Sugar substitutes are often touted as a healthier way to enjoy sweet foods and drinks without consuming as much sugar. However, new research suggests that some of these widely used sweeteners may have unexpected downsides for long-term brain health.
A study published in Neurologythe medical journal of the American Academy of Neurology, found that people who consumed the most low- or no-calorie sweeteners experienced a significantly faster decline in memory and thinking skills than those who consumed the least. The association was particularly pronounced among people with diabetes.
Researchers looked at seven sweeteners commonly used in foods and drinks: aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol and tagatose. These ingredients frequently appear in ultra-processed products, including diet sodas, flavored waters, energy drinks, yogurts, and low-calorie desserts. Some are also sold separately to sweeten foods and drinks.
“Low- or no-calorie sweeteners are often considered a healthy alternative to sugar; however, our findings suggest that some 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.
It is important to note that the results show an association rather than a proven cause and effect relationship. Researchers cannot conclude from this study that consuming these sweeteners directly damages the brain or causes memory loss.
Study follows nearly 13,000 adults for eight years
To determine whether sugar substitutes might be linked to cognitive health, researchers analyzed data from 12,772 adults across Brazil. Participants were on average 52 years old at the start of the study and were followed for approximately eight years.
At the start of the study, participants completed detailed dietary questionnaires describing the foods and drinks they had consumed over the previous year. The researchers used these responses to estimate each person’s daily consumption of the seven sweeteners.
Participants were then separated into three groups based on the amount of sweeteners they consumed. People in the lowest consumption group consumed an average of 20 milligrams per day (mg/day), while those in the highest group consumed an average of 191 mg/day. For comparison, 191 milligrams of aspartame is roughly the amount found in a can of diet soda.
Of the seven sweeteners examined, sorbitol had the highest average intake, at 64 mg/day. Sorbitol belongs to a category of sweeteners called sugar alcohols, which provide sweetness and are commonly used as sugar substitutes.
Throughout the study, participants completed cognitive assessments at three time points: the beginning, middle, and end. These tests measured several abilities essential to daily mental functioning, including memory, language, and the speed at which the brain processes information.
Researchers assessed verbal fluency, or the ability to quickly retrieve and produce words, as well as working memory, which allows people to temporarily retain and use information. They also tested word memorization and processing speed to determine how these abilities changed over time.
High consumption of sweeteners linked to 62% faster cognitive decline
The results revealed a striking difference between people who consumed the most sweeteners and those who consumed the least.
After accounting for factors likely to influence cognitive health, including age, gender, high blood pressure and cardiovascular disease, the researchers found that participants in the highest consumption group experienced a 62% faster decline in their overall thinking and memory skills compared to those in the lowest group.
This difference equated to approximately 1.6 additional years of cognitive aging over the study period.
Even moderate consumption was associated with measurable differences. Participants in the middle group experienced a 35% faster decline than those who consumed the least, equivalent to about 1.3 additional years of cognitive aging.
These estimates describe changes in cognitive test performance rather than a direct measure of biological brain aging. This also doesn’t mean that everyone who consumes artificial sweeteners will experience memory problems.
Stronger links found in adults under 60 and people with diabetes
When the researchers looked at different age groups, they found that the association was not consistent across all participants.
In adults younger than 60, higher consumption of sweeteners was associated with a faster decline in verbal fluency and overall cognitive performance. However, the researchers did not find a similar association among participants aged over 60.
The relationship was also stronger in people with diabetes than in those without diabetes. This finding is particularly relevant because people with diabetes frequently turn to sugar substitutes to help them manage their sugar intake.
Examining the sweeteners individually revealed another important distinction. Six of the seven substances were associated with a faster decline in overall cognitive performance, particularly memory.
These six were aspartame, saccharin, acesulfame-K, erythritol, sorbitol, and xylitol.
Tagatose was the exception. Researchers found no association between its consumption and cognitive decline in this study. However, this finding does not establish that tagatose protects the brain or that it is necessarily safer than other sweeteners.
Should people rethink artificial sweeteners?
The findings raise important questions about whether replacing sugar with lower-calorie alternatives still provides the health benefits consumers expect, particularly when it comes to the brain.
“Although we found links to cognitive decline in middle-aged people with or without diabetes, people with diabetes are more likely to use artificial sweeteners as sugar substitutes,” Suemoto said. “Additional research is needed to confirm our findings and determine whether other alternatives to refined sugar, such as applesauce, honey, maple syrup, or coconut sugar, may be effective alternatives.”
The researchers also recognized several limitations. The analysis did not cover all artificial sweeteners available on the market, so the results cannot necessarily be applied to all sugar substitutes.
Additionally, dietary information came from participants’ own memories of what they ate and drank. Because people may forget foods, underestimate serving sizes, or inaccurately report their habits, these estimates may not perfectly reflect actual sweetener consumption.
The observational design also means that other factors could help explain the relationship between sweetener consumption and cognitive decline, despite researchers’ efforts to account for several important health differences.
Further studies will be needed to determine whether sweeteners themselves contribute to changes in brain function, why certain groups appear more strongly affected, and whether different alternatives to sugar produce different long-term results.
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.
Gn Health
