Aspartame
IARC class 2B (possibly carcinogenic, 2023); intake limits apply.
- Category
- Sweeteners
- Acceptable daily intake
- 40 mg/kg body weight/day (EFSA)
- Vegan
- Yes
- Vegetarian
- Yes
What it is
Aspartame (E951) is an artificial, non-saccharide sweetener used as a sugar substitute in many foods and beverages. It is approximately 200 times sweeter than sucrose (table sugar).
How it is used in food
200× sweeter than sugar.
Commonly found in- Diet sodas (e.g., Diet Coke)
- Sugar-free chewing gum
- Low-calorie yoghurts and desserts
- Tabletop sweeteners (e.g., Equal, NutraSweet)
Health and safety
In 2023 IARC classed it "possibly carcinogenic". People with the genetic condition PKU must avoid it entirely.
Aspartame is one of the most rigorously tested food ingredients in the world. While heavily debated in the public sphere and recently classified by the IARC (WHO) as "possibly carcinogenic to humans" (Group 2B), regulatory bodies like EFSA and the FDA continue to affirm its safety at current consumption levels.
Phenylketonuria (PKU)
Aspartame breaks down into phenylalanine during digestion. People with the rare genetic disorder phenylketonuria (PKU) cannot metabolize phenylalanine, leading to toxic build-up and brain damage. Products containing E951 must carry a mandatory warning label for this group.
Carcinogenicity debate
In 2023, the IARC classified aspartame as "possibly carcinogenic" (Group 2B, same category as aloe vera extract and pickled vegetables) based on "limited evidence" for liver cancer. However, the JECFA (WHO) risk assessment committee concluded that the evidence was not convincing enough to alter the acceptable daily intake of 40 mg/kg.
WHO kept its intake limit — about 12 cans of diet soda a day for an adult.
Regulatory status
| Region | Status | Notes |
|---|---|---|
| Australia & New Zealand FSANZ |
Permitted, must be declared on the label | Permitted. “Contains phenylalanine” |
| European Union EFSA / European Commission |
Permitted, must be declared on the label | Authorised under Regulation (EC) No 1333/2008. Foods containing it must declare the phenylalanine source for people with phenylketonuria. “Contains a source of phenylalanine” |
| United States FDA (Food and Drug Administration) |
Permitted, must be declared on the label | Approved by the FDA with an ADI of 50 mg/kg bw/day. “Phenylketonurics: Contains Phenylalanine” |
Identification on labels
- E-number
- E951
Also printed asEqual · NutraSweet
Alternatives to this additive
- E960: Steviol glycosides — Provides zero-calorie sweetness without synthetic chemistry.
- E955: Sucralose — Does not contain phenylalanine.
How it is made
It is a methyl ester of a dipeptide constructed from two natural amino acids: aspartic acid and phenylalanine. It is synthesized industrially using chemical or enzymatic processes.
- Amino Acid Preparation — L-aspartic acid and L-phenylalanine are produced via microbial fermentation.
- Esterification — L-phenylalanine is reacted with methanol to form phenylalanine methyl ester.
- Coupling — The two amino acids are chemically or enzymatically bonded together to form the aspartame molecule.
- Purification — The product is crystallized, washed, and dried into a fine white powder.
Worth knowing
Composed of two amino acids joined together.
Conclusion
E951 is deemed safe by global regulatory authorities within the Acceptable Daily Intake. However, it must be completely avoided by individuals with phenylketonuria (PKU). Consumers concerned about artificial sweeteners often opt for natural alternatives like Stevia.
References
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Open the appEntry last reviewed 2026-07-28.
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