Updated Jul 14, 2023 - Health

Diet Coke's appeal fizzling as sweetener hit with cancer warning

Illustration of an aluminum can with a large question mark on it

Illustration: Natalie Peeples/Axios

Despite Diet Coke's cultish following, sales have been in decline over perceptions of its health risks.

Why it matters: A World Health Organization cancer agency on Thursday classified aspartame — a key sweetener — as possibly carcinogenic, though experts say that likely doesn't mean you need to quit Diet Coke.

Driving the news: Consumer concern about aspartame health warnings has already hurt Diet Coke sales.

  • The soda "has been in a long-term decline as loyal consumers age out of the product," Beverage Digest editor and publisher Duane Stanford told Axios.
  • Adding flavors and other attempts to recruit younger Diet Coke drinkers have failed.

Between the lines: The WHO's specialized cancer research arm — the International Agency for Research on Cancer (IARC) — issued the new warning on aspartame's risk level, adding it needs further research.

  • The IARC now considers aspartame a class 2B carcinogen, "possibly carcinogenic to humans," based on limited evidence, including animal studies.
  • Evidence was strongest — though still limited — for liver cancer in humans, said Mary Schubauer-Berigan, IARC classification branch head.
  • Other substances in the 2B category include pickled vegetables and aloe vera. (Coffee was, too, before being reduced to 3 in 2016.)

Meanwhile, the FDA said it "disagrees with IARC's conclusion" to classify aspartame as a possible carcinogen to humans.

Of note: The IARC only looks at whether something could cause cancer, not at what dose it's dangerous.

  • Another group — the Joint Food and Agriculture Organization/WHO Expert Committee on Food Additives (JECFA) — evaluates how much of an additive can be consumed without major risk.
  • JECFA didn't update their recommended daily intake of aspartame with the IARC's findings.

Reality check: A 150-pound person could drink 14 cans of Diet Coke in a day and still be within the JECFA's safe range, according to the math of Professor Tracy Crane, co-leader of the Cancer Control Research Program at Sylvester Comprehensive Cancer Center.

Diet Coke drinkers might not need to kick the can completely — but the new aspartame label could be a moment to assess how much artificial sugar and added sugar is in your diet.

  • "Occasional consumption of aspartame is… probably not going to be associated with a health risk for most individuals," said Dr. Francesco Branca, WHO director of nutrition and food safety.
  • Kevin Keane, interim CEO of American Beverage, which represents The Coca-Cola Company, told Axios: “Aspartame is safe... This strong conclusion reinforces the position of the FDA and food safety agencies from more than 90 countries.”

By the numbers: The amount of Diet Coke consumed during the first quarter of this year declined 6.5%, compared to a narrower 2.8% decline for the soft drink category, Stanford said.

  • And for the 12 months ending in March 2023, more than 1 in 4 adults said they were avoiding artificial sweeteners like aspartame in their diets, per a Circana/Health Attitudes & Behavioral Tracker.

But Diet Coke isn't Diet Coke without aspartame.

  • The fizzy, light, distinctively not-Coke flavor is "characterized in large part by aspartame," Stanford said.

Thought bubble: I'm not ready to give up my occasional keep-me-awake Diet Coke, and I have a feeling Tom Hanks isn't, either.

Go deeper: Possible health impacts of artificial sugar

Editor’s note: This story was updated to include a new statement from the FDA.

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