Don’t take sugar substitutes if you want your brain to function normally and it’s a big warning for diabetic patients, an alarming study by American Academy of Neurology suggests

Artificial sweeteners have long been marketed as a way to enjoy sweetness without the calories of sugar. Found in products ranging from diet sodas and flavored waters to low-calorie desserts and sugar-free yogurts, these sugar substitutes have become a common part of modern diets.

However, research suggests that consuming high amounts of certain low- and no-calorie sweeteners may be associated with faster declines in memory and thinking abilities over time.

A study published on September 3, 2025, in the medical journal of the American Academy of Neurology, found that people who consumed the highest amounts of seven commonly used artificial sweeteners experienced faster cognitive decline compared with those who consumed the lowest amounts.


Researchers estimated that the difference in cognitive decline was equivalent to approximately 1.6 years of additional brain aging.

However, scientists emphasized that the findings show an association, not proof that artificial sweeteners directly cause cognitive decline.

What did the artificial sweetener study find?

The study followed 12,772 adults in Brazil with an average age of 52 years. Participants were monitored for an average of eight years, during which researchers assessed changes in memory, language skills and overall thinking ability.

The research team examined seven low- and no-calorie sweeteners commonly found in processed foods:

• Aspartame
  
• Saccharin
  
• Acesulfame-K (Ace-K)
  
• Erythritol
  
• Xylitol
  
• Sorbitol
  
• Tagatose
  

Participants reported their dietary intake at the beginning of the study through food questionnaires that recorded what they had eaten and consumed over the previous year.

Researchers then divided participants into three groups based on their total daily sweetener consumption.

The lowest consumption group consumed an average of 20 milligrams per day, while the highest consumption group consumed approximately 191 milligrams per day.

For comparison, researchers noted that the highest level of aspartame consumption was roughly equivalent to one can of diet soda per day.

High sweetener consumption was linked to 62% faster cognitive decline

During the study period, participants underwent cognitive tests at the beginning, middle and end of the research.

The tests evaluated several brain functions, including:

• Verbal fluency
  
• Working memory
  
• Word recall
  
• Processing speed
  
• Overall cognitive performance
  

After adjusting for factors that can influence brain health, including age, sex, high blood pressure and cardiovascular disease, researchers found that people in the highest sweetener consumption group experienced cognitive decline 62% faster than those in the lowest consumption group.

The researchers estimated this difference was comparable to about 1.6 years of additional aging.

Participants in the middle consumption group also showed faster decline, with researchers estimating a decline rate 35% faster than the lowest consumption group, equivalent to approximately 1.3 years of aging.

The link was strongest among adults under 60

One of the most notable findings was that the association appeared stronger among younger participants.

When researchers analyzed results by age, they found that adults under the age of 60 who consumed higher amounts of sweeteners showed faster declines in:

• Overall cognitive performance
  
• Verbal fluency
  
• Memory-related abilities
  

However, researchers did not find the same association among participants older than 60.

The study also found that the relationship between sweetener consumption and cognitive decline appeared stronger among people with diabetes.

Researchers noted that people with diabetes are often more likely to use artificial sweeteners as alternatives to sugar because of concerns about blood glucose levels.

Which sweeteners were linked to cognitive decline?

Researchers found that several individual sweeteners were associated with faster declines, particularly in memory-related abilities.

The sweeteners linked with cognitive decline included:

• Aspartame
  
• Saccharin
  
• Acesulfame-K
  
• Erythritol
  
• Sorbitol
  
• Xylitol
  

However, the study found no association between tagatose consumption and cognitive decline.

The researchers cautioned that more studies are needed to understand why some sweeteners appeared linked with cognitive changes while others did not.

Researchers warn: the study does not prove artificial sweeteners cause dementia or memory loss

The authors stressed that the findings should not be interpreted as proof that artificial sweeteners directly damage the brain.

"This study showed a link between the use of some artificial sweeteners and cognitive decline, but it did not prove that they were a cause," researchers noted.

Study author Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo in Brazil, said low- and no-calorie sweeteners are often considered healthier alternatives to sugar, but the findings suggest some may have unexpected effects on long-term brain health.

"Low- and no-calorie sweeteners are often seen as a healthy alternative to sugar, however our findings suggest certain sweeteners may have negative effects on brain health over time," Suemoto said.

Researchers acknowledged that:

• Participants reported their own food and beverage intake, which means some dietary details may have been forgotten or inaccurately recorded.
  
• The study did not include every artificial sweetener available.
  
• Because it was an observational study, researchers could identify patterns but could not prove cause and effect.