Several widely used sugar substitutes may be linked to a faster decline in memory and cognitive abilities over time. This is according to a study published in *Neurology*, the journal of the American Academy of Neurology.
The study tracked nearly 13,000 adults and examined seven sweeteners that contain few or no calories. Participants who consumed the highest total amounts showed a faster decline in cognitive abilities than those who consumed the lowest amounts. The association was particularly pronounced among people with diabetes. The results do not prove that sweeteners directly cause cognitive decline. They merely indicate an association, which means that other factors could contribute to this pattern.
Seven Common Sweeteners Under the Microscope
In the study, the researchers examined seven sugar substitutes used in many low-calorie foods and beverages: aspartame, saccharin, acesulfame K, erythritol, xylitol, sorbitol, and tagatose. These substances differ in their chemical structure, sweetness, and effects on the body.
Aspartame is one of the best-known artificial sweeteners. It is about 200 times sweeter than table sugar and is frequently used in sugar-free beverages, chewing gum, confectionery, and “light” products. In the European Union, aspartame is approved as food additive E951 and has been evaluated by regulatory authorities for safety.
Saccharin is one of the oldest artificial sweeteners and is about 300 to 500 times sweeter than sugar. It is used, among other things, in beverages, confectionery, and as a tabletop sweetener. Saccharin contains no calories and is excreted by the body largely unchanged.
Acesulfame-K (acesulfame potassium) is a calorie-free sweetener with a sweetness about 200 times that of sugar. It is often used in combination with other sweeteners, for example in soft drinks, desserts, or dairy products, as it can enhance the sweetness of other substances.
Erythritol, xylitol, and sorbitol are among the so-called sugar alcohols (polyols). Some of them also occur naturally in fruits and plants. They contain fewer calories than sugar and are frequently used in sugar-free candies, chewing gum, baked goods, and diet products. Large amounts can cause digestive problems such as bloating or diarrhea in some people.
Tagatose is a rarely used sugar substitute that is chemically related to fructose. It has a sweetness similar to that of sugar but provides significantly fewer calories. In the study, tagatose was the only one of the seven substances examined for which no association with accelerated cognitive decline was found.
The sweeteners examined are found today in numerous products marketed as low-calorie or sugar-free—including flavored water, soft drinks, energy drinks, yogurt, desserts, and confectionery. Some are also sold directly as table sweeteners or for cooking and baking. “Low-calorie and calorie-free sweeteners are often viewed as a healthier alternative to sugar. However, our findings suggest that certain sweeteners may be associated with changes in brain health over the long term,” explained study author Dr. Claudia Kimie Suemoto of the University of São Paulo. The researchers emphasize, however, that further studies are needed to determine whether a causal relationship actually exists.
Brain Health Was Monitored for Eight Years
The study included 12,772 adults from across Brazil. The participants were 52 years old on average and were followed for approximately eight years. At the start of the study, participants completed detailed dietary questionnaires in which they reported what they had eaten and drunk over the past year. The researchers then divided them into three groups based on their total intake of sweeteners.
Participants in the group with the lowest consumption averaged 20 milligrams per day (mg/day), while those in the group with the highest consumption averaged 191 mg/day. In the case of aspartame, the amount consumed by the group with the highest intake was roughly equivalent to the aspartame content of one can of diet soda.
Of all the individual sweeteners, sorbitol was consumed in the greatest amount, with an average daily intake of 64 mg/day. The participants took cognitive tests at the beginning, middle, and end of the study. The tests measured various 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 memory system that stores and uses information, while processing speed reflects how quickly a person can understand and respond to information.
Higher Consumption is Associated with Faster Cognitive Decline
After the researchers accounted for various factors such as age, gender, high blood pressure, cardiovascular disease, and other health factors, a difference emerged between the groups with varying levels of sweetener consumption.
Participants who consumed the highest amounts of sweeteners showed a significantly faster decline in their cognitive abilities during the observation period than those with the lowest consumption. These abilities included, among others, memory, rapid information processing, and language skills.
The difference was approximately 62 percent compared to the group with the lowest consumption. The researchers estimated this difference to be equivalent to about 1.6 additional years of age-related cognitive decline. This does not mean that the participants lost their mental abilities within a short period of time, but rather that the decline progressed somewhat more rapidly over the years. Even individuals with moderate sweetener consumption showed a faster decline than the group with the lowest consumption. Here, the difference was about 35 percent, which the researchers compared to roughly 1.3 additional years of cognitive aging.
The results show a statistical association between higher sweetener consumption and changes in cognitive function. However, they do not prove that sweeteners are the cause. It is also possible that other factors—such as overall diet, health status, or conditions like diabetes—may influence this association.
Not Everyone Was Affected to the Aame Degree
The researchers found that the participants’ age appeared to play a role in the results. Particularly among adults under 60, there was a link between high sweetener consumption and a faster decline in certain cognitive abilities.
Verbal fluency and general cognitive performance were particularly affected. Verbal fluency refers to the ability to retrieve appropriate words quickly and respond with linguistic flexibility. This ability can provide insight into how well different areas of the brain work together. In contrast, the researchers found no comparable association among participants over the age of 60. Why this difference between the age groups emerged remains unclear. Age-related changes in metabolism, vascular health, or other factors may play a role.
Among people with diabetes, the association between higher sweetener consumption and faster cognitive decline was also more pronounced. One possible explanation is that people with diabetes are more likely to use sugar substitutes because they are advised to reduce their consumption of sugar and foods high in sugar. At the same time, the researchers point out that diabetes itself may be a known risk factor for changes in brain health. Therefore, it is not possible to conclusively determine from the results whether the sweeteners, the disease of diabetes, or other associated factors influence the observed association.
Six Sweeteners are Linked to Changes in Memory
In addition to examining total sweetener consumption, the researchers also analyzed the individual sugar substitutes separately. They found that six of the seven substances studied were associated with a more rapid decline in cognitive function. These sweeteners included aspartame, saccharin, acesulfame K, erythritol, sorbitol, and xylitol. Areas such as memory and other mental abilities—which play a role in everyday life, for example, in learning, recalling information, or processing information quickly—were particularly affected.
In this study, the researchers found no link between tagatose and accelerated cognitive decline. However, this does not mean that tagatose generally has a protective effect on the brain. The results merely show that no statistical association was found in this study.
Study author Dr. Claudia Kimie Suemoto emphasized that the findings were primarily observed in middle-aged adults with and without diabetes. However, the results do not clearly indicate whether the sweeteners, diabetes itself, or other related factors are responsible for the observed association. “Further research is needed to confirm our findings,” Suemoto explained. Future studies must also clarify whether certain alternatives to refined sugar—such as natural sweeteners or unprocessed foods—actually offer health benefits or whether other factors explain the association.
Important Limitations of the Study
The study did not include all artificial sweeteners currently used in foods and beverages, so the results cannot be generalized to all sugar substitutes. Furthermore, dietary information was self-reported by the participants. Since people may forget certain foods or misjudge the amounts they consume, self-reported dietary data may be incomplete. Above all, however, this was an observational study. While it identified an association between higher consumption of sweeteners and faster cognitive decline, it could not prove that the sweeteners caused these changes.