Aspartame

Studies in people

• Open question

  Mood and cancer risk²

  Scientists do not yet know whether daily aspartame intake causes mood changes or raises cancer risk in people.

• Open question

  Overall health effects³

  A review found studies on aspartame’s effects on weight, diabetes, children, unborn babies, allergies, and cancer need more research.

• Concern

  Headaches and seizures⁴

  Some reports link long-term, high-dose aspartame to headaches, seizures, blindness, and changes in thinking or behavior.

• Concern

  Cancer risk in people with diabetes⁵

  In people with diabetes, eating a lot of aspartame was linked to stomach cancer, but the numbers were small.

• Concern

  Mood and thinking⁶

  People eating more aspartame felt more irritable and depressed and did worse on some thinking tests.

• Concern

  Autism risk in boys⁷

  Boys whose mothers had aspartame daily in pregnancy were more often diagnosed with autism, but this study cannot prove cause.

• No harm found

  Breast cancer risk⁸

  In nearly 30 years of following women, aspartame intake was not linked to breast cancer.

• Open question

  Appetite and fullness⁹

  In six people, aspartame did not raise gut hormones tied to fullness, but phenylalanine may affect appetite.

Animal and lab studies only

• Concern

  Cancer in animals¹³

  In animal studies, aspartame was linked to more cases of several types of cancer.

• No harm found

  DNA damage in cells¹⁴

  In lab and animal studies, aspartame showed no signs of causing gene changes.

• Concern

  Cancer risk in rodents¹⁵

  In animal studies, aspartame was linked to cancer, though some experts question how those tests were run.

• Concern

  Heart and blood vessel risk¹⁶

  In animal studies, aspartame sped up hardening of the arteries in mice with high blood fat.

• Concern

  Stomach cancer risk¹⁷

  In lab studies, aspartame may affect proteins tied to stomach cancer, but scientists do not yet know if this happens in people.

• Concern

  Oxidative stress and cell damage¹⁸

  In animal studies, aspartame may upset the body's natural balance and damage cells, possibly causing inflammation.

• Concern

  Endometriosis growth¹⁹

  In lab and animal studies, aspartame exposure worsened endometriosis by affecting oxidative stress and mitochondria.

• Concern

  Stroke risk²⁰

  Aspartame may contribute to ischemic brain injury by interacting with multiple targets, but further validation is required.

• Concern

  Gut bacteria and brain tumours²¹

  In animal studies, aspartame changed gut bacteria and turned on genes tied to brain tumour growth, but tumours did not grow faster.

Study type not stated

• Open question

  Brain and mood effects¹⁰

  Scientists do not yet know whether aspartame causes brain or mood problems, because the data is not consistent.

• Concern

  Cancer risk in people¹¹

  Experts looked at the research and said aspartame is possibly cancer-causing in people.

• Concern

  Blood sugar in diabetes¹²

  Aspartame may raise weight gain and blood sugar problems in type 2 diabetes, but scientists do not yet know for sure.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.

Expert panels that weigh all the research. Shown for context: the signal at the top does not count them. IARC rates whether something can cause cancer at all, not how likely it is at the amounts in food.

• UN and WHO food additive experts (JECFA), 2023

  Acceptable daily intake: up to 40 mg per kg of body weight.

• WHO cancer agency (IARC), 2023

  Possibly causes cancer in people (Group 2B).