As forecast in June, the cancer-research arm of the World Health Organization (WHO) has officially named the non-sugar sweetener aspartame as possibly carcinogenic to humans.
The International Agency for Research on Cancer (IARC), after assessment with WHO, the Food and Agriculture Organization (FAO) and the Joint Expert Committee on Food Additives (JECFA), has added the common artificial sweetener to Category 2B, aka “possibly carcinogenic to humans,” which also features aloe vera extracts and traditional Asian pickled vegetables.
For context, the highest-risk Category 1, “carcinogenic to humans,” includes tobacco, ultraviolet light and processed meats such as bacon and hotdogs. And Category 2A, “probably carcinogenic to humans,” features high-temperature frying and red meat such as beef and lamb.
“There was no convincing evidence from experimental or human data that aspartame has adverse effects after ingestion, within the limits established by previous committee,” said Francesco Branca, director of the WHO Department of Nutrition and Food Safety, in Geneva, Switzerland on July 12.
The classification comes after analysis of more than 1,300 research papers concluded that there was “limited” evidence of the substance’s carcinogenicity in humans, providing daily intake did not exceed 40 mg/kg body weight.
For someone who weighs around 150 lb (68 kg), they’d need to drink in excess of nine cans of aspartame-sweetened soda a day. However, scientists caution that because aspartame, a low-calorie sugar substitute, is used in more than 6,000 products across the globe, including in toothpaste and chewable vitamins, unknown consumption of the sweetener can easily happen.
“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,” said Mary Schubauer-Berigan of the IARC Monographs program.
The findings noted there was limited evidence for hepatocellular carcinoma (a type of liver cancer) in humans, limited evidence for cancer in experimental animals and limited evidence related to possible mechanisms for causing cancer.
“The IARC’s classification was based on three observational studies of liver cancer based on self-reported aspartame consumption,” said Dr Ian Musgrave, senior lecturer in the Faculty of Medicine, University of Adelaide, Australia. “The data was not consistent between the different studies and given uncertainties about doses and other factors that impact cancer, this finding could be just statistical noise.”
However, aspartame has been linked to other health issues, including disruption to the gut microbiome, blood sugar regulation and potential weight gain.
Its usefulness in ‘diet’ food and drinks has also been questioned, with earlier research finding that the substance, which is 200 times sweeter than sugar, spikes sugar cravings.
“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,” said Dr Moez Sanaa, WHO Head of the Standards and Scientific Advice on Food and Nutrition Unit. “We need better studies with longer follow-up and repeated dietary questionnaires in existing cohorts. We need randomized controlled trials, including studies of mechanistic pathways relevant to insulin regulation, metabolic syndrome and diabetes, particularly as related to carcinogenicity.”
“Cancer is one of the leading causes of death globally,” added Branca. “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. 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.”
While some regions continue to move away from using aspartame in products, the science world says there’s no need to pour your Pepsi Max down the sink just yet.
"For current consumers of diet drinks, this news isn’t cause for major alarm,” said Alexandra Jones, from independent research body, The George Institute for Global Health. “The work from JECFA confirms that normal levels of consumption appear to be safe.”
The US Food and Drug Administration (FDA), which approved aspartame for use back in 1974, has rejected the IARC assessment, saying this and other artificial sweeteners are safe for consumption under current guidelines.
“Aspartame is one of the most studied food additives in the human food supply,” a spokesperson noted. “FDA scientists do not have safety concerns when aspartame is used under the approved conditions.”