If Aspartame Is a 'Possible Carcinogen,' Can You Still Drink Diet Coke?

Fact checked by Nick Blackmer

Key Takeaways

• Aspartame is a low-calorie artificial sweetener found in Diet Coke, sugar-free gum, and many other products.

• The World Health Organization has classified aspartame as a “possible carcinogen” based on limited evidence.

• More research is needed to prove a strong link between aspartame and cancer risk in humans.

The World Health Organization (WHO) today classified aspartame, a popular artificial sweetener, as a possible carcinogen. The decision was based on limited evidence, and doesn’t change the recommended acceptable daily intake levels for aspartame.

Aspartame is an artificial sweetener used in many low-calorie products like Diet Coke and sugar-free Jell-O. It was approved by the Food and Drug Administration (FDA) decades ago, but some people continue to question the safety of this sugar substitute.

The WHO’s cancer research group, the International Agency for Research on Cancer (IARC), uses four categories to classify carcinogens, or cancer-causing agents.

Aspartame is now listed in Group 2B alongside things like gasoline, lead, and whole-leaf aloe vera extract. Group 1 consists of harmful substances with “sufficient evidence of carcinogenicity in humans,” including tobacco smoke and ultraviolet radiation.

To be placed in Group 2B, the research group must find “limited evidence of carcinogenicity in humans,” or “sufficient evidence of carcinogenicity in experimental animals,” or “strong evidence that the agent exhibits key characteristics of carcinogens (regardless of whether from exposed humans or human cells or from experimental systems).”

“For current consumers of diet drinks, this news isn’t cause for major alarm. Aspartame has been classed in IARC’s Category 2B, which means there’s limited evidence that it might cause cancer, not that it does or is likely to,” Alexandra Jones, PhD, Senior Research Fellow in Food Policy and Law at the George Institute for Global Health in Australia, said in a statement.

Related: Sucralose vs. Aspartame: What’s The Difference?

How Dangerous Is Aspartame?

Some people have turned to aspartame and other artificial sweeteners as a way to reduce their sugar intake. Consuming too many added sugars has been linked to an increased risk of obesity, type 2 diabetes, and heart disease.

But with the news that aspartame is a “possible carcinogen,” some people may wonder if the swap from sugar to aspartame is worth it.

“No one ingredient or food increases cancer risk. It’s the amounts and patterns of food we consume over time, along with other genetic and lifestyle factors, that influence health risk,” Debbie Petitpain, MS, RDN, LDN, a registered dietitian in Charleston, South Carolina, and spokesperson for the Academy of Nutrition and Dietetics, told Verywell in an email.

Aspartame is one of six sweeteners currently approved by the FDA as “safe for the general population under certain conditions of use.” The FDA determined that it’s safe for most people to consume up to 50 mg/kg body weight of aspartame every day.

In tandem with IARC’s possibly carcinogenic classification, the Joint Expert Committee on Food Additives (JECFA) reaffirmed the acceptable daily intake of aspartame is 40 milligrams/kilogram of body weight.

“To exceed this, a 150-pound person, who would have a daily limit of 3,400 milligrams, would have to consume 19 cans of diet soda or more than 85 individual packets of aspartame every day over the course of their lifetime,” Petitpain said.

The available research on aspartame and cancer has offered some mixed results. A controversial animal study from 2006 linked aspartame to cancer in rats, but an observational study published the same year didn’t find a link between aspartame and an increased risk of brain cancers in humans.

However, an observational study in 2022 suggested that aspartame may increase overall cancer risk in humans, especially obesity-related cancers and breast cancer.

The FDA maintains that aspartame is safe for most people and the website states that the agency 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.”

“When a substance or product may have cancer-causing potential, it is essential to weigh the benefits and health risks. The most important piece is for individuals to have transparency on the safety information to make an informed decision,” Sudarsan Kollimuttathuillam, MD, a medical oncologist and hematologist at City of Hope in California, told Verywell in an email.

Related: Is Splenda Really As Bad for You As Recent Research Suggests?

Try Another Sweetener If You Are Worried About Aspartame

If you’re concerned about aspartame, look at nutrition labels to determine if your favorite products contain this artificial sweetener. It is also known by the brand names NutraSweet and Equal.

You don’t have to give up all sweets if you decide to avoid aspartame. Petitpain recommends using some of the other FDA-approved non-nutritive sweeteners like saccharin or sucralose or one of the sweeteners, such as stevia, monk fruit, or allulose, that the FDA has said are “Generally Recognized as Safe.”

She also said that some people can decide to consume foods and drinks with low amounts of added sugar.

“Examples include beverages such as water, unsweetened tea or coffee, 100% juices or milk and snacks including fruits, nuts, unsweetened yogurt and other whole foods,” she said.

For now, the only strong health advisory against aspartame is for people with phenylketonuria (PKU) who can’t break down the protein phenylalanine which is found in aspartame.

“If you have concerns about aspartame or its potential impact on your health, it is always advisable to consult with a healthcare professional who can provide personalized advice based on your specific circumstances,” Kollimuttathuillam said.

What This Means For You

Researchers are still studying the possible link between aspartame and cancer in humans. For now, they say it’s still safe to consume products like Diet Coke in moderate amounts.