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Will diet soda, yogurt, and cereal disappear from stores?

What the WHO’s aspartame warnings mean for you.

Grocery store aisle with shelves full of food products.
The grocery shelves are about to get that much more daunting. On July 14, the World Health Organization classified aspartame as “possibly carcinogenic to humans.” It’s in tons of food and beverages.
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Whizy Kim is a reporter covering how the world's wealthiest people wield influence, including the policies and cultural norms they help forge. Before joining Vox, she was a senior writer at Refinery29.

Diet soda. Chewing gum. Yogurt. Cereal. No, this isn’t someone’s grocery list — these are everyday consumer products that can contain the popular artificial sweetener aspartame.

This week, the World Health Organization’s International Agency for Research on Cancer (IARC) declared aspartame as “possibly carcinogenic.” Another WHO committee, the Joint FAO/WHO Expert Committee on Food Additives (JECFA), independently assessed the ingredient, too, but maintained its existing recommendation — suggesting not that people cut the substance entirely out of their diets but that they limit their daily aspartame consumption to about 40 mg per kilogram (or about 2.2 pounds) of body weight. Diet soda contains about 200 mg of aspartame per 12-ounce can. By that measure, an adult weighing 60 kg, or roughly 132 pounds, would need to drink about 12 cans of diet soda a day to exceed the JECFA’s recommendation, assuming they had nothing else containing aspartame.

Making matters more confounding, the Food and Drug Administration had yet another take. It told Vox in an email that it had reviewed the information used in WHO’s assessment and “identified significant shortcomings” in the studies the agency relied on. “Aspartame is one of the most studied food additives in the human food supply,” the agency added.

All this creates a fair amount of confusion for consumers, leaving many of us with questions about whether we should cut out the thousands of products using the sweetener, worry about what we’ve already consumed, or do nothing at all. Vox sought answers to some of the questions you might have right now.

What is aspartame?

Aspartame is an artificial sweetener first discovered in 1965, though it really exploded in popularity in the US in the 1980s, after its approval by the FDA, replacing more than a billion pounds of sugar throughout the decade. As awareness and concern over excessive sugar consumption grew and rates of Type 2 diabetes and obesity in the US rose, artificial sweeteners became a popular low-calorie sugar substitute in food and drinks, with consumers clamoring for “diet” versions of popular products. Aspartame was hardly the first artificial sweetener; cyclamate and saccharin preceded its use, but they were both eventually banned for cancer concerns. Today, over 5,000 products sold in the US contain aspartame.

What do the WHO’s findings even mean?

You’d be forgiven for thinking that the WHO is saying aspartame might be totally fine for consumption, as long as you don’t overdo it. The fact that JECFA did not change its recommended daily intake also feels like another point for Team No Big Deal, too.

“When you say it’s a ‘possible carcinogen,’ it’s easy for a consumer to gravitate toward the ‘possible’ part and say, ‘Okay, well, it’s not an immediate threat,” says Brian Ronholm, director of food policy at Consumer Reports, which publishes product tests and investigative journalism, and spearheads consumer advocacy campaigns.

The big takeaway from the WHO’s conclusion, however, is that we just don’t know enough about aspartame’s cancer risk in humans. IARC relied on just three available studies looking into the carcinogenic effect of aspartame in humans that showed possible links to liver cancer.

The IARC uses four classification levels when it comes to agents: Substances in Group 1 are classified as cancer-causing in humans because sufficient evidence exists that they are indeed carcinogens; Group 2A, probably causes cancer; Group 2B, possibly causes cancer; and Group 3 encompasses substances unclassifiable as a cancer risk. Tobacco, sulfur mustard (also known as mustard gas), and asbestos are all Group 1. Aspartame is in Group 2B. Other Group 2B agents include aloe vera, talc-based body powder (which can contain asbestos), nickel, and safrole, a chemical in ingredients used to add flavor to root beer. The FDA banned safrole in food in 1960.

