Aspartame, the artificial sweetener found in everything from diet drinks, yogurt, ice cream and breakfast cereals to medicines, toothpastes and instant coffee, has been determined by the World Health Organization to be “possibly carcinogenic.”

Citing the results of two new assessments of the health impact of the popular artificial sweetener, the WHO said that it has “limited evidence” that aspartame can cause cancer in humans. The International Agency for Research on Cancer’s report designated the sweetener as possibly carcinogenic. Another assessment, from the Joint FAO/WHO Expert Committee on Food Additives, or JECFA, found that at the current amounts commonly used by consumers, the safety of aspartame isn’t a major concern.

Despite the findings, “potential effects have been described that need to be investigated by more and better studies,” Francesco Branca, director of the WHO’s Department of Nutrition and Food Safety, said in a statement.

In a press conference from the WHO’s headquarters in Geneva, Branca urged consumers to look for products “without sugar or sweeteners.” As an alternative to the many sugar-sweetened and diet drinks on the global market, Branca said, “drink water instead.”

Sweeter Than Sugar

A chemical-based sweetener that is hundreds of times sweeter than sugar, aspartame is packaged and sold under names such as Equal. The US Food and Drug Administration approved aspartame in certain products in 1974, issuing a safety finding in 1981 and approving it as a general-purpose sweetener in 1996.

“Aspartame being labeled by IARC as ‘possibly carcinogenic to humans’ does not mean that aspartame is actually linked to cancer,” the FDA said in a statement. “The FDA disagrees with IARC’s conclusion that these studies support classifying aspartame as a possible carcinogen to humans.”

The food and beverage industry had been expecting the new designation from the WHO. Industry trade groups and experts from the science community responded to the announcement with statements criticizing the limited evidence of the IARC study, and reiterating earlier studies that have determined aspartame to be safe.

“There is a broad consensus in the scientific and regulatory community that aspartame is safe,” Kevin Keane, interim president and chief executive officer of the American Beverage Association, said in a statement. “It’s a conclusion reached time and time again by food safety agencies around the world.”

Among scientists, many urged consumers to consider that despite the new classification from the IARC study, the JEFCA study didn’t change what it considers an acceptable daily amount of aspartame. The agency has previously determined that an adult weighing 70 kilograms, or 154 pounds, can consume 9 to 14 cans of soda daily, each containing 200 to 300 milligrams of aspartame, and stay within a safe range of consumption.

‘Evidence Is Weak’

“If there was any cause for concern, they would have adjusted the current acceptable daily intake,” said Arnold Baskies, the past chairman of the national board of directors of the American Cancer Society. “The US Food and Drug Administration has affirmed and reaffirmed aspartame’s safety.” Added Paul Pharoah, a professor of cancer epidemiology at Cedars-Sinai Medical Center in Los Angeles: “The evidence that aspartame causes primary liver cancer, or any other cancer in humans, is weak. The general public should not be worried.”

PepsiCo Inc.’s chief financial officer, Hugh Johnston, who has been with the food and beverage company since 1987, said that “hundreds of studies” over the years have found aspartame to be safe. “Aspartame is one of the few things that’s probably been around PepsiCo longer than I have,” Johnston said.

QuickTake: How to Understand Confusing Advice About Aspartame

The two WHO reports on aspartame and cancer come two months after another WHO report determined that artificial sweeteners might not help people lose weight. That review found that products containing aspartame and stevia — which are often marketed as diet foods — likely don’t help reduce body fat in the long term.

In a study released last year, researchers from France’s National Institute of Health and Medical Research, or Inserm, found that of 103,000 people studied, those who consumed high amounts of aspartame had a 15% higher risk of developing cancer.

High consumers who are getting aspartame from several beverage and food products each day “may be close” to reaching the daily recommended intake, the WHO’s Branca warned. “It’s the only very obvious recommendation to give: Bring down consumption. The benefit is not there, we know that.”

Potential Reaction

Any negative consumer reaction to the latest designation on aspartame would likely have an impact on several consumer-product companies. Throughout the carbonated-beverage business, from Diet Coke and Coke Zero Sugar, to Diet Pepsi and Diet Dr Pepper, aspartame is used to provide calorie-free sweetness. Of the top 10 carbonated soft drinks sold in the US, some 15% of them currently use aspartame, according to the trade publication Beverage Digest. Aspartame is used in a range of low-calorie foods and beverages, many consumed by pregnant women and young children.

“A lot of people around the world enjoy the taste of drinks made with aspartame or some aspartame blend, and I don’t see that changing,” said John Sicher, a beverage industry consultant and former publisher of Beverage Digest.

Still, as science evolves and consumers grow increasingly hungry for healthy, low-calorie foods and beverages, the industry is searching for natural alternatives to chemical-based sweeteners. Coca-Cola Co. in April did limited market testing on a Diet Coke that replaces aspartame with plant-based sweeteners, such as monk fruit and stevia.

“We think generally the soft drink companies are going to fight this” designation from the WHO, said Garrett Nelson, an industry analyst at CFRA.

--With assistance from Deena Shanker, Robert Langreth and Dasha Afanasieva.