- Sources tell Reuters that the World Health Organization is set to declare aspartame a possible human carcinogen.
- This means it may cause cancer.
- It’s unclear how much aspartame is a potential issue for people consuming it.
Artificial sweeteners haven’t had the best reputation lately—they’ve recently been linked to a higher risk of heart issues and leaky gut syndrome, among other things. But there’s one type of artificial sweetener that’s repeatedly been associated with health issues: aspartame.
Now, a new report says that the World Health Organization (WHO) is set to declare aspartame as “possibly carcinogenic to humans” in 2023 (meaning, it may cause cancer).
Sources told Reuters that aspartame will be labelled as possibly carcinogenic to humans for the first time, by the International Agency for Research on Cancer (IARC), an arm of the WHO.
The classification is designed to determine whether something is a potential hazard based on available evidence. Worth noting: It doesn’t determine how much of a product a person can safely have.
Currently, the Joint WHO and Food and Agriculture Organization's Expert Committee on Food Additives (JECFA) says publicly that aspartame is safe to have within reasonable amounts.
Reuters notes that an adult who weighs 60kg would have to drink between 12 and 36 cans of diet soda to exceed those. Those recommendations might change soon.
The IARC has four classifications: carcinogenic (meaning, something is known to cause cancer), probably carcinogenic (something likely causes cancer), possibly carcinogenic (something has been linked to cancer), and not classifiable (researchers don’t have enough evidence to determine whether something causes cancer).
The report comes on the heels of the WHO warning that using artificial sweeteners for weight control could potentially lead to health issues.
But what is aspartame, exactly, and why might it cause cancer? Nutritionists explain.
What is aspartame?
Aspartame is a non-nutritive artificial sweetener that’s 200 times sweeter than sugar, according to Food Standards Australia and New Zealand. It’s sold under brand names like NutraSweet and Equal, and it’s been widely used since the early 1980s.
“Aspartame is a combination of two amino acids—phenylalanine, and aspartic acid,” says dietitian Jessica Cording. “It’s very, very sweet.”
“When consumed, aspartame is broken down in the gut into its original components: phenylalanine, aspartic acid, and methanol,” says dietitian Scott Keatley.
“The phenylalanine and aspartic acid are absorbed into the body while the methanol is eventually converted into CO2 and water.”
Aspartame isn’t heat stable and it loses its sweetness when it’s heated, so it usually isn’t used in baked goods.
Common products that contain aspartame
- Zero sugar and diet sodas, including Diet Coke
- Diet drink mixes
- Sugar-free gum
- Certain non-sugar sweeteners like Nutrasweet and Equal
What is aspartame used for?
Aspartame is generally “used as a sweetener in commercial products or for individual use,” says dietitian Beth Warren.
“Aspartame is primarily used as a sugar substitute in many diet or sugar-free products to provide sweetness without adding significant calories,” Keatley says. Because it’s not heat stable, it usually shows up in diet sodas or low-calorie desserts, he says.
It also can show up in some chewing gums, Cording says.
“Aspartame is typically found in packaged foods that are meant to be sugar free or low calorie,” she adds.
Why might aspartame be bad for you?
Some studies in rats have suggested that aspartame may increase the risk of certain blood-related cancers—specifically leukaemia and lymphoma. However, later reviews of those studies called the findings into question.
But another review of the findings published in 2021 confirmed the original findings, creating a lot of confusion. Studies of groups of people who use aspartame have had inconsistent results when it comes to the link between aspartame and cancer.
Several major safety organisations have said that aspartame is safe to use. Food Standards Australia and New Zealand says "all scientific evidence to date supports the safety of aspartame for use as a sweetener, however re-evaluation work is proposed."
The European Food Safety Authority (EFSA) said studies didn't suggest a link with cancer but has recently updated its website to say that its scientists are “currently re-evaluating the safety” of aspartame.
“The claim that aspartame could potentially be carcinogenic—meaning it could increase the risk of cancer—is a contentious issue,” Keatley says.
“The body metabolises aspartame into phenylalanine, aspartic acid, and methanol, the last of which can be toxic in high amounts. Yet, the levels from aspartame consumption are generally considered too low to cause harm.”
Keatley stresses that the IARC doesn’t take dose into consideration when making its recommendations. In previous other studies that “there is not an increase in incidences of cancer beyond baseline when using aspartame,” he says.
But Cording says that “there is some concern from animal studies, and human studies in the last year or two have highlighted a potential harmful effect.” It’s just that none of it is conclusive, she says.
It’s important to note that people with a rare genetic disorder called phenylketonuria (PKU) can’t have phenylalanine, an amino acid found in aspartame, because their bodies can’t break it down, the American Cancer Society explains. Other than that, the sweetener hasn’t been definitively linked to any health problems.
Aspartame isn’t the only artificial sweetener under fire lately
Research published in March linked the sweetener erythritol to a higher risk of experiencing a range of cardiovascular issues, including blood clots, stroke, heart attack, and death.
A recent study published in the Journal of Toxicology and Environmental Health, Part B found that sucralose and sucralose-6-acetate—a form of sucralose that occurs after your body breaks down the sweetener—is genotoxic, which means it can damage DNA.
It also found that sucralose can damage the walls of the gut, leading to leaky gut syndrome, (a condition where your gut “leaks” elements that would normally end up in your poo into your bloodstream.)
Another study published in April 2022 found that artificial sweeteners may interfere with your liver’s ability to effectively detox your body.
Is aspartame dangerous?
Experts stop short of saying you should avoid the sweetener entirely—but they do encourage people to limit it.
“Generally, my advice would be to moderate the consumption of aspartame and other artificial sweeteners,” Keatley says.
“While most research has concluded that consuming aspartame in moderation is safe for the general population, it’s still important to maintain a balanced diet and not to rely heavily on artificially sweetened products, as they can potentially lead to overconsumption due to their low-calorie illusion.”
Cording also recommends that her patients limit their use of aspartame and other artificial sweeteners.
“When it comes to sugar and other sweeteners to use, I tell people to use whatever is the most satisfying in the least amount,” she says.
Cording says she also tends to steer patients who are interested in using artificial sweeteners toward allulose. “It’s derived from corn, figs, and pears,” she says. “It’s a naturally-occurring sugar.”
But Cording stresses that there’s a lot we still don’t know about artificial sweeteners, including aspartame. “We need more research on all of them,” she says.
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