Popular Sugar Substitutes Linked to Faster Cognitive Decline

A long-term study of Brazilian adults found that higher intake of several widely used artificial sweeteners was linked to faster cognitive decline, especially in people under 60 and those with diabetes.

Swapping sugar for artificial sweeteners is often framed as an easy health win, but a large new study suggests the story may be more complicated for the brain. Researchers reporting in Neurology, the medical journal of the American Academy of Neurology, found that heavier use of certain sugar substitutes was tied to a faster drop in memory and thinking over time. The pattern was strongest among people with diabetes.

The study does not show that sweeteners directly damage the brain. Instead, it highlights an association that remained even after researchers accounted for major health factors that can affect cognition.

The team looked at seven widely used sweeteners: aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose. These ingredients show up most often in ultra-processed foods and drinks such as flavored water, soda, energy drinks, yogurt, and low-calorie desserts, and some are also sold as standalone sweeteners.

“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.

Study Design and Participant Details

To explore long-range effects, the researchers followed 12,772 adults from across Brazil for about eight years. Participants were 52 years old on average.

At the start, participants completed detailed diet questionnaires covering what they ate and drank over the prior year. Researchers then grouped people based on how much total artificial sweetener they consumed. The lowest intake group averaged 20 milligrams per day (mg/day). The highest intake group averaged 191 mg/day, which for aspartame is about the amount found in one can of diet soda. Among the individual sweeteners, sorbitol stood out with the highest average intake at 64 mg/day.

Participants also took cognitive tests at the beginning, middle, and end of the study. These assessments tracked several skills that tend to change with aging and brain health, including how quickly someone can find words, how well they can hold information in mind, how easily they can recall words later, and how fast they process information.

After adjusting for factors such as age, sex, high blood pressure and cardiovascular disease, the researchers found that the highest intake group declined 62% faster in overall thinking and memory than the lowest intake group. The difference was roughly comparable to about 1.6 years of aging. The middle intake group also declined faster than the lowest intake group, with a 35% faster drop, about the equivalent of 1.3 years of aging.

Differences by Age and Diabetes Status

When the data were analyzed by age, a clearer pattern emerged among participants younger than 60. In this group, those who consumed the most sweeteners experienced steeper drops in verbal fluency and overall cognitive performance compared with those who consumed the least. No significant association was observed among adults older than 60.

The relationship between sweetener intake and cognitive decline was also stronger in participants with diabetes than in those without the condition.

Looking at individual sweeteners, higher consumption of aspartame, saccharin, acesulfame-k, erythritol, sorbitol and xylitol was linked to faster declines in overall cognitive function, especially memory. Tagatose was the only sweetener studied that did not show an association with 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.”

The authors noted several limitations. The analysis did not cover every type of artificial sweetener available. In addition, dietary information was self-reported, meaning participants may not have recalled their food and beverage intake with complete accuracy.

References:

“Association Between Consumption of Low- and No-Calorie Artificial Sweeteners and Cognitive DeclineAn 8-Year Prospective Study” by Natalia Gomes Gonçalves, Euridice Martinez-Steele, Paulo A. Lotufo, Isabela Bensenor, Alessandra C. Goulart, Sandhi Maria Barreto, Luana Giatti, Carolina Perim de Faria, Maria del Carmen Bisi Molina, Paulo Caramelli, Dirce Maria Marchioni and Claudia Kimie Suemoto, 3 September 2025, Neurology.

“The Dark Side of Sweet: Neurocognitive Consequences of Artificial Sweeteners” by Thomas Monroe Holland, 3 September 2025, Neurology.

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

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