Is aspartame bad for you? Health concerns explained
Approved worldwide, but labeled a 'possible' carcinogen by WHO's IARC in 2023.
Also listed as: E951, INS 951, NutraSweet, Equal, Canderel
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What is Aspartame?
Aspartame is a low-calorie sweetener about 200 times sweeter than sugar. It is made from two amino acids, aspartic acid and phenylalanine, and is used in diet sodas, sugar-free gum and 'light' yogurts.
Why manufacturers use it
It gives sweetness with almost no calories, so manufacturers use it to make sugar-free and diet versions of foods and drinks.
Where you'll find it
- Diet sodas
- Sugar-free gum
- Light yogurts
- Tabletop sweeteners
- Some chewable vitamins
Potential health concerns
- IARC classified it as 'possibly carcinogenic' (Group 2B) in 2023 based on limited evidence for liver cancer.
- People with phenylketonuria (PKU) must avoid it because they can't break down phenylalanine.
- Some people report headaches, though controlled studies are inconsistent.
How it works in the body
In the gut, aspartame breaks down into phenylalanine, aspartic acid and a small amount of methanol — the same compounds found in larger amounts in foods like milk, meat and fruit juice.
How much is too much
JECFA and EFSA: 40 mg per kg of body weight per day; FDA: 50 mg/kg. A 70 kg adult would need roughly 9–14 cans of diet soda daily to reach the JECFA limit.
What scientific studies indicate
Large reviews by EFSA (2013) and JECFA (2023) found no convincing evidence of harm at normal intakes. Some observational studies link heavy artificial sweetener use to cancer or heart disease, but they can't prove cause and effect.
Regulatory status by country
United States
Permitted; labels must warn about phenylalanine.
European Union
Permitted as E951 with a phenylalanine warning.
Canada
Permitted with a phenylalanine statement.
Australia / NZ
Permitted (code 951).
Why it's rated this color
- Permitted in the US, EU, Canada and Australia/NZ.
- WHO's JECFA reviewed the same data in 2023 and kept the existing safe daily limit.
- The 2B label signals uncertainty, not proven harm, so the evidence is mixed.
Sources and original research
- Aspartame hazard and risk assessment results released — World Health Organization, 2023
- Scientific Opinion on the re-evaluation of aspartame (E 951) — EFSA Journal, 2013
- Aspartame and Other Sweeteners in Food — U.S. Food and Drug Administration
Last reviewed November 2026. Educational information, not medical advice.
Is Aspartame in your food?
Scan your label and get a verdict for every ingredient in seconds.