consumers.

IARC identifies cancer-causing hazards by investigating their unique characteristics. While its classifications don’t quantify cancer risk at specific exposure levels, they highlight the strength of scientific evidence linking agents to cancer.

Factors such as diet and occupational exposure are considered, with a group 2B ranking indicating limited evidence in humans or strong evidence in animals. These findings set the stage for our upcoming analysis of their broader implications.

“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,” Dr Mary Schubauer-Berigan of the IARC Monographs program said.