Here’s what’s really important for consumers: Nothing happens automatically based on the WHO’s assessment; it’s up to regulators, companies, and consumers to decide how to respond. But the assessment certainly should raise eyebrows, especially because the WHO’s cancer research arm is a trusted authority. Experts told Vox that a US ban on aspartame isn’t likely, at least not anytime soon, and food and beverage companies aren’t likely to swiftly remove their products from the shelves.

That means, of course, that the choice to continue drinking Diet Coke, chewing Trident Gum, eating sugar-free Jell-O, or consuming one of the many other foods and drinks that use aspartame as a sugar substitute, is left up to individual consumers. Consumer protection groups, meanwhile, have been recommending people avoid aspartame, and the American Cancer Society is advising caution, too.

“The science is still evolving, but we recommend people use today’s report by IARC as a time to reflect on their use of aspartame, but also an opportunity to review their overall dietary intake, including processed meat and alcohol, known carcinogens associated with increased risk of cancer,” Dr. William Dahut, the American Cancer Society’s chief scientific officer, said in a press release. He added that the organization “supports the IARC’s call for more research of aspartame and other artificial sweeteners.”

Should we avoid all aspartame?

If only there were a clear-cut answer.

“From a consumer perspective, they’ll probably find the mixed messaging confusing and frustrating,” says Ronholm. “Those who already had concerns and serious questions about aspartame, they’ll think more about sharply limiting their consumption. But there’s also going to be a segment that will continue to consume these beverages and thinking that ‘Well, nothing’s happened to me yet.’”

Consumer advocates are urging that people be aware of just how many products can contain aspartame. Not just soda, but low- or no-sugar candies, breakfast cereals, instant coffee, gelatin products, and syrups may all use the sweetener.

The Center for Science in the Public Interest (CSPI), a consumer watchdog and advocacy group, has been recommending for a long time that consumers avoid aspartame due to its possible links to cancer. “This should be very concerning for consumers, for industry, and for regulators,” says Thomas Galligan, a principal scientist for food additives and supplements for the organization.

Galligan urges consumers to avoid it. “But I say that with a really important caveat — that consumers should not switch out aspartame for sugar. Regular sugary-sweet soda poses a greater health risk to consumers than aspartame and other non-nutritive sweeteners.” He recommends using or looking for products that contain the natural sweetener stevia instead. Better yet, drink water.

Will my favorite soda disappear from the shelves?

Many companies have been surprisingly quiet in their response to the news. Yesterday, PepsiCo’s chief financial officer told Reuters that the company had no plans to change its products at this point. The company uses aspartame in Pepsi Zero Sugar, but not in Diet Pepsi.

“Banning these products is not going to be happening anytime soon,” says Ronholm. The CSPI is urging companies to take IARC’s assessment seriously and reformulate their products — or at least increase the availability of unsweetened products. Both Galligan and Ronholm were skeptical that they would do so. “I can’t envision them reformulating any of their products as a result of this announcement, unless there’s some significant consumer backlash that results in a sharp decline in demand,” Ronholm says. The fact that the WHO’s messaging is probably confusing to consumers and the FDA disagrees with its findings make it unlikely that companies will be motivated to change their products.

The food and beverage industry, well aware that the IARC was looking into aspartame, has been on the defensive for a while. Industry representatives “actually met with the FDA [in] the middle of last year,” says Galligan.

“I would say that the beverage industry is going to continue on those tactics, trying to discredit [and] undercut this really important finding,” Galligan says.

Will the FDA do anything?

The FDA has made clear that it doesn’t see eye to eye with IARC. But that doesn’t necessarily mean the US agency won’t do anything, especially if public and political pressure mounts. Galligan cites a federal statute called the Delaney Clause. Part of the Food Additives Amendment of 1958, which empowered the FDA to require all companies to test new food additives before products hit the market, the Delaney Clause “basically expressly prohibits any chemical that’s been shown to cause cancer from being used,” says Galligan. While in other cases the FDA can rate food additives as safe at certain amounts, this clause imposes a strict zero-risk policy on additives shown to cause cancer in animals. According to Galligan, the clause could trigger here. But he added that “while [the FDA] have the authority to regularly reevaluate food additives that have been approved for use, they really rarely do.”

