Aspartame is a non-carbohydrate, non-nutritive artificial sweetener that is about 200 times sweeter than (sucrose) regular or table sugar, with almost zero calorie value. It contains two amino acids, phenylalanine and L-aspartic acid, bonded with a methyl ester. Because only a tiny amount provides the desired sweetness with almost no calories, aspartame has become a popular sugar substitute in diet (sugar-free) products, dairy items such as yogurt and breakfast cereals, diet beverages, hot drinks like coffee and tea, canned foods, jams, jellies, chewing gum, toothpaste, and even pharmaceutical products such as cough drops and chewable vitamins.
Recently, aspartame attracted worldwide attention after the International Agency for Research on Cancer (IARC) the specialized cancer agency of the World Health Organization (WHO) evaluated its cancer risk in July 2023.
Let’s explore what this means for everyday consumers.
WHAT DID WHO/IARC FIND?
The IARC classified aspartame as “possibly carcinogenic to humans” (Group 2B).
In simple terms, this means that a cancer risk cannot be ruled out, but the human evidence is still weak and inconclusive.
The classification is based on limited evidence for liver cancer (hepatocellular carcinoma) in humans, limited evidence in animal experiments, and limited mechanistic evidence.
Meanwhile, the WHO/FAO Joint Expert Committee on Food Additives (JECFA) reviewed the same data and reaffirmed that aspartame remains safe at the current Acceptable Daily Intake (ADI) of 0–40 mg per kg of body weight per day.
This shows that the hazard has been identified, but the actual risk from typical intake remains very low.
WHAT IS CANCER?
Before going further, let’s quickly understand what cancer is.
Cancer is a group of diseases marked by the uncontrolled growth and spread of abnormal cells. These cells can invade nearby tissues and, in some cases, spread to other parts of the body a process called metastasis.
Infections, radiation, genetic changes, and certain chemicals can all trigger these harmful mutations.
HOW IARC CLASSIFIES CARCINOGENS
Now let’s see how IARC decides whether something is cancer-causing.
The agency groups substances according to the strength of evidence:
• Group 1: Carcinogenic to humans – Clear evidence of cancer risk (e.g., tobacco smoke, asbestos).
• Group 2A: Probably carcinogenic to humans – Limited human evidence but stronger animal evidence (e.g., shift work involving night duty, red meat in high amounts).
• Group 2B: Possibly carcinogenic to humans – Limited human evidence and weaker animal data (e.g., aspartame, very hot drinks above 65 °C).
• Group 3: Not classifiable – Evidence is inadequate.
• Group 4: Probably not carcinogenic – Evidence suggests no risk.
Aspartame now sits in Group 2B, alongside everyday exposures such as very hot beverages.
This means scientists cannot dismiss a cancer link, but the proof is not strong enough to call it “probable.”
HOW ASPARTAME IS METABOLIZED
Next, let’s explore what happens inside the body.
Aspartame is broken down in the gastrointestinal tract into methanol, phenylalanine, and aspartic acid. The methanol is further oxidized in the liver to formaldehyde and then to formic acid.
These metabolites especially formaldehyde are of interest because formaldehyde is classified as carcinogenic to humans (Group 1).
However, scientific assessments, including those reviewed by the European Food Safety Authority (EFSA), show that the amount of formaldehyde produced from normal aspartame intake is extremely small compared with the formaldehyde naturally produced by human metabolism.
At the ADI of 40 mg/kg body weight per day, formaldehyde from aspartame contributes only about 0.3–0.4 % of the body’s natural daily formaldehyde turnover.
In simple words, typical consumption is unlikely to raise formaldehyde levels enough to cause harm.
WHY FORMALDEHYDE RAISES CONCERNS
Even so, formaldehyde itself is a known carcinogen.
For example, if someone consumed around 600 mg of aspartame (roughly 1 liter of certain sugar-free sodas), about 60 mg of formaldehyde could theoretically be generated during metabolism.
While this may sound alarming, remember that the ADI for aspartame is far higher 40 mg/kg body weight per day.
