Sugar substitutes have long been promoted as a healthier way to enjoy sweet foods and drinks without consuming the high amounts of calories and sugar associated with traditional sweeteners. For decades, individuals looking to manage their weight, cut back on empty calories, or control blood sugar levels have turned to diet sodas, flavored waters, and various low-calorie packaged foods. However, new research suggests that some of these widely used artificial sweeteners and sugar alternatives may carry an unexpected downside for long-term brain health, raising fresh questions about their overall safety and efficacy.
A study published in Neurology, the prominent medical journal of the American Academy of Neurology, has found that people who consumed the highest amounts of low- and no-calorie sweeteners experienced significantly faster declines in memory and thinking skills compared to those who consumed the least. Crucially, this association was particularly pronounced among individuals living with diabetes, a demographic that frequently relies on sugar substitutes to navigate dietary restrictions.
Researchers examined seven distinct sweeteners commonly found in modern food and beverage supplies: aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose. These ingredients frequently appear on ingredient lists in ultra-processed products, including diet sodas, flavored waters, energy drinks, yogurts, and low-calorie desserts. Additionally, many of these substances are sold separately as tabletop packets for sweetening coffee, tea, and other foods and beverages at home.
"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, an associate professor and researcher at the University of São Paulo in Brazil.
Despite the concerning trend revealed in the data, researchers emphasized an important caveat: the findings show an association rather than a proven cause-and-effect relationship. Based strictly on this observational study, scientists cannot definitively conclude that consuming these sweeteners directly damages the brain or actively causes memory loss. Nevertheless, the strength of the statistical link has drawn significant attention from the medical and scientific communities, prompting calls for more thorough investigations into how these chemical compounds interact with the human body over prolonged periods.
Study Tracks Nearly 13,000 Adults for Eight Years
To investigate whether popular sugar substitutes might be connected to long-term cognitive health, an international team of researchers analyzed comprehensive data gathered from 12,772 adult participants across Brazil. At the beginning of the research project, the participants had an average age of 52 years, placing them firmly in middle age, a critical window for observing early indicators of cognitive aging. The cohort was then followed for an average period of approximately eight years, allowing researchers to track subtle shifts in mental acuity over time.
At the onset of the study, participants completed detailed and extensive dietary questionnaires describing the various foods and drinks they had consumed during the previous year. Using these detailed personal responses, researchers calculated and estimated each person’s daily intake of the seven target sweeteners.
To make sense of the vast range of consumption levels, participants were divided into three distinct groups based on how much of the sweeteners they consumed daily. Those placed in the lowest consumption group averaged a modest 20 milligrams per day (mg/day). In contrast, participants in the highest consumption group averaged a much more substantial 191 mg/day. To put these figures into a practical perspective, 191 milligrams of aspartame is roughly equivalent to the amount found in just a single standard can of diet soda.
Among all seven sweeteners examined in the project, sorbitol recorded the highest average intake among participants, coming in at 64 mg/day. Sorbitol belongs to a broader category of sugar substitutes known as sugar alcohols, or polyols, which provide a sweet flavor profile and are frequently used in sugar-free chewing gums, baked goods, and various diet foods.
Throughout the multi-year duration of the study, participants were periodically evaluated through structured cognitive assessments administered at three specific milestones: the beginning, middle, and end of the tracking period. These standardized tests were specifically designed to measure several cognitive abilities essential for everyday mental functioning, including memory, linguistic capabilities, and the speed at which the human brain processes complex information.
The evaluations tested verbal fluency, which measures a person’s ability to quickly retrieve and produce words from their memory, alongside working memory, the cognitive system responsible for temporarily holding and manipulating information needed for complex tasks. Researchers also tested word recall and processing speed to determine precisely how these mental faculties evolved and potentially degraded over the course of the eight-year study.
High Sweetener Consumption Linked to 62% Faster Cognitive Decline
The analytical results revealed a striking and statistically significant difference in cognitive trajectories between people who consumed the highest levels of sweeteners and those who consumed the least.
