Is aspartame safe? Unraveling the science behind the controversy


by Baylor Scott & White Health

Aug 4, 2023

You may have heard the news that the World Health Organization (WHO) has reclassified aspartame, a popular artificial sweetener used in diet sodas, as a possible cancer-causing carcinogen. But the US Food and Drug Administration (FDA) disagrees, saying aspartame is safe for consumption.

Confused? You’re not alone. What does “possible carcinogen” mean, and should you be concerned? Here are the facts you need to know.

What is aspartame?

Aspartame is an artificial sweetener that was approved by the FDA in 1974. It rose in popularity as an alternative sweetener for diet sodas and is now in over 95% of diet sodas on the market. The sweetener tastes about 200 times sweeter than sugar. Although it contains about the same number of calories as sugar, its intense sweetness means consumers use less aspartame than they would sugar.

What does it mean to be a “carcinogen?”

The WHO’s International Agency for Research on Cancer uses a scaled ranking system to classify compounds based on how cancer-inducing they may be. A compound ranked 1 has no link to cancer, whereas a compound ranked 3 has a clear link to cancer.

The organization recently changed aspartame’s status to 2B, which is defined as being “possibly carcinogenic to humans.” Other compounds with this 2B status include gasoline and engine exhaust.

However, the FDA came out with a statement disputing the WHO’s new classification of aspartame.

“The FDA disagrees with IARC’s conclusion that these studies support classifying aspartame as a possible carcinogen to humans,” the FDA wrote in a statement. “FDA scientists reviewed the scientific information included in IARC’s review in 2021 when it was first made available and identified significant shortcomings in the studies on which IARC relied.”

The FDA statement says aspartame is one of the most studied food additives and is safe for normal consumption.

So, is aspartame safe?

How much is too much? Although the WHO and FDA disagree on the new determination, most diet soda drinkers can stay calm.

“You definitely don’t have to throw out all of your diet sodas,” said Carol Nwelue, MD, medical director of internal medicine at Baylor Scott & White All Saints Medical Center – Fort Worth. “However, the FDA recommends drinking no more than 12 cans of a diet soda containing aspartame per day.”

Officials from the WHO said the concern is for high consumers of aspartame, and that occasional diet soda drinkers should not be concerned.

Dr. Nwelue and the WHO officials noted that more research is needed. In the meantime, if you are a heavy consumer of diet sodas, consider opting for another beverage. Healthy alternatives include:

  • Water flavored with fresh fruit
  • Coconut water
  • Sparkling water
  • Herbal tea

“This is definitely something for us to watch,” Dr. Nwelue said. “If you can, consider decreasing your intake.”

If you have questions about nutrition and your cancer risk, talk to your doctor or find a doctor near you.

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