Aspartame intake and cancer risk: What you need to know

Aspartame is a low-calorie sweetener that is approximately 200 times sweeter than sugar and is used to replace sugar and provide sweetness in energy-reduced food, or food with no added sugars. Recent news stories have raised the alarm that aspartame may be linked to cancer, but there are a few things to keep in mind when reading the headlines.

The study behind the headlines

The report behind the news was released by the International Agency for Research on Cancer (IARC) an agency of the World Health Organization (WHO), as part of their ongoing program to identify and classify environmental factors that may be carcinogenic to humans.

As part of their process the IARC expert group assessed all publically available studies related to cancer in humans and animal experiments on the sweetener aspartame. In three observational studies in humans, they observed a link between consumption of artificially sweetened drinks and the risk of liver cancer. They also found limited evidence for cancer in animal studies but noted that they had concerns about the quality of the animal studies. This led them to classify aspartame as "possibly carcinogenic to humans" (a Group 2B carcinogen). The strength-of-evidence classification in Group 2B is the third highest level out of four levels. This category is generally used when there is either limited but no convincing evidence for cancer in humans or convincing evidence for cancer in experimental animal studies, but not both.

In parallel, the Joint FAO/WHO Expert Committee on Food Additives (JEFCA) carried out a risk assessment for aspartame and cancer in humans and concluded that it is safe for people to consume aspartame within their previously established acceptable daily intake (ADI) of 0-40 mg/kg body weight.

What to keep in mind when reading the study's conclusions?

• IARC monograph program conducts hazard assessments, while JEFCA conducts risk assessments.

The IARC carried out a hazard assessment, a process for assessing whether a chemical can cause cancer, not whether it is likely to under real-use conditions. Based on this process, IARC classifies chemicals or other environmental factors into one of four different categories. These are Group 1 (carcinogenic to humans), Group 2A (probably carcinogenic to humans), Group 2B (possibly carcinogenic to humans). Group 3 (not classifiable as to its carcinogenicity to humans). This classification systems tells us whether a chemical has the potential to cause cancer, but it does not tell us about how likely it is to cause cancer when used under real-life conditions. In other words, the IARC categories tell us whether an exposure can cause cancer but not the dose required, the route of exposure, nor the increase in risk.

As with all risks, the exposure level is key to determining the level or risk. In other words, how much aspartame people are consuming is important. The JEFCA panel carried out a risk assessment, a process which determines how likely it is that a specific type of harm will occur under specific conditions. They concluded that aspartame does not pose a safety risk in the amounts that people consume it and confirmed the current acceptable daily intake is still appropriate.

• The categorization in Group 2B (possibly carcinogenic to humans) is based on limited evidence of carcinogenicity in humans and animals, and of limited mechanistic evidence on how carcinogenicity could occur.

IARC places substances in this category when it considers the evidence from studies in humans to be "limited" and/or the evidence from studies in animals to be "less than sufficient" to demonstrate a causal relationship between the agent and cancer. Other substances or factors in the same group as aspartame include traditional Asian pickled vegetables, Aloe vera extract and several chemicals used in dry-cleaning or by hairdressers. The strength of the evidence for a substance from Group 2B having to potential to cause cancer is lower than for groups 1 (carcinogenic to humans, including smoking, solar radiation, drinking alcohol) and 2A (probably carcinogenic to humans, including consuming red meat, night shift work). Classifying aspartame as a Group 2B carcinogen underscores the need for more research to clarify whether consuming aspartame poses a carcinogenic hazard.

• JEFCA confirmed that their previously established ADI of 0-40 mg/kg body weight is still appropriate.

They confirmed that it is safe for people to consume aspartame within these limits.² A standard can of artificially sweetened soda or soft drink usually contains around 200-300 mg of aspartame. An adult weighting 70 kg would need to drink around 9-14 cans daily in order to go over this recommended maximum limit.

Alan Reilly, Ex-Chief Executive, Food Safety Authority of Ireland, and Adjunct Professor at the Institute of Food and Health at University College Dublin explains: "Aspartame is an approved food additive and its safety has been evaluated by leading international agencies and scientific committees over many years. It has been found to be safe to use in foods. The most recent evaluation published today of its safety by the Joint Expert Committee on Food Additives, an international scientific expert committee that is administered jointly by the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO), have reconfirmed that it is safe to use in foods at the approved levels".

What do other authorities say?

• In 2013, the European Food Safety Authority (EFSA) concluded that aspartame and its breakdown products in the body (phenylalanine, aspartic acid and methanol) are safe for human consumption at current intake levels and that the current Acceptable Daily Intake (ADI) of 40 milligrams per kilogram of body weight per day is suitable for the general population.³ EFSA is currently re-evaluating the safety of two related food additives, aspartame-acesulfame and neotame, and as part of this re-evaluation they will consider new data on safety and dietary exposure to aspartame that has been generated since 2013.