A comprehensive study published in the September 3, 2025, issue of Neurology®, the medical journal of the American Academy of Neurology, has identified a significant correlation between the high consumption of low- and no-calorie sweeteners (LNCS) and an accelerated decline in cognitive functions, including memory and thinking skills. Conducted by researchers at the University of São Paulo in Brazil, the longitudinal study tracked nearly 13,000 adults over an eight-year period, revealing that those with the highest daily intake of these substitutes experienced brain aging at a rate significantly faster than those who consumed minimal amounts. While the findings establish a robust statistical link, the researchers emphasized that the study was observational and does not definitively prove that artificial sweeteners are the direct cause of cognitive impairment.
Study Overview and Methodology
The research, led by Claudia Kimie Suemoto, MD, PhD, utilized data from a large-scale cohort of 12,772 participants across Brazil. The average age of the participants at the start of the study was 52, placing the majority of the group in the critical "middle-age" window where lifestyle factors begin to exert a more visible influence on long-term neurological health. Over an average follow-up period of eight years, the participants underwent a series of rigorous evaluations to monitor both their dietary habits and their cognitive performance.
To establish a baseline for sweetener consumption, participants completed detailed food frequency questionnaires at the beginning of the study. These questionnaires required individuals to recall their intake of various foods and beverages over the preceding 12 months, specifically focusing on items known to contain artificial sweeteners, such as diet sodas, flavored waters, low-fat yogurts, and sugar-free desserts. Based on this data, the researchers categorized the participants into three distinct tiers:
- Low Consumption Group: Averaging 20 milligrams per day (mg/day).
- Moderate Consumption Group: Representing the middle tier of intake.
- High Consumption Group: Averaging 191 mg/day.
To provide real-world context, the researchers noted that 191 mg of aspartame is roughly equivalent to the amount found in a single 12-ounce can of diet soda. Sorbitol, a sugar alcohol often used in sugar-free candies and gums, was found to be the most consumed sweetener among the cohort, with an average intake of 64 mg/day.
Cognitive Assessment and Findings
To track the progression of cognitive health, the study utilized a battery of standardized neuropsychological tests administered at the start, middle, and conclusion of the eight-year period. These tests were designed to measure several domains of brain function, including:
- Verbal Fluency: The ability to retrieve information from memory and produce speech efficiently.
- Working Memory: The capacity to hold and manipulate information over short periods.
- Word Recall: A measure of episodic memory and the ability to form new memories.
- Processing Speed: The time taken to respond to and process mental tasks.
After adjusting for confounding variables such as age, biological sex, smoking status, physical activity, and pre-existing conditions like hypertension and cardiovascular disease, the results showed a clear trend. Participants in the highest consumption group (191 mg/day) exhibited an overall cognitive decline that was 62% faster than those in the lowest consumption group. The researchers calculated that this accelerated decline is biologically equivalent to approximately 1.6 additional years of brain aging. Even those in the moderate consumption group were not immune, showing a 35% faster decline compared to the lowest group, which translates to roughly 1.3 years of premature cognitive aging.
Specific Sweeteners and Demographic Variations
The study examined seven specific sweeteners: aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose. With the exception of tagatose, all of these substances were associated with faster declines in overall cognition, with the most pronounced effects observed in memory-related tasks.
The data also revealed significant demographic disparities in how these sweeteners affected the brain. Notably, the link between high sweetener intake and cognitive decline was much stronger in participants under the age of 60. In contrast, the researchers did not find a statistically significant link in participants who were already over the age of 60 at the start of the study. This suggests that the middle-age years may be a "window of vulnerability" where the brain is particularly susceptible to the metabolic or chemical influences of sugar substitutes.
Furthermore, the study highlighted a concerning trend among individuals with diabetes. This group showed a significantly stronger correlation between sweetener use and cognitive decline than those without the condition. Because people with diabetes are often encouraged to avoid refined sugars, they frequently turn to artificial sweeteners as a primary alternative, potentially putting them at higher risk for the neurological side effects observed in this study.
