WHO says aspartame could be a cancer risk. Experts say more research is needed

After weeks of speculation, the World Health Organization (WHO) deemed aspartame, a popular sweetener alternative to sugar, as "possibly carcinogenic to humans" on Thursday. 

In a summarized report published in The Lancet Oncology, researchers with WHO and the Food and Agriculture Organization of the United Nations (FAO) reviewed several trials and studies involving humans and animals ingesting aspartame. They found "limited" evidence for liver cancer risks in humans. 

While a "consistent association" between aspartame consumption and a specific cancer type was not observed, experts say the change in designation should lead to further research into its health impacts. 

"We're not advising companies to withdraw products, nor we are advising consumers to stop consuming altogether. We [are] just advising for a bit of moderation," Francesco Branca, director of the department of nutrition and food safety for WHO, told a news conference Wednesday.

"This is really more a call to the research community to try to better clarify and understand the carcinogenic hazard that may or may not be posed by aspartame consumption," added Mary Schubauer-Berigan, the head of the monographs program at the International Agency for Research on Cancer (IARC), also part of WHO.

The designation was made official Thursday, more than a month after researchers met to discuss a new possible classification for aspartame. Full reports on the UN researchers' assessments are expected to follow in the coming months. 

According to the government of Canada, aspartame is a low-calorie artificial sweetener that has been used as a food additive here since 1981. It's used in foods and beverages like pop, breakfast cereals and chewing gum and is also used as an alternative to sugar in caffeinated drinks.

It's currently used in more than 90 countries, according to the federal government, including the United States, European nations, Australia and New Zealand.

The federal government says food additives like aspartame are subject to "rigorous" controls under its Food and Drugs Act and Regulations. According to its website, officials evaluated an "extensive" array of toxicological tests in laboratory animals and examined the results of a number of clinical studies in humans. 

"There is no evidence to suggest that the consumption of foods containing this sweetener, according to the provisions of the Food and Drug Regulations and as part of a well-balanced diet, would pose a health hazard to consumers," Health Canada's website reads.

Scientists with the Food Directorate of Health Canada established the acceptable daily intake (ADI) of aspartame as 40 milligrams per kilogram of body weight per day. That's the same amount as what the FAO and WHO joint expert committee on food additives, who weighed in on the new classification, recommends.

In response to the WHO's change in designation, Health Canada said in an email to CBC News it will review the initial report and the full assessments once released. 

"At that time, the department will determine whether action is needed for aspartame in Canada based on the scientific data," said a Health Canada spokesperson. 

"If the new research indicates that aspartame or any other food additive is unsafe for its permitted use, Health Canada will take action to protect Canadians, which could include reducing its maximum level of use, further restricting which foods it may be used in or no longer permitting it to be used as a food additive."