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Is Aspartame a Carcinogen?

Updated: Oct 11, 2023

I am sure you have seen the headlines by now. The World Health Organization (WHO) is set to declare Aspartame a possible carcinogen. A carcinogen is a substance that causes cancer. Should we start worrying about our aspartame intake? What foods have aspartame? Most importantly, how can we understand this news in the context of the research?

cup of soda

What is Aspartame?

Aspartame is an artificial sweetener sold under the brand names Equal, NutraSweet, and Canderel. It is 200 times sweeter than sucrose, so very small amounts are needed to produce a taste as sweet as regular sugar. It is commonly found in sodas, diet beverages, and sugar-free sweets such as Crystal Lite, zero-sugar Snapple, Diet Coke, Diet Pepsi, Trident gum, sugar-free Orbit gum, sugar-free Jell-O, and Maple Grove Farms sugar-free syrup. It is not commonly used in hard candies because it is not stable under the high heat necessary to make these confectionaries.

Recent Research on Aspartame Carcinogenicity

Study that Looked at Aspartame Intake and Risk of Cancer

There was an observational study done in France and published in March of 2022 that looked at intake of various artificial sweeteners and risk of cancer. The researchers collected 24 hour diet records from more than 100,000 participants and tallied up how much of various artificial sweeteners, including aspartame, participants consumed.

They then divided participants into three categories based on their intake. People who consumed none of the sweetener were in one group, and the rest of the participants were divided into two groups based on quantity of intake. Those who were in the lower half of intake quantity were in the second group, and those who were in the higher half of intake quantity were in the third group.

The average intake of aspartame in the low intake group was 3mg, and the average intake of aspartame in the high aspartame group was 47mg. To understand what these quantities are, here are some examples of foods and their aspartame content:

  • 1 can diet Coke or diet Pepsi: 200mg aspartame

  • 1 piece Trident gum:19mg aspartame

The results showed that high aspartame consumers were at slightly higher risk of certain cancers than the no aspartame group.

Discussion on the Research of Aspartame Intake and Cancer Risk

My biggest question about this study is how all the participants had such low aspartame intake, especially the supposed high aspartame consumers. Average aspartame intake in the United States is much higher than either group's aspartame intake. One study totaled average aspartame intake in the United States at 4.9mg/kg/day, which for a 150lb person is about 330mg, or about 1.5 cans of diet soda worth of aspartame.

Perhaps French people consume way less aspartame than Americans. Perhaps there are issues with the study design. Usually diet records, the method used in this study to collect data, are more accurate than other diet record methods. In this study, the diet records were validated against interviews conducted by a dietitian and blood and urine biochemical markers of intake. This should help improve accuracy.

The study authors posit that the lower aspartame intake might be due to the study participants' ages being higher, and older people tend to consume less aspartame.

If all the information is correct, it would seem that this study may actually underestimate the risk of cancer from aspartame. Still, aspartame is poised to only be in the "possibly carcinogenic" group. Let's take a look at the categories WHO uses to stratify carcinogenicity.

How Does WHO Decide if Aspartame is a Carcinogen?

WHO has a cancer research division called the International Agency for Research on Cancer. They look at the research on different substances, and based on the strength of research, they determine the substance's likelihood of being a carcinogen. There are four categories that correspond to four levels of quality of evidence. You can look here for more details of this classification system. In short, these are the four categories:

Carcinogenic to Humans: The first category requires the highest level of evidence.

Probably Carcinogenic to Humans: The next category has slightly weaker evidence for carcinogenicity.

Possibly Carcinogenic to Humans: This category has even weaker evidence to support carcinogenicity

Not Classifiable as to its Carcinogenicity to Humans: This category has not enough evidence to support that these items are carcinogenic.

What Else Falls into These Categories of Carcinogenicity?

Carcinogenic to Humans

  • alcoholic beverages

  • diesel engine exhaust

  • being a firefighter or painter

  • processed meats

Probably Carcinogenic to Humans

  • being a hairdresser or barber

  • working night shift

  • red meat

  • beverages above 149° F

Possibly Carcinogenic to Humans

  • aloe vera extract, ginkgo biloba extract, kava extract

  • gasoline engine exhaust and gasoline

  • working in dry cleaning or textile manufacturing

  • traditional Asian pickled vegetables

  • melamine

Not Classifiable as to its Carcinogenicity in Humans

  • chlorinated drinking water

  • working in glass manufacturing or leather goods manufacturing

  • hair coloring products

  • tea

  • caffeine

Is Aspartame a Carcinogen?

The bottom line is that there is some evidence that links aspartame to increased risk of certain cancers. It falls under the third out of four levels of evidence--the weakest level of evidence linking an item to cancer risk.

Anyone who understood the research until now is not going to make any different recommendations regarding aspartame intake with this WHO classification of aspartame as possibly a carcinogen. It was never shown to be a health-promoting item. Still, for some people, there are other food ingredients that may be worse for their health than aspartame, and aspartame may be a reasonable substitute in small quantities.

An interesting but not surprising discovery I made while reading the research on aspartame was that there are a few industry websites that promote aspartame's safety. I'll link them here for your reading enjoyment. is a website supported by American Beverage, a trade association for the beverage industry. is a website supported by Calorie Control Council, is a trade association for the low-calorie and reduced-calorie beverage industry.

Should We Fear Aspartame?

I think it is really important to understand this information in its context. This new WHO classification is a great news headline. It promotes fear, clicks, and income for news organizations. Why are items that have higher levels of evidence for their carcinogenicity not getting the same press? Alcoholic beverages, processed meat, and red meat all have stronger evidence of their carcinogenicity. Somehow society has come to be more suspicious of some industries than others, and fearmongering in these industries is easier.

I am not suggesting to spread fear about alcohol, processed meats, or red meat. I think fear is not necessary to understand the evidence and make an educated decision about food intake. I think we can just state and understand that some items have some level of evidence of carcinogenicity, and with that, individuals can make a calm and educated decision about whether to eat these items and how much they think is reasonable for their health.

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