Contextual Background: The Rise of Ultra-Processed Foods
The findings come at a time of increasing global scrutiny regarding ultra-processed foods (UPFs), which serve as the primary delivery vehicle for artificial sweeteners. In the last two decades, the global food supply has shifted toward highly engineered products designed for shelf stability and low-calorie counts. While these products are often marketed as "healthy" or "diet-friendly" alternatives to sugar-laden goods, recent nutritional science has begun to question the "healthy halo" surrounding them.
Artificial sweeteners like aspartame and acesulfame-K are hundreds of times sweeter than sucrose, leading some researchers to hypothesize that they may overstimulate sweet taste receptors. This overstimulation could potentially disrupt the body’s natural metabolic signaling, affecting how the brain perceives satiety and glucose regulation. Additionally, sugar alcohols like erythritol and xylitol have recently been the subject of separate studies investigating their impact on cardiovascular health and blood clotting, adding to a growing body of evidence that "zero-calorie" does not necessarily mean "zero-risk."
Chronology of the Research
The study’s publication in 2025 is the culmination of nearly a decade of data collection and analysis:
- 2015–2017: Initial enrollment of the 12,772 participants. Baseline cognitive testing and dietary questionnaires were completed.
- 2019–2021: Mid-point assessments were conducted to track early changes in cognitive trajectories and monitor shifts in dietary patterns.
- 2023–2024: Final cognitive testing rounds were completed. Researchers began the complex process of adjusting data for cardiovascular health markers and socioeconomic factors.
- Late 2024: Preliminary findings were reviewed by the Brazilian Ministry of Health and the National Council for Scientific and Technological Development.
- September 3, 2025: Full study results published in Neurology®.
Official Responses and Expert Analysis
The lead author, Dr. Claudia Kimie Suemoto, highlighted the public health paradox presented by these findings. "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," she stated. Suemoto urged caution, particularly for those using these substitutes to manage weight or blood sugar, suggesting that more research is needed into natural alternatives like honey, maple syrup, or even unsweetened fruit purees like applesauce.
While the study was supported by major Brazilian governmental bodies, including the Ministry of Science, Technology, and Innovation, independent experts have noted its limitations. One primary concern is the reliance on self-reported dietary data. Participants may suffer from "recall bias," where they inaccurately remember the frequency or quantity of their sweetener consumption. Furthermore, the study did not account for every type of sweetener available on the market, such as stevia or monk fruit, which are increasingly popular in the "natural" sweetener segment.
Neurologists not involved in the study have pointed out that the 62% faster decline is a "striking" figure that warrants immediate attention in clinical settings. However, they also noted the possibility of "reverse causality"—the idea that individuals who are already experiencing the early, subtle stages of cognitive decline might change their diets toward "healthier" sugar-free options, thereby skewing the data.
Broader Implications and Public Health Policy
The implications of this study extend beyond individual dietary choices to the realm of public health policy and food regulation. If further research confirms that even moderate amounts of artificial sweeteners (equivalent to one diet soda per day) can accelerate brain aging by 1.6 years, regulatory agencies may face pressure to update labeling requirements.
Currently, the World Health Organization (WHO) has issued conditional guidelines suggesting that non-sugar sweeteners should not be used as a means of achieving weight control or reducing the risk of non-communicable diseases. The findings from the University of São Paulo provide further evidence to support a more cautious approach to LNCS consumption.
For the general public, the study serves as a reminder that the long-term neurological impacts of food additives are still being mapped. As the prevalence of neurodegenerative diseases like Alzheimer’s continues to rise globally, identifying modifiable risk factors in middle age remains a top priority for medical science. The researchers conclude that while sugar reduction is essential for metabolic health, replacing it with synthetic chemicals may involve a trade-off with cognitive longevity that many consumers are not yet aware of. Future studies are expected to focus on the biological mechanisms—such as gut microbiome alterations or systemic inflammation—that could explain how these chemicals interact with the human brain over decades of use.