The investigation focused on seven of the most common artificial and semi-synthetic sweeteners currently approved for use in the global food supply: aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose. These substances are pervasive in modern diets, primarily serving as key ingredients in ultra-processed foods such as diet sodas, flavored waters, energy drinks, low-fat yogurts, and sugar-free desserts. As the global prevalence of metabolic disorders like obesity and diabetes has risen, these substitutes have been marketed as healthier alternatives to refined sugar; however, this latest data raises critical questions regarding their long-term impact on neurological health.
Methodology and Study Demographics
The research was led by Dr. Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo in Brazil, and involved a diverse cohort of 12,772 adults. The average age of the participants at the start of the study was 52, placing the majority in the middle-aged demographic where early signs of cognitive aging typically begin to manifest. The longitudinal nature of the study allowed researchers to follow these individuals for an average of eight years, providing a substantial window to observe changes in brain health.
At the onset of the study, participants were required to complete detailed dietary questionnaires. These assessments covered food and beverage consumption over the preceding 12 months, allowing researchers to calculate the average daily intake of specific sweeteners. Based on this data, the cohort was divided into three distinct groups:
- The Lowest Consumption Group: Averaging 20 milligrams per day (mg/day).
- The Middle Consumption Group: Averaging a moderate intake between the high and low extremes.
- The Highest Consumption Group: Averaging 191 mg/day.
To put these numbers into a practical context, the researchers noted that the high-consumption threshold of 191 mg/day for aspartame is roughly equivalent to the amount found in a single 12-ounce can of diet soda. Among the sweeteners studied, sorbitol—a sugar alcohol often found in sugar-free gums and candies—had the highest average consumption rate among participants, at approximately 64 mg/day.
Measuring Cognitive Performance
To track the progression of brain health, the research team administered a battery of standardized cognitive tests at three specific intervals: the beginning, the midpoint, and the conclusion of the eight-year study period. These evaluations were designed to measure a broad spectrum of neurological capabilities, including:
- Verbal Fluency: The ability to retrieve information quickly from memory.
- Working Memory: The capacity to hold and manipulate information over short periods.
- Word Recall: A primary indicator of episodic memory and hippocampal health.
- Processing Speed: The time it takes for the brain to receive, understand, and respond to information.
By analyzing the delta between the initial and final test scores, researchers could determine the rate of "cognitive aging" for each participant relative to their dietary habits.
Analysis of Results: The Aging Gap
The findings revealed a stark disparity in cognitive trajectories based on sweetener intake. After adjusting for confounding variables such as age, sex, education level, smoking status, and physical activity—as well as clinical factors like high blood pressure and cardiovascular disease—the data showed that those in the highest consumption group experienced an overall cognitive decline that was 62% faster than those in the lowest group.
According to the research team, a 62% acceleration in decline is clinically significant, representing the equivalent of approximately 1.6 years of additional brain aging over the study’s eight-year duration. Even those in the middle consumption group were not immune; they exhibited a decline that was 35% faster than the low-intake group, roughly equivalent to 1.3 years of accelerated aging.
"Low- and no-calorie sweeteners are often seen as a healthy alternative to sugar, particularly for those managing weight or blood glucose," said Dr. Suemoto. "However, our findings suggest certain sweeteners may have negative effects on brain health over time. This is particularly concerning given the ubiquity of these substances in the modern food environment."
Age and Health Specificity
The study provided nuanced insights into which populations might be most vulnerable. Interestingly, when the data was segmented by age, the link between high sweetener consumption and cognitive decline was most pronounced in participants under the age of 60. In this younger demographic, high intake was specifically associated with poorer performance in verbal fluency and overall global cognition. Conversely, the researchers did not find a statistically significant link in participants who were already over the age of 60 at the study’s inception.
Furthermore, the association was notably stronger in individuals diagnosed with diabetes. This is a critical finding because people with diabetes are among the most frequent consumers of artificial sweeteners, often using them to manage insulin levels while satisfying a preference for sweet tastes. The study suggests that for this high-risk group, the very tools used to manage metabolic health might potentially be contributing to a secondary health crisis in the form of accelerated neurodegeneration.
Individual Sweetener Profiles
While the study looked at the cumulative effect of sweeteners, it also examined the impact of individual substances. The data indicated that the consumption of aspartame, saccharin, acesulfame-K, erythritol, sorbitol, and xylitol were all individually associated with faster declines in global cognition and memory.
Of particular note was the absence of a link regarding tagatose. Tagatose, a rare sugar that is naturally occurring but often produced commercially, showed no association with cognitive decline in this study. This outlier provides a potential avenue for future research into whether certain "rare sugars" might be safer for neurological health than traditional high-intensity artificial sweeteners.
Historical Context and Scientific Backdrop
The findings from the University of São Paulo add to a growing body of evidence questioning the long-term safety of non-sugar sweeteners (NSS). In May 2023, the World Health Organization (WHO) released a guideline advising against the use of NSS for weight control, citing potential increased risks of type 2 diabetes and cardiovascular diseases. This followed decades of "diet culture" that promoted these chemicals as a "free pass" for consumers.
Earlier in 2024 and 2025, other independent studies raised alarms about erythritol and xylitol, linking high blood levels of these sugar alcohols to an increased risk of heart attack and stroke due to their potential effect on blood platelet reactivity. The Neurology® study expands this concern from the cardiovascular system to the central nervous system, suggesting a systemic impact of these compounds.
Implications and Professional Responses
The medical community has reacted to the study with a mixture of caution and a call for increased scrutiny. Nutritionists have long debated the "ultra-processed food" (UPF) effect, arguing that it is difficult to isolate the impact of a single sweetener when it is usually consumed as part of a chemical-heavy diet.
"While this study is robust in its scale, we must consider the ‘cocktail effect’ of ultra-processed foods," noted one independent dietitian not involved in the study. "However, the 62% figure is a loud signal that we cannot ignore. It suggests that our attempts to bypass the caloric consequences of sugar may be coming at a neurological cost."
Dr. Suemoto echoed the need for broader dietary considerations. "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 and safer alternatives for long-term health," she stated.
Limitations and Future Directions
Despite the compelling data, the researchers acknowledged several limitations. The study relied on self-reported dietary information, which is subject to recall bias—participants may not have accurately remembered or reported every food item consumed. Additionally, while the study covered seven major sweeteners, it did not include newer or less common alternatives like stevia or monk fruit, leaving a gap in the understanding of the full sweetener landscape.
The geographical focus on Brazil, while providing a large and diverse sample, may also reflect specific regional dietary patterns that might differ from those in North America or Europe, though the types of ultra-processed foods consumed are largely globalized brands.
Conclusion and Public Health Outlook
The study, supported by the Brazilian Ministry of Health and the National Council for Scientific and Technological Development, serves as a significant milestone in nutritional neuroscience. As cognitive disorders like Alzheimer’s disease continue to rise globally, identifying modifiable risk factors in midlife is a top priority for public health officials.
The evidence presented in Neurology® suggests that for middle-aged adults, particularly those under 60 and those with diabetes, the habitual use of artificial sweeteners could be a hidden accelerator of brain aging. As the scientific community awaits further clinical trials to establish causality, the current data suggests that a return to whole, unprocessed foods and a reduction in the reliance on chemical sugar substitutes may be a prudent strategy for preserving cognitive longevity.