“We believe that Congress made it very clear when they passed the food additive amendment in 1958 that no amount of possible carcinogens, probable carcinogens, et cetera, are allowed in our food,” he says.

As my colleague Keren Landman has explained, the FDA’s approval of aspartame has a checkered history. Its use was initially denied, then approved in 1981 despite concerns that it might cause brain tumors. Over the past few decades, many scientists have warned of its potential cancer risk — those who disputed these concerns were often backed by groups representing the food and beverage industry.

“You look at the uncertain science surrounding it, you look at the dubious evaluation process that was associated with its original approval — based on that, Consumer Reports has long urged caution in consuming aspartame and will continue to do so,” Ronholm says.

He continued that even with other chemicals and additives, the FDA has “typically been hesitant” to address issues. A Politico investigation last year painted a picture of a sluggish, dysfunctional agency, particularly when it came to food safety, citing that its food branch had “a deep-seated culture of avoiding hard decisions and a near-paralyzing fear of picking serious fights with the food industry.”

It’s also worth noting that the FDA’s stance on aspartame is echoed by regulatory bodies in other countries. Over 90 countries currently consider it safe to use in food.

Can anything make a difference to companies still planning to use aspartame in their products?

Experts told Vox that consumer backlash could be the quickest way to get food and beverage companies to reformulate or provide aspartame-less alternatives. Take the case of talc, a mineral that can sometimes contain asbestos. In 2006, IARC classified talc with asbestos as a Group 2B carcinogen, the same as it has now done with aspartame. It hasn’t been banned by US regulators, but an onslaught of lawsuits from consumers eventually led to Johnson & Johnson voluntarily stopping sales of their talc-based baby powder, first in the US and Canada but now worldwide. Many makeup brands followed, and some now even tout their talc-free formulations as a selling point.

It’s also technically possible for individual states to get involved. California just passed a bill banning five “toxic food chemicals,” including Red Dye No. 3, which the FDA banned in cosmetics decades ago but not in food. Consumer Reports was a co-sponsor of this bill. “One of the things that resonated with the California bill is [that] these were five chemicals that were already banned elsewhere in the world,” Ronholm says. “And oh, by the way, the industry was able to find alternatives to continue making these products and sell them overseas.” Ronholm says it’s possible a similar thing could happen here, though he’s not aware of anything in the works yet.

“If other states were interested in this issue and wanted to protect their citizens from aspartame, then seemingly that avenue for progress is available to them,” says Galligan.

In some cases, a good old-fashioned lawsuit can compel companies to stop sales or reformulate products. Glyphosate, a pesticide, is in IARC’s Group 2A classification — a “probable carcinogen.” The compound is banned in several countries, including Germany, Austria, Thailand, and Saudi Arabia, but not in the US. The Environmental Protection Agency has deemed it “not likely to be carcinogenic to humans.” But Bayer, which uses glyphosate in its weed killer Roundup, was ordered to pay $10 billion to settle thousands of lawsuits claiming that glyphosate causes cancer. The company is pulling Roundup from shelves this year.

Similarly, in 2015 the IARC classified processed meat — like bacon and hot dogs — as a Group 1 carcinogen. In 2016, the CSPI petitioned the USDA to require warning labels on processed meat. It was denied. In the immediate aftermath of the IARC report, sales of bacon and sausage plummeted in the UK. In the US, however, processed meat sales remain strong.

Unfortunately, the nuance around IARC’s assessment of aspartame, and the fact that regulatory bodies like the FDA disagree, will likely continue to mean frustration and confusion for consumers. As for whether we change our consumption — we’re on our own there.

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