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A large prospective study from Brazil, published in Neurology (American Academy of Neurology) on September 3, 2025, found that people who consume high amounts of certain artificial sweeteners show faster declines in memory and thinking abilities over time. Tracking 12,772 adults with an average age of 52 for roughly eight years, researchers observed that the highest consumers experienced cognitive decline equivalent to about 1.6 years of extra brain aging compared with the lowest consumers. The association was strongest in participants under 60 and among people with diabetes.
Study design and primary findings
Researchers collected baseline dietary information from participants using food-frequency questionnaires that covered the previous year. They quantified intake of seven low- and no-calorie sweeteners commonly added to ultra-processed foods and beverages: aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol and tagatose. Participants were grouped into low, middle and high total-intake categories. The lowest group averaged about 20 mg/day of total sweeteners, while the highest averaged 191 mg/day — roughly the amount of aspartame found in a typical can of diet soda. Sorbitol was the most-consumed sweetener on average (about 64 mg/day).
Cognitive testing—administered at baseline, mid-point and end of follow-up—assessed verbal fluency, working memory, word recall and processing speed. After adjusting for age, sex, education, hypertension, cardiovascular disease and other potential confounders, the highest-intake group showed a 62% faster decline in overall cognition than the lowest-intake group, equivalent to about 1.6 years of brain aging. The middle-intake group declined about 35% faster (approximately 1.3 years). When stratified by age, associations were observed in adults younger than 60 but not in those older than 60. People with diabetes showed a stronger link between higher sweetener intake and faster cognitive decline.
When individual sweeteners were examined, aspartame, saccharin, acesulfame-K, erythritol, xylitol and sorbitol were associated with faster overall cognitive decline, particularly in memory-related tests. No association was detected for tagatose.
Scientific context and possible mechanisms
This observational study adds to a growing body of research examining metabolic, vascular and microbiome-related pathways that could connect diet with brain aging. Several, non-mutually exclusive mechanisms are plausible and under investigation:
- Gut-brain axis: Artificial sweeteners can alter the composition and function of the gut microbiome in ways that might influence systemic inflammation and neural processes.
- Metabolic and vascular effects: Some sugar substitutes change glucose metabolism or insulin signaling indirectly, potentially increasing vascular risk factors that are already linked to cognitive decline.
- Neuroinflammation and oxidative stress: Chronic exposure to certain additives might contribute to low-grade inflammation or oxidative processes that accelerate neural aging over time.
Importantly, the study authors emphasized that their results demonstrate association, not causation. The link between higher artificial sweetener intake and faster cognitive decline does not prove that sweeteners directly damage the brain. Residual confounding, reverse causation and measurement error (self-reported diet) are possible explanations.
Limitations and interpretation
Key limitations include reliance on self-reported dietary data that may be affected by recall error, the observational study design that cannot establish causality, and the fact that not every sweetener on the market was included. Moreover, ultra-processed foods contain many ingredients and nutritional profiles that could contribute to the observed effects, making it difficult to isolate the impact of individual sweeteners. The researchers adjusted for many covariates, but unmeasured lifestyle, socioeconomic or health factors could still influence results.
"Low- and no-calorie sweeteners are often seen as a healthy alternative to sugar," said Claudia Kimie Suemoto, MD, PhD, lead author and researcher at the University of São Paulo. "However, our findings suggest certain sweeteners may have negative effects on brain health over time. More research is needed to confirm these findings and to explore safer alternatives."
Implications for public health and choices
For clinicians and public-health practitioners, the study signals a need for balanced guidance on sugar substitutes. People with diabetes often rely on artificial sweeteners to manage blood glucose and reduce caloric intake; the current findings do not mean those individuals should abruptly stop using them without consulting healthcare providers. Rather, the study supports a cautious approach: minimize consumption of ultra-processed foods and sweetened beverages, read product labels, and consider whole-food alternatives when feasible.
Potential short-term steps for consumers include substituting flavored or diet drinks with water, unsweetened tea or coffee, and choosing fresh fruit or plain yogurt instead of sweetened packaged snacks. Natural sweeteners (e.g., honey, maple syrup) are caloric and have their own metabolic effects; their safety relative to artificial alternatives for long-term brain health remains to be rigorously tested.
Expert Insight
Dr. Ana P. Mendes, a neurologist and public-health researcher, comments: "This study is important because it is large, population-based and longitudinal, which strengthens confidence in the association. But it's not the final word. For now, the pragmatic message is moderation: reduce reliance on ultra-processed foods and beverages, pay attention to portion sizes, and consult a clinician if you rely on artificial sweeteners for diabetes management. Future randomized and mechanistic studies will be essential to determine whether specific sweeteners have direct neurobiological effects."
Conclusion
A large Brazilian cohort study links higher consumption of several common artificial sweeteners to faster declines in memory and overall thinking skills, a pattern equivalent to roughly 1.6 years of additional brain aging among the highest consumers. The association was strongest in adults under 60 and in people with diabetes. While the findings raise public-health questions about long-term use of certain low- and no-calorie sweeteners, they do not establish cause and effect. Clinicians and consumers should balance potential benefits and risks, prioritize whole foods, and await further research, including randomized trials and mechanistic studies, to clarify whether and how specific sweeteners influence brain aging.
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