A 70 kg adult would need to drink roughly 9 to 14 cans of diet soda every day, without other aspartame sources, to approach or exceed the ADI.
So, staying within normal limits keeps exposure well below dangerous levels.
HUMAN STUDIES AND RISK ASSESSMENT
Let’s now look at human data. Observational studies give a mixed picture.
• The large French NutriNet-Santé cohort reported a small increase in overall cancer risk among high consumers of artificial sweeteners, including aspartame.
• Some other cohort studies, however, have found no convincing association between aspartame intake and cancer.
Because these studies depend on people reporting what they eat and can be affected by other factors like weight, diabetes, or daily habits they cannot clearly prove that aspartame itself causes cancer.
After reviewing these data, both IARC and JECFA concluded that there is limited evidence of a link and that current consumption patterns remain within a margin of safety.
DOES ASPARTAME DEFINITELY CAUSE CANCER?
Here’s the key takeaway: No.
• The IARC classification of “possibly carcinogenic” simply signals a potential hazard and the need for continued research.
• It does not mean that aspartame will cause cancer in everyone who consumes it.
• Dose and duration matter. Excessive intake over many years may increase theoretical risk, but normal consumption within the ADI is considered safe by WHO, FAO, EFSA, and other major health authorities.
CONCLUSION
To sum it up, aspartame remains one of the most thoroughly studied food additives.
Based on current evidence, moderate consumption within the ADI of 0–40 mg per kg of body weight per day is considered safe for the general population.
Future studies will clarify remaining uncertainties, but for now, aspartame sits in the same risk category as very hot drinks worthy of observation, not panic.
FAQs about Aspartame and Cancer
1. What is aspartame?
Aspartame is a low-calorie artificial Because these studies depend on people reporting what they eat and can be affected by other factors like weight, diabetes, or daily habits they cannot clearly prove that aspartame itself causes cancer.
sweetener about 200 times sweeter than table sugar. It is used in diet sodas, sugar-free gums, yogurts, and many other foods and drinks.
2. Is aspartame banned anywhere?
No. Aspartame is approved for use in more than 90 countries, including the United States, the European Union, and Pakistan, provided daily intake stays within the acceptable limit.
3. What does “possibly carcinogenic to humans” mean?
This IARC Group 2B classification signals that there is limited evidence of cancer risk in humans and animals. It does not prove that aspartame causes cancer in normal dietary amounts.
4. What is the safe daily intake?
The WHO/FAO Joint Expert Committee on Food Additives (JECFA) recommends an Acceptable Daily Intake (ADI) of 0–40 mg per kg of body weight.
For a 70 kg adult, this equals about 9–14 cans of diet soda per day, which is far more than most people consume.
5. Does aspartame release formaldehyde in the body?
Yes, but the amount produced is extremely small compared with the formaldehyde naturally generated by human metabolism and remains well below harmful levels at normal intake.
6. Who should avoid aspartame?
People with phenylketonuria (PKU) a rare inherited disorder must avoid aspartame because they cannot metabolize phenylalanine, one of its components.
DISCLAIMER
This article is for educational purposes only and should not replace medical advice. Individuals with health conditions or dietary concerns should consult a qualified healthcare professional before making major changes to their diet.
CALL TO ACTION
Stay informed about the science behind everyday food ingredients.
Share this article to spread evidence-based knowledge, and always read nutrition labels to keep your intake of artificial sweeteners within recommended limits.
REFERENCES
1. WHO/IARC. Aspartame: IARC Monographs evaluation of the carcinogenicity of aspartame. July 2023.
2. WHO/JECFA. Aspartame hazard and risk assessment results released. July 2023.
3. EFSA Panel on Food Additives. Scientific Opinion on the re-evaluation of aspartame (E951). EFSA Journal. 2013;11(12):3496. 4. Chazelas E, et al. Artificial sweeteners and cancer risk in the NutriNet-Santé cohort. PLoS Med. 2022;19(3):e1003950.