Aspartame and Cancer Risk

Aspartame has been reviewed by many international health organizations to see whether it increases cancer risk. At this time, there is no consistent link between aspartame and cancer, although more research needs to be done.

What is aspartame? 

Aspartame is an artificial sweetener that has been used in the United States since the early 1980s. It is used in many foods and drinks. Because it is much sweeter than sugar, less of it can be used to get the same level of sweetness.

Aspartame is commonly used as a:

• Tabletop sweetener
• Sweetener in prepared foods and drinks
• Sweetener in recipes that don’t require too much heating, because heat breaks it down
• Flavoring in some medicines, chewing gums, and toothpastes

Does aspartame cause cancer?

Concerns about whether aspartame causes health problems, including cancer, have been around for many years.

What expert agencies say

In general, the American Cancer Society (ACS) does not determine whether something should be considered a carcinogen (something that can cause cancer). Instead, ACS looks to other respected organizations for help with this.  

Several agencies and food regulatory authorities have made the following determinations based on current research.

The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), has classified aspartame as “possibly carcinogenic to humans” (Group 2B), based on limited evidence that it might cause cancer in people, specifically liver cancer. IARC also notes there is limited evidence for cancer in lab animals and limited evidence related to possible mechanisms for it causing cancer.

The Joint FAO/WHO Expert Committee on Food Additives (JECFA) completed a dietary exposure assessment and concluded that “evidence of an association between aspartame consumption and cancer in humans is not convincing” and that dietary exposure to aspartame does not pose a health concern.

The director of the Department of Nutrition and Food Safety for WHO has concluded 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.”

The US Food and Drug Administration (FDA) is responsible for the safety of ingredients added to foods in the US, including aspartame. The FDA has stated: “Scientific evidence has continued to support the FDA’s conclusion that aspartame is safe for the general population when made under good manufacturing practices and used under the approved conditions of use.”

The European Food Safety Authority (EFSA) regulates food additives in the European Union. After completing a risk assessment on aspartame in 2013, the EFSA stated that “aspartame and its breakdown products are safe for human consumption at current levels of exposure.”

To learn more about how cancer causes are studied and classified, see How Do We Know What Causes Cancer? and Known and Probable Human Carcinogens. 

What do studies show?

Researchers use 2 main types of studies to try to determine if something might cause cancer:  

• Lab studies are done using lab animals or cells in lab dishes.  
• Studies in people compare groups to see if people with higher exposures are more likely to develop cancer.  

Often, neither type of study provides conclusive evidence on its own. Both human and lab-based studies are reviewed when trying to figure out whether something causes cancer.  

Lab studies

Studies in lab rats published by a group of Italian researchers in the late 2000s suggested aspartame might increase the risk of some blood-related cancers (leukemias and lymphomas) and other types of cancer. However, these studies had some flaws that made their results hard to interpret.

Studies in people

Studies in people on the possible links between aspartame and cancer (including blood-related cancers) have not had consistent findings. Some studies have suggested a possible link, but others have not.

A recent review of 90 studies of non-sugar sweeteners, including aspartame, did not find a consistent link to a risk of any cancer type.

How much aspartame can a person safely consume ?

In the US, artificial sweeteners, such as aspartame, are regulated by the FDA. These products must be tested for safety and approved by the FDA before they can be used.

The FDA also sets an acceptable daily intake (ADI) for each sweetener, which is the maximum amount considered safe to consume each day during a person’s lifetime.

• The FDA has set the ADI for aspartame at 50 milligrams per kilogram (1 kg = 2.2 lb) of body weight per day (50 mg/kg/day). 
• Both JECFA and the EFSA recommend a slightly lower ADI for aspartame, at 40 mg/kg/day.

To help put these levels in perspective, the FDA estimates that a person weighing 60 kg (132 lb) would have to consume about 75 packets of aspartame in a day to reach the upper end of the ADI of 50 mg/kg/day. 

A person weighing 70 kg (154 lb) would have to consume at least 9 to 14 cans of diet soda per day (depending on the level of aspartame in each can) to exceed the ADI of 40 mg/kg/day used by JECFA/EFSA.

Who should avoid aspartame?

Aspartame hasn’t been linked conclusively to any specific health problems except for people with phenylketonuria (PKU). PKU is a rare genetic disorder (present at birth) in which the body can't break down phenylalanine, an amino acid found in many foods and aspartame. This is why any products containing aspartame must carry the warning “PHENYLKETONURICS: CONTAINS PHENYLALANINE.”

For other people who want to avoid aspartame, look for this warning or check the ingredient labels before buying or eating foods or drinks. If aspartame is in the product, it will be listed.

Information from other organizations

The following organizations may also offer helpful information. The American Cancer Society is not affiliated with or responsible for these resources.

International Agency for Research on Cancer (IARC)

• Aspartame hazard and risk assessment results released

European Food Safety Authority (EFSA)

• Aspartame
• EFSA Explains the Safety of Aspartame

US Food and Drug Administration (FDA)

• Aspartame and Other Sweeteners in Food

National Cancer Institute (NCI)

• Artificial Sweeteners and Cancer