According to research published in Neurologythe medical journal of the American Academy of Neurology.
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 their 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
The researchers studied aspartame, saccharin, acesulfame K, erythritol, xylitol, sorbitol and tagatose.
These ingredients are frequently added to ultra-processed products, such as flavored waters, soft drinks, energy drinks, yogurts, 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 considered a healthy alternative to sugar; however, our findings suggest that 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 throughout Brazil. The participants were an average of 52 years old and were monitored for approximately eight years.
At the beginning of the study, participants completed detailed dietary questionnaires describing what they had eaten and drank over the previous year. The researchers then classified them into three groups based on their total sweetener intake.
People in the lowest 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 approximately equal to the aspartame in a can of diet soda.
Sorbitol was consumed in greater quantities than any single sweetener, with an average daily intake of 64 mg/day.
Participants completed cognitive assessments at the beginning, middle, and end of the study. The tests measured several aspects of brain function, including verbal fluency, working memory, word retrieval, and processing speed.
Verbal fluency refers to the ability to retrieve and produce words quickly. Working memory is the brain’s short-term system for retaining 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 taking into account age, sex, high blood pressure, cardiovascular disease and other relevant factors, the researchers found a clear difference between the intake groups.
People who consumed higher amounts of sweeteners experienced a 62% faster decline in their overall thinking and memory abilities than those who consumed less. The researchers estimated that this difference was comparable to about 1.6 additional years of aging.
Participants in the medium consumption group experienced a decline that was 35% faster than the decline seen in the lowest group. That difference was comparable to about 1.3 years of aging.
Stronger association in adults under 60 years of age
Age seemed to influence the results. Among participants under age 60, those who consumed the most sweeteners experienced more rapid declines in verbal fluency and overall cognitive performance than those who consumed the least.
The researchers did not find the same association among participants over 60 years old.
The connection between sweetener intake and faster cognitive decline was also stronger among people with diabetes than among those without the disease. People with diabetes may use sugar substitutes more often because they are often advised to limit products that quickly raise blood sugar.
Six sweeteners linked to changes in memory
When the researchers examined the sweeteners separately, six were associated with more rapid 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.
“Although we found links to cognitive decline in middle-aged people 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 investigate whether other alternatives to refined sugar, such as applesauce, honey, maple syrup or coconut sugar, may be effective alternatives.”
Important limits of the research
The study did not include all artificial sweeteners currently used in foods and beverages, so the findings cannot be applied to all sugar substitutes.
Dietary information was also provided by the participants themselves. Because people may forget foods or misjudge the amount they consumed, self-reported dietary data may be imperfect.
The most important thing is that the study was observational. It identified a relationship between higher sweetener consumption and faster cognitive decline, but could not establish that sweeteners caused those changes.
Key findings
- The study followed 12,772 adults with an average age of 52 years.
- The 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 more rapid 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 under 60 years of age, but was not detected in those over 60 years of age.
- The findings show a link, but 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.