Aspartame and mood, thinking in a small diet trial
What it found
In 28 healthy young adults, 8 days on a higher-aspartame diet led to more irritability and depression and worse spatial orientation than 8 days on a lower-aspartame diet.
Working memory and headaches did not differ.
What they found
Studies in people
Spatial orientation
Participants scored significantly better on spatial orientation tests after the low-aspartame diet than after the high-aspartame diet. Two participants had clinically significant cognitive impairment after the high-aspartame diet.
Working memory
Working memory scores did not differ significantly between the two diet periods. Two different participants had clinically significant impaired working memory after the high-aspartame diet.
Depression
Participants were significantly more depressed after the high-aspartame diet than after the low-aspartame diet. After the high-aspartame diet, 3 of 28 participants scored over 49, indicating mild to moderate clinical depression, while all 28 were in the normal range after the low-aspartame diet.
Irritability
Participants scored significantly higher on an irritability scale after the high-aspartame diet than after the low-aspartame diet.
Headaches
Only one participant reported a headache, so no difference in headache occurrence between the two diet periods could be established.
What the authors conclude
“Aspartame intake affected certain aspects of neurobehavioral performance.”
Also in their conclusions
- They say aspartame intake affected certain aspects of neurobehavioral performance, with weaker spatial orientation and more frequent irritability and depression after high-aspartame consumption than low aspartame consumption.
- They report that seven participants experienced clinically significant neurobehavioral conditions following the higher level of aspartame consumption.
- They state that "additional research is warranted to assess the safety of aspartame consumption and its implications for health."
How it was done
Aspartame is widely used but remains controversial, with mixed evidence on its effects on thinking, mood and headaches. The authors wanted to test it using diets controlled for body weight and energy needs, which earlier studies had not done.
They gave 28 healthy university students, aged 20 to 40, a high-aspartame diet (25 mg/kg body weight per day) for 8 days and a low-aspartame diet (10 mg/kg body weight per day) for 8 days, in random order, with a 2-week washout between. Participants ate only study foods and were their own controls. Cognition, mood, depression and headaches were measured after each diet period.
What it can’t tell you
- The sample was small and similar (healthy young university students), so the results may not apply to other groups.
- The study lasted only 8 days on each diet, so it cannot show what longer-term intake might do.
- The authors note the study had low statistical power, which makes it harder to detect real differences.
Who paid
- Funding
- Funded by NCRR NIH HHS (from the PubMed record).
The paper
- Title
- Neurobehavioral effects of aspartame consumption
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Lindseth GN, Coolahan SE, Petros TV, Lindseth PD (2014). Neurobehavioral effects of aspartame consumption. Research in nursing & health. doi:10.1002/nur.21595Free full textPubMed 24700203DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error