After carefully adjusting and accounting for a wide array of potential confounding factors that could independently influence cognitive health—including age, sex, high blood pressure, and underlying cardiovascular disease—researchers found a clear divergence. Participants in the highest sweetener consumption group experienced a 62% faster decline in overall thinking and memory abilities compared with their peers in the lowest consumption group.
To help translate these statistical percentages into understandable human terms, researchers noted that this rate of decline was equivalent to approximately 1.6 additional years of cognitive aging over the course of the study period.
Importantly, the data indicated that heavy consumption was not the only threshold associated with measurable neurological changes. Even moderate consumption was linked to observable differences in cognitive scores. Participants who fell into the middle consumption group experienced a 35% faster decline in cognitive performance than those consuming the least, an effect equivalent to roughly 1.3 additional years of cognitive aging.
Researchers were quick to clarify that these estimates describe relative changes in performance on standardized cognitive tests over time rather than a direct biological measurement of physical brain aging. Furthermore, the findings do not imply that every individual who consumes artificial sweeteners will automatically experience memory problems or cognitive impairment.
Stronger Links Found in Adults Under 60 and People With Diabetes
When the research team broke down the data to examine different age brackets and health profiles, they discovered that the association between sweeteners and cognitive decline was not uniformly distributed across all participants.
Among adults younger than 60 years old, higher sweetener consumption was robustly linked to faster declines in verbal fluency and overall cognitive performance. Interestingly, researchers did not find a similar statistical association among participants who were older than 60, suggesting that middle-aged adults may be particularly vulnerable to the neurological impacts of these substances, or that other age-related cognitive factors begin to overshadow dietary influences later in life.
Furthermore, the relationship between sweetener intake and cognitive decline was notably stronger in individuals diagnosed with diabetes compared to those without the condition. This specific finding carries considerable public health relevance, given that people with diabetes frequently turn to low- and no-calorie sugar substitutes as a primary strategy to help manage their blood sugar levels and control carbohydrate intake.
When the researchers examined the seven individual substances separately to see if certain sweeteners drove the results, they discovered that six of the seven were independently associated with faster declines in overall cognitive performance, with memory being particularly affected. Those six widely used substances were aspartame, saccharin, acesulfame-K, erythritol, sorbitol, and xylitol.
Tagatose stood out as the sole exception among the group. Researchers found no statistically significant association between tagatose consumption and cognitive decline in this particular study. However, the scientific team cautioned that this finding does not establish that tagatose actively protects the brain or that it is inherently safer than other sugar substitutes; rather, it simply means no clear link was observed within this specific cohort.
Should People Rethink Artificial Sweeteners?
The publication of these findings raises complex and important questions regarding whether replacing refined sugar with low-calorie alternatives always delivers the straightforward health benefits that consumers expect, particularly when it comes to long-term neurological health and brain function.
"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," Dr. Suemoto noted, emphasizing the need for caution and continued scientific inquiry. "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 study’s authors also acknowledged several inherent limitations within their methodology. For instance, the analysis did not encompass every single artificial sweetener and sugar substitute currently available on the commercial market, meaning the results cannot be universally applied to every alternative sweetener in existence.
In addition, the dietary information relied heavily on participants’ retrospective recollections of what they had eaten and drunk over the previous year. Because human memory is imperfect—leading individuals to occasionally forget specific foods, underestimate portion sizes, or inaccurately report their daily dietary habits—these estimates may not perfectly reflect absolute, real-world sweetener consumption.
The observational design of the study also leaves open the possibility that other unmeasured lifestyle or dietary factors could help explain the observed relationship between sweetener intake and cognitive decline, despite researchers’ rigorous efforts to control for major health and demographic variables.
Moving forward, further scientific studies will be required to determine whether the sweeteners themselves directly contribute to biochemical changes in brain function, why certain demographic groups appear more strongly affected than others, and whether different natural or synthetic sugar alternatives produce distinctly different long-term health outcomes.
The research was financially supported by key Brazilian scientific and governmental institutions, including the Brazilian Ministry of Health, the Ministry of Science, Technology, and Innovation, and the National Council for Scientific and Technological Development.
