The study followed nearly 13,000 adults and examined seven sweeteners that contain little or no calories. People who consumed the largest total amounts showed a more rapid decline in cognitive abilities than those who consumed the smallest amounts. The association was especially strong among people with diabetes.

The results do not show that sweeteners directly cause cognitive decline. They reveal an association, meaning other factors could help explain the pattern.

Seven Common Sweeteners Examined

Researchers studied aspartame, saccharin, acesulfame K, erythritol, xylitol, sorbitol and tagatose.

These ingredients are frequently added to ultra processed products, including flavored water, soft drinks, energy drinks, yogurt and desserts marketed as low in calories. Several are also sold separately for use in coffee, tea, cooking or baking.

"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," said study author Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo in Brazil.

Tracking Brain Health for Eight Years

The research included 12,772 adults living across Brazil. Participants were 52 years old on average and were monitored for approximately eight years.

At the beginning of the study, participants completed detailed food questionnaires describing what they had eaten and drunk during the previous year. Researchers then placed them into three groups according to their total sweetener intake.

People in the lowest consumption group averaged 20 milligrams per day (mg/day), while those in the highest group averaged 191 mg/day. In the case of aspartame, the amount consumed by the highest group was roughly equal to the aspartame in one can of diet soda.

Sorbitol was consumed in the largest quantity of any individual sweetener, with an average daily intake of 64 mg/day.

Participants completed cognitive assessments at the beginning, midpoint and end of the study. The tests measured several aspects of brain function, including verbal fluency, working memory, word recall and processing speed.

Verbal fluency refers to the ability to quickly retrieve and produce words. Working memory is the brain's short term system for holding and using information, while processing speed reflects how quickly a person can understand and respond to information.

Higher Intake Linked to Faster Cognitive Decline

After accounting for age, sex, high blood pressure, cardiovascular disease and other relevant factors, the researchers found a clear difference between the intake groups.

People who consumed the greatest amounts of sweeteners experienced a 62% faster decline in overall thinking and memory abilities than those who consumed the least. Researchers estimated that this difference was comparable to about 1.6 additional years of aging.

Participants in the middle consumption group experienced a decline that was 35% faster than the decline observed in the lowest group. That difference was comparable to approximately 1.3 years of aging.

Stronger Association in Adults Under 60

Age appeared to influence the results. Among participants younger than 60, those who consumed the most sweeteners experienced faster declines in verbal fluency and overall cognitive performance than those who consumed the least.

Researchers did not find the same association among participants older than 60.

The connection between sweetener intake and faster cognitive decline was also stronger among people with diabetes than among those without the condition. People with diabetes may use sugar substitutes more frequently because they are often advised to limit products that rapidly raise blood sugar.

Six Sweeteners Linked to Memory Changes

When the researchers examined the sweeteners separately, six were associated with faster declines in overall cognition, particularly memory.

Those sweeteners were aspartame, saccharin, acesulfame K, erythritol, sorbitol and xylitol.

Tagatose was the only sweetener in the study that was not linked to cognitive decline.

"While we found links to cognitive decline for middle-aged people both with and without diabetes, people with diabetes are more likely to use artificial sweeteners as sugar substitutes," Suemoto said. "More research is needed to confirm our findings and to investigate if other refined sugar alternatives, such as applesauce, honey, maple syrup or coconut sugar, may be effective alternatives."

Important Limits of the Research

The study did not include every artificial sweetener currently used in food and beverages, so the findings cannot be applied to all sugar substitutes.

The dietary information was also provided by the participants themselves. Because people may forget foods or misjudge how much they consumed, self reported diet data can be imperfect.

Most importantly, the study was observational. It identified a relationship between higher sweetener consumption and faster cognitive decline, but it could not establish that the sweeteners caused those changes.

Key Findings

• The study followed 12,772 adults with an average age of 52.
• Researchers examined seven sweeteners commonly found in flavored water, soda, energy drinks, yogurt, low calorie desserts and other ultra processed foods.
• Participants who consumed the largest total amounts experienced faster declines in overall thinking and memory skills than those who consumed the smallest amounts.
• The difference was comparable to approximately 1.6 additional years of aging.
• The association appeared in adults younger than 60 but was not detected in those older than 60.
• The findings show a link, but they do not prove that sugar substitutes cause cognitive decline.

The research was supported by the Brazilian Ministry of Health, the Ministry of Science, Technology, and Innovation, and the National Council for Scientific and Technological Development.