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A major study published September 3, 2025, in Neurology® has revealed that adults who regularly consume high amounts of artificial sweeteners—often found in diet sodas and ultra-processed foods—may experience significantly faster declines in memory and thinking skills, particularly those under 60 and people with diabetes. While the research does not prove causation, it raises new questions about the safety of long-term sugar substitute use and its impact on brain health.
Key Findings
Researchers from the University of São Paulo tracked 12,772 Brazilian adults, average age 52, for eight years, assessing cognitive skills and dietary habits through questionnaires and regular testing. Participants were grouped by sweetener consumption:
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Lowest intake: ~20 mg/day (about a teaspoon per week)
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Highest intake: ~191 mg/day (roughly one can of diet soda daily)
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Sorbitol saw the highest individual intake, averaging 64 mg/day.
Those in the highest consumption group experienced a 62% faster decline in overall cognitive abilities and memory—equivalent to an extra 1.6 years of brain aging—compared to the lowest group. Even moderate consumption was linked to a 35% faster decline, or 1.3 extra years of cognitive aging. The association was strongest for people under age 60 and those living with diabetes, for whom sweeteners are commonly recommended.
Expert Perspectives
Lead author Dr. Claudia Kimie Suemoto, an associate professor of geriatrics at the University of São Paulo, commented:
“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”.
Dr. Vivek Mishra, a neurologist at Apollo Hospitals (not involved in the study), noted,
“While causation cannot be established from this study alone, it points to a growing body of evidence that urges careful use and further research. The results are particularly significant for younger adults and those managing diabetes, who may rely more heavily on artificial sweeteners.”
Context and Background
Artificial sweeteners, also called low- and no-calorie sweeteners (LNCS), are common in diet drinks, yogurt, and sugar-free foods. They include the compounds aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose.
Previously, studies have associated these sweeteners with risks of type 2 diabetes, cardiovascular disease, and depression, but few have investigated long-term cognition. This research is the largest and longest prospective study to date, highlighting a potential public health concern given global sweetener consumption trends.
Some experimental evidence suggests LNCS and sugar alcohols could promote oxidative stress, neuroinflammation, and disruptions in the gut-brain axis, potentially impairing cognitive function over time.
Implications for Public Health
The findings signal a need for caution, especially in younger adults and those with metabolic conditions.
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People under 60 and those with diabetes who consumed the most sweeteners showed the swiftest declines in memory and cognition.
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Experts advise that, whenever possible, consumers limit both sugary and high-sweetener processed foods and opt for a balanced diet rich in whole, minimally processed foods.
While non-sugar alternatives can help manage blood sugar or caloric intake, individuals should consider potential long-term brain health effects when choosing between sugar and its substitutes.
Limitations and Counterarguments
The study authors caution that the research is observational and cannot prove that sweeteners cause cognitive decline—only that there is a strong association.
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Dietary data were self-reported, which can introduce recall bias.
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Not every available artificial sweetener was studied, and the effects of certain alternatives (such as tagatose) appeared neutral or unstudied.
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Unmeasured confounding factors (such as other dietary habits, exercise, or health status) could contribute to the findings.
Further research is required to:
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Replicate these results in other populations.
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Better isolate specific sweeteners or combinations most responsible for cognitive effects.
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Explore whether natural sugar alternatives (e.g., honey, maple syrup) are safer substitutes.
Practical Takeaways
For health-conscious readers and those with diabetes:
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Regular, sizable consumption of artificial sweeteners—as little as one can of diet soda per day—may be linked to faster brain aging.
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Occasional use is less clear, but moderation appears prudent until more evidence emerges.
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Emphasize whole foods and use a variety of sweetening options, while consulting healthcare providers for individualized guidance.
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Long-term impacts may be more pronounced starting in midlife, a crucial period for brain health.
Medical Disclaimer:
This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.
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