Popular artificial sweetener aspartame labeled as a possible carcinogen by the WHO

The World Health Organization (WHO) has labeled the popular artificial sweetener aspartame as “possibly carcinogenic to humans” this July, according to an exclusive report by Reuters, which cited unnamed sources from WHO.

Aspartame is one of the most frequently used artificial sweeteners, having been sold under brand names like Equal and NutraSweet since the 1980s, according to the American Cancer Society. It also resides in several processed foods and beverages like certain gums, gelatins, sodas, and cold cereals—but tends not to be found in baked goods as aspartame loses its sweetness when heated, according to the Food and Drug Administration (FDA).^[][]

The FDA first approved aspartame as a sweetener in 1974, following scientific evidence that supported it was safe for human consumption, according to the agency. The FDA has re-reviewed aspartame’s safety several times since then and calls the sweetener “one of the most studied food additives in the human food supply.”^[]

The agency most recently reviewed aspartame’s safety profile in 2021, after a 2020 publication by Ramazzini Institute scientists linked aspartame to tumors in rats. This publication was first reviewed by the European Food Safety Authority (EFSA), which concluded that “no valid conclusion” could be derived from the study. The FDA supported the EFSA’s statement, keeping aspartame’s approval as it was.^[]

In the study, European researchers found that artificial sweeteners were associated with increased cancer risks among humans, adding to existing concerns about aspartame’s safety. The researchers studied a variety of sweeteners but found that aspartame was one of two sweeteners most associated with these risks. The other sweetener was acesulfame-K, which along with aspartame and sucralose is one of the most frequently consumed artificial sweeteners, according to the researchers. They concluded that the findings provided “novel insights for the EFSA and other health agencies to reevaluate food additive sweeteners.^[]

While the new research emphasizes the need for this re-evaluation, others suggest that labeling aspartame as a potential carcinogen could be a rash decision due to the plethora of research supporting its safety throughout the years. In the past, IARC decisions have faced criticism for sparking needless alarm,” according to Reuters. Among other problems with the ruling, IARC bases its decisions based on the “strength of evidence” supporting the classification, not “how dangerous a substance is,” according to Reuters. For example, if aspartame is expected to be classified as “possibly carcinogenic,” which is the lowest level of classification other than “not classifiable.” More problematic rulings include: “probably carcinogenic” or “carcinogenic.” A definite ruling by IARC would affirm the “probably” classification but would not infer that aspartame was probably or definitely carcinogenic.^[]

Christyna Johnson, RDN, LD, a registered dietitian at Encouraging Nutrition in Dallas, Texas, says that in the current state of things, she encourages clients to lean into bodily cues to assess how sweeteners are impacting them.

Questions such as: “Do you feel energized? Pleasant? Sluggish? Nauseous? Uncomfortable? Neutral?...can help someone notice when they are having more sugar than what may be helpful,” Johnson says. 

She adds that this can be, at times, tricky with artificials sweeteners, as the brain interprets these products differently than it does natural sugars or sucrose.

“Unfortunately, the body doesn't respond the same to artificial sweeteners as it does to sucrose, meaning that our brain uses receptors to regulate how much sugar we intake,” says Johnson. “Artificial sweeteners don’t react with those receptors, so it can be more difficult to feel satisfied after eating something with artificial sweeteners.”

For those nervous about their intake, she advises starting conversations with doctors about use. To best steward their health, people may also benefit from adhering to recommended dosages and looking to the WHO for any new announcements.