Should You Be Worried About Aspartame?

Aspartame was recently classified as a "possible human carcinogen." We asked two nutrition experts to explain what this means—and whether we really need to eliminate it from our diets.
A glass of cola on a red background (Photo: iStock)

If you’ve read the news lately, you’re likely wondering: Should I be avoiding aspartame?

In July, the World Health Organization’s International Research Agency on Cancer announced that it had classified the zero-calorie artificial sweetener as a possible human carcinogen. (Several months earlier, the WHO also pointed to a potential link between long-term aspartame consumption and the risk of both type-2 diabetes and cardiovascular diseases.) But it’s not clear how we should respond to this news, especially since the U.S. Food and Drug Administration has issued a statement noting that it disagrees with this classification.

To find out whether the average person should rethink their aspartame consumption, we talked to Leanne De Souza-Kenney, who teaches in the Human Biology and University College Health Studies department at the University of Toronto, and Vasanti Malik, a faculty member at U of T’s Department of Nutritional Sciences who holds the Canada Research Chair in Nutrition and Chronic Disease Prevention.

What exactly is aspartame—and just how pervasive is it?

Aspartame, which is made from two amino acids (aspartic acid and phenylalanine), is both 200 times sweeter than sugar and cheaper than most other sugar alternatives, so it’s an appealing ingredient for manufacturers. According to the Calorie Control Council, an international association for the low- and reduced-calorie food and beverage industry, aspartame is estimated to be used in more than six thousand products around the world. These include sweeteners such as Equal and Sugar Twin, diet sodas and sugar-free gum.

Health Canada currently sets the acceptable daily intake (ADI) of aspartame at 40 mg per kg of body weight, an amount equivalent to over a dozen cans of diet soda. But you may not be getting all of your aspartame from obvious sources. De Souza-Kenney says you may be passively consuming artificial sweeteners in products you might not expect. For example, your mouthwash, cough drops, vitamin supplements and low-calorie yogurts may also have aspartame listed as an ingredient.

Will consuming aspartame increase my cancer risk?


Malik wants people to know that the WHO’s recent declaration wasn’t prompted by new information, and it doesn’t give us definitive answers. It’s simply a call for more research. The IRAC’s classification system is based on strength of evidence for risk, not strength of actual risk. “This classification that was given to aspartame is one above the lowest—meaning there isn't very strong evidence [for] at all,” Malik says.

For substances in the same category as aspartame, such as aloe vera extract and diesel fuel, there’s limited evidence of cancer risk in humans, and “less than sufficient” evidence from animal trials. In comparison, alcoholic beverages, sunshine and processed meat fall into the highest-certainty category, meaning that they’re classified as carcinogenic to humans.

Are there other health risks associated with aspartame that I should know about?

Like with cancer risk, the research on aspartame’s other health concerns is fairly inconclusive. Past research links artificial sweetener consumption to a heightened risk of heart disease, high blood pressure, diabetes and obesity, but Malik says these studies may not give us a true picture of risk because it’s not always clear that artificial sweeteners are actually causing those health conditions. (Sometimes, for example, people participating in a study might know they’re at risk for conditions like diabetes, which prompts them to choose artificial sweeteners.)

Although the evidence of harmful effects is inconclusive, De Souza-Kenney says that it’s growing. She says reliable sources have linked aspartame consumption with neurotoxicity (which can cause cognitive problems, limb weakness and other issues) and mood disorders, including higher levels of anxiety, depression and migraines. “I think there's enough evidence to paint a picture that your quality of life can be compromised, and that there are risks involved,” she adds.


Announcements like the WHO’s are meant to alert people to be mindful of what they’re putting into their bodies, says De Souza Kenney.

Should I still be consuming aspartame?

Health Canada says it will review the scientific data and take steps to protect Canadians if necessary, but it’s unclear when an update will be available. In the meantime, aspartame intake is a matter of personal choice, so we asked Malik and De Souza-Kenney for their best advice.

Should I swap aspartame out for sugar?

Ideally, no, Malik says: “We have pretty clear and consistent evidence that excess consumption of sugar, particularly in the form of liquid sugar, is adverse for health.” Instead, she emphasizes that the optimal goal is to wean yourself off of sweeteners—natural and artificial—altogether. If that’s not possible, she says you can continue using non-nutritive sweeteners like aspartame with the eventual goal of eliminating them from your diet, as long as you stay within the ADI limit for your body weight. (A 150-pound woman, for example, should consume no more than 6,000 mg of aspartame daily.)

In general, De Souza-Kenney suggests what’s most important is to focus on a diet that’s high in nutrients. It won’t help to fixate so much on sweeteners that you forget to consider what other nutrients you want to get out of each meal, such as fibre and protein. A high-fibre granola bar with aspartame might be more nutritious than a low-fibre, aspartame-free granola bar.


In other words, remember that aspartame is just one of many ingredients you’re consuming on a day-to-day basis, and it’s not worth vilifying—just worth paying attention to.


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