Does aspartame have health risks? Here's what studies have found about the sweetener as WHO raises safety questions.

Aspartame, an artificial sweetener 200 times as potent as regular granulated sugar, is used in thousands of products on grocery store shelves, from sodas and drink mixes to low-cal condiments and desserts. Yet some consumers and researchers have questioned what it means for people's health.

On Thursday, July 13, the World Health Organization's International Agency for Research on Cancer released a report categorizing the artificial sweetener as "possibly carcinogenic to humans."

"The assessments of aspartame have indicated that, while safety is not a major concern at the doses which are commonly used, potential effects have been described that need to be investigated by more and better studies," Dr, Francesco Branca, director of the WHO's Department of Nutrition and Food Safety, said in a statement.

Robert Rankin, president of the Calorie Control Council, an international association representing the low- and reduced-calorie food and beverage industry, said in a statement to CBS News that a review by the U.N.'s Joint FAO/WHO Expert Committee on Food Additives reaffirms the overwhelming body of evidence that aspartame is safe.

"To assert otherwise is misleading, inaccurate, and fear mongering to the nearly 540 million people globally living with diabetes and millions of others managing their body weight who rely on and/or chose products that contain low- and no-calorie sweeteners such as aspartame," Rankin said.

"Carcinogenic" definition

The National Institute of Health's National Cancer Institute defines a carcinogen as "any substance that causes cancer."

Carcinogens can occur naturally in the environment or may be generated by humans, the NIH adds, and typically work by interacting with a cell's DNA to produce mutations.

"To date, over 500 substances have been identified as definitive, probable, or possible carcinogens for humans. This includes items like asbestos, automobile exhaust, processed meat or ultraviolet rays," the NIH's National Human Genome Research Institute's website notes. "Exposure to a carcinogen does not necessarily mean you will get cancer. A number of factors influence whether a person exposed to a carcinogen will ultimately develop cancer."

Is aspartame bad for you?

Aspartame entered the market as a low-calorie sweetener in 1981 and has since become a key ingredient in foods and beverages across North America and beyond. It has been approved by the U.S. Food and Drug Administration for use in food products, with the agency concluding the additive is "safe for the general population." 

"Aspartame is one of the most studied food additives in the human food supply," the FDA says. "To determine the safety of aspartame, the FDA has reviewed more than 100 studies designed to identify possible toxic effects, including studies that assess effects on the reproductive and nervous systems, carcinogenicity, and metabolism." 

The U.N.'s Joint FAO/WHO Expert Committee on Food Additives says the latest data reaffirms that it is safe to consume aspartame up to the previously established acceptable daily intake (ADI) amount — 40 milligrams per kilogram of body weight, per day.

But questions about aspartame's safety have surfaced over the years.

In May, WHO said the sweetener is not proven to help with weight loss, and that long-term use may have "potential undesirable effects," such as an "increased risk of type 2 diabetes, cardiovascular diseases, and mortality in adults."

A 2021 research paper, published in the peer-reviewed journal Nutrients, noted that "the results of its long-term use remain difficult to predict."

The authors cited other research suggesting a possible association between the consumption of aspartame and the development of type 2 diabetes, though they conclude that the connection "is unclear." The sweetener may also cause mood disorders, mental stress and depression, they noted. 

The authors reviewed some research on rodents that indicated aspartame "may have carcinogenic properties," but they said it was "not possible to conclusively determine that aspartame is carcinogenic for humans."

Other studies looking at the possible link between aspartame and cancer have not been consistent, according to the American Cancer Society.

• WHO warns against artificial sweeteners for weight loss in new guidance

Aspartame isn't the only sweetener to be reexamined recently.

A study published in February found erythritol, a zero-calorie sugar substitute used to sweeten low-cal, low-carb and "keto" products, is linked to higher risk of heart attack, stroke and death.

Sugar-free products containing erythritol are often recommended for people with obesity, diabetes or metabolic syndrome as ways to manage sugar and calorie intake. People with these conditions are already at higher risk for adverse cardiovascular events such as stroke.

In response to that study, Rankin, of the Calorie Control Council, told CBS News that the results were "contrary to decades of scientific research showing low- and no-calorie sweeteners like erythritol are safe, as evidenced by global regulatory permissions for their use in foods and beverages, and should not be extrapolated to the general population, as the participants in the intervention were already at increased risk for cardiovascular events."

Ahead of WHO's expected declaration on aspartame, Rankin said, "Consumers deserve facts, and the fact is aspartame is safe and one of the most widely studied food ingredients, which is why the Calorie Control Council is gravely concerned about any unsubstantiated and misleading assertions that contradict decades of science and global regulatory approvals."

Elizabeth Napolitano contributed to this report.

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• Aspartame
• Food and Drug Administration
• Cancer
• World Health Organization
• FDA