The Decades-Long Struggle to Figure Out Whether Aspartame Is Bad for You

For the first time ever, the artificial sweetener aspartame is set to be listed as “possibly carcinogenic to humans” by a health authority, report Jennifer Rigby and Richa Naidu for Reuters in an exclusive story. Two inside sources told the wire service that the World Health Organization (WHO) body that studies cancer, the International Agency for Research on Cancer (IARC), will publish its ruling on July 14. But maybe don’t put down your Coke Zero just yet.

The IARC’s job is to consider all publicly available evidence on a substance and rule on whether or not it might be a carcinogen in any quantity. “It has four different levels of classification—carcinogenic, probably carcinogenic, possibly carcinogenic and not classifiable,” Reuters reports. “The levels are based on the strength of the evidence, rather than how dangerous a substance is.” For instance, processed meat, sunshine and asbestos are all carcinogenic, according to this system, while red meat and working overnight are probably carcinogenic.

The category aspartame would be part of, ‘possibly carcinogenic’, “is a large category which includes things such as aloe vera extract and bracken fern, but also diesel fuel and HIV,” Gunter Kuhnle, a nutritional biochemist and professor at the University of Reading, wrote in a comment published by the Science Media Center, a London-based non-profit devoted to independent science communication.

Aspartame, a mainstay of diet beverages for decades, is coming under new scrutiny. The World Health Organization recently called two meetings to reevaluate its safety and it's possible increased cancer risk. https://t.co/RfZFv6ZEqo

— The Washington Post (@washingtonpost) June 23, 2023

Kuhnle and other scientists quoted by the organization caution against drawing conclusions before the ruling is published. And another WHO body, the Joint WHO and Food and Agriculture Organization's Expert Committee on Food Additives (JEFCA), will be publishing its own risk assessment on aspartame the same day. Researchers at JEFCA study food additives specifically for their health risks and have ruled many times that aspartame at reasonable quantities is safe for human consumption, writes Live Science’s Nicoletta Lanese. A U.S. Department of Human and Health Services letter dated last August suggests that the dual reports have the potential to be confusing, since JEFCA also uses further sources of evidence, including proprietary information, to draw its conclusions.

“An IARC review of aspartame, by comparison, would be incomplete, and its conclusions could be confusing to consumers,” Mara Burr, director of the HHS’s Multilateral Relations Office, wrote in the August letter. “WHO should only issue public health recommendations based on an assessment of all available data.”

The U.S. Food and Drug Administration’s current stance on aspartame remains what it was when rumors started to swirl online about the substance in the 1990s: Aspartame, in the quantities you are likely to consume it, is safe for humans. “Since the last approved use in 1996, the FDA has continued monitoring the scientific literature for new information on aspartame,” reads the agency’s webpage about the artificial sweetener. “We stay abreast of published literature and the current level of consumer exposure and participate in international scientific and standard-setting activities related to food ingredient safety.”

It’s possible that new evidence will change our view of this substance, which the FDA notes is one of the most-studied food additives. But the new questions about aspartame also bring to mind a hoax that provides a glimpse into what the early days of the internet were like, and how some things never really change.

Patented in 1970 as Nutrasweet, one of the names it’s still sold under, aspartame was the subject of a panic in the 1990s that included health threats beyond cancer. Persistent rumors about aspartame’s links to seemingly every condition under the sun go back to what’s known as the “Nancy Markle” allegations: a letter that linked “ASPARTAME DISEASE!” to fibromyalgia, among other things, and said MS was methanol toxicity rather than a pernicious autoimmune disease.

It was supposedly written by Nancy Markle, who had recently “spent several days lecturing at the WORLD ENVIRONMENTAL CONFERENCE” on aspartame. A Google search of “world environmental conference” is dominated by results related to Markle’s aspartame conference, which supposedly happened in 1995.

The truth: Nancy Markle never existed. The letter was written by an aspartame truther named Betty Martini, writes librarian Paul S. Piper for Western Washington University. Martini herself died earlier this year, but the letter’s use of all-caps writing and conversational (read: poorly punctuated) tone to convey “scientific” information probably looks familiar for anyone who's spent any time on the internet.

The letter made its way around the internet for years and is still around as chain mail. It's the canonical example of an internet hoax, and it spread quickly. In a very different letter printed in The Lancet, one of medicine’s foremost journals, in 1999, researchers wrote that they had found over 6,000 websites mentioning aspartame, with many saying it was the cause of “multiple sclerosis, lupus erythematosus, Gulf War Syndrome, chronic fatigue syndrome, brain tumors and diabetes mellitus, among many others.”

The web was relatively small back then, and the aspartame hoax grew with it, as people tried to navigate this new technology. Virtually none of those 6,000 websites offered sound evidence rather than anecdotes, the Lancet researchers said. Some attempted to sound more scientific, by citing the chemical products created when our bodies digest aspartame: methanol and phenylalanine. That part is true. Aspartame does break down into methanol and phenylalanine. But that shouldn't be scary.

“Over time,” writes PBS in a story about aspartame misinformation, “methanol can produce the known carcinogen formaldehyde. While this might seem scary, [a video released by the American Chemical Society] claims that the body actually produces and uses 1,000 times more formaldehyde than you could consume through aspartame. After helping to make important proteins, formaldehyde gets turned into formic acid and exits the body through urine.” The other chemical, phenylalanine, isn’t linked to depression, they write. And there is eight times as much of it in milk as in aspartame.

In 2013, academic Adam Burgess wrote that the public uncertainty created as a result of the aspartame myths is still an issue “in the context of the importance of promoting sugar-free alternatives, in a world where challenging obesity is a high priority.”

Out of all of the substances in our diet, why this one? It probably all goes back to the perception that “chemicals” are bad for you, whereas sugar, an honest, natural sweetener, must be good.

These debates continue even as misinformation has only become even more of a problem online in the nearly 30 years since an early letter spread across the nascent web.

Kat Eschner | | READ MORE

Kat Eschner is a freelance science and culture journalist based in Toronto.