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. 

What is aspartame anyway, and what is it used for?

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.

WATCH | How sweeteners could lead to weight gain: 

Sweeteners and weight gain

6 years ago

Duration 2:09

A new review suggests that sweetener benefits are hard to digest

How does Canada currently regulate aspartame? 

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."

Should you change your consumption habits? 

The IARC has a total of four classifications ranking carcinogenic hazards to humans — carcinogenic to humans, probably carcinogenic to humans, possibly carcinogenic to humans and not classifiable.

Vasanti Malik, an assistant professor teaching nutritional sciences at the University of Toronto, said the UN designation for aspartame doesn't change her understanding of the current literature. She compared the designation to that of red meat, which is deemed a "probable carcinogen."

"We really need strong research that can look at the different sweeteners independently over time, and that's not how the studies were done," said Malik.

Under Health Canada's current guidance, the average adult needs to drink about 14 cans of Diet Coke to hit their acceptable daily intake of aspartame, Malik said. While that may be "crazy" to visualize, she said people should keep track of where else aspartame may appear in their diets, such as yogurt and desserts.

"We know we want to cut sugar down in the diet and artificial sweeteners are part of that," she said.

Consumers should use sweeteners like aspartame mostly as an interim alternative to weaning off sugar, said David Ma, a human health and nutritional sciences professor at the University of Guelph in Ontario.

While aspartame usually appears in "small" and "acceptable" amounts, he said people should still seek healthier alternatives. 

"The simple message is that there's not too much to worry about," said Ma. "If you are [worried], there are alternatives, drink more water or other healthy beverages."