About eight years ago, in response to customer concerns about possible health risks associated with the artificial sweetener aspartame, PepsiCo decided to remove the ingredient from its popular diet soda.
Sales flopped. A year later, aspartame was back in Diet Pepsi.
Today, the top three ingredients listed in the tiny print on the backs of cans and bottles of Diet Pepsi — and on its competitor Diet Coke — are water, caramel color and aspartame.
A trip through the grocery store reveals the ingredient on the labels of not only diet sodas but also diet teas, sugar-free gums, sugar-free energy drinks and diet lemonade drink mix. By some estimates, thousands of products contain aspartame.
The use of aspartame, which is often known by the brand name Equal, in food and beverage products has long been scrutinized. The latest iteration came on Thursday, when an agency of the World Health Organization declared that aspartame could possibly cause cancer and encouraged people who consume a significant number of beverages with aspartame to switch to water or other unsweetened drinks.
But even with the emergence of many new artificial sweeteners, as well as those that are plant- and fruit-based, Big Food just can’t quit aspartame, and analysts don’t expect it to this time. That’s because the ingredient is one of the least expensive sugar alternatives to use, it works especially well in beverages and mixes, and people like the way it tastes.
There was also pushback about the urgency of the W.H.O.’s announcement. In a quick rebuke, the U.S. Food and Drug Administration said it disagreed with the findings, reiterating its stance that aspartame is safe. And a second W.H.O. committee said a 150-pound person would need to drink more than a dozen cans of Diet Coke a day to exceed the safe threshold for the sweetener.
“The big beverage companies have been doing contingency planning for months, experimenting with different sweeteners, with a goal of having the taste and quality of the diet beverages being as consistent as possible with existing products,” said Garrett Nelson, who covers the beverage industry at CFRA Research. But they are not likely to change the recipe unless they see a significant drop in consumer demand based on the W.H.O. report, he said.
“If consumers really stop buying Diet Coke because of this report, if sales start to suffer, it might be time to go to Plan B,” Mr. Nelson said.
Coca-Cola referred questions to the American Beverage Association, the lobbying arm for the industry. “Aspartame is safe,” Kevin Keane, the interim president of the organization, said in a statement.
PepsiCo did not respond to questions for comment, but in an interview with Bloomberg Markets that aired on Thursday, Hugh F. Johnston, the chief financial officer of PepsiCo, said he did not expect a big consumer reaction.
“I do believe that, in fact, this is not going to be a significant issue with consumers based on just the preponderance of evidence that suggests aspartame is safe,” Mr. Johnston said.
The assessment of the W.H.O. agency adds to consumer confusion around aspartame, but it is also the latest in a recent spate of research focusing on the potential risks and questioning the true benefits of artificial sweeteners. Just a few weeks ago, the W.H.O. advised against using artificial sweeteners for weight control, saying a review of studies did not show long-term benefit in reducing body fat in children or adults. The review also suggested that the sweeteners were tied to an increased risk of Type 2 diabetes and cardiovascular diseases.
This year, researchers at North Carolina State University and the University of North Carolina at Chapel Hill released a study that found a chemical formed after digesting another sweetener, sucralose, breaks up DNA and may contribute to health problems.
For years, food and beverage companies and regulators have typically denounced research that raises questions about artificial sweeteners, broadly arguing that the studies were flawed or inconclusive or that the health risks were minuscule.
“A substantial body of scientific evidence shows that low- and no-calorie sweeteners provide effective and safe options to reduce sugar and calorie consumption,” Robert Rankin, president of the Calorie Control Council, the lobbying association for manufacturers and suppliers of nearly two dozen alternative sweeteners, said in an emailed statement on Thursday.
Indeed, most food and beverage companies that use aspartame are reluctant to switch partly because aspartame is less expensive than other alternatives and is 200 times as sweet as sugar, meaning a little goes a very long way.
“One of the benefits of aspartame is that it’s been made for so long that manufacturers have really refined the costs and processing of it so well and they get a superior product,” said Glenn Roy, an adjunct organic chemistry professor at Vassar College who spent more than three decades working at food companies, including NutraSweet, General Foods and PepsiCo.
On top of that, the F.D.A. approved aspartame in 1974, giving companies decades of data and information on what aspartame can and cannot do in products. For instance, it can enhance and extend certain fruit flavors, like cherry and orange, making it a preferred sweetener for beverages and chewing gum. But when heated, aspartame loses its sweetness, making it less desirable for baked or cooked products.
Food and beverage companies are releasing new no- or low-sugar products in response to consumer demand, but many are being made with newer sweeteners, or a blend of sweeteners. Each new product undergoes a litany of sensory and flavor tests before it is released.
But for products that have been around for decades, like diet sodas, loyal customers are accustomed to a specific taste, and they could be turned off by changes in ingredients, scientists warn.