Study finds higher intake of common sugar substitutes linked to faster cognitive decline

A prospective study of nearly 13,000 Brazilian adults found that higher consumption of several widely used low- and no-calorie sweeteners was associated with faster declines in cognitive function over an average of eight years, according to research published in Neurology, the journal of the American Academy of Neurology (aan.com).

The analysis drew on data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Participants had a mean age of about 52 at baseline. Researchers assessed intake of seven sweeteners—aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose—via food frequency questionnaires and divided people into tertiles of total consumption. The lowest tertile averaged roughly 20 mg per day; the highest averaged about 191 mg per day (for aspartame, roughly the amount in one can of diet soda). Cognitive testing covering verbal fluency, working memory, word recall, and processing speed occurred at baseline, midpoint, and end of follow-up (neurology.org).

After adjustment for age, sex, blood pressure, cardiovascular disease, and other factors, those in the highest tertile of combined sweetener intake showed a 62% faster rate of decline in global cognition compared with the lowest tertile—equivalent to approximately 1.6 additional years of aging. The middle tertile showed a 35% faster decline, or about 1.3 years. Associations were clearer among participants younger than 60 and stronger in those with diabetes. No significant link appeared in those aged 60 and older (sciencedaily.com; aan.com).

When sweeteners were examined individually, aspartame, saccharin, acesulfame-K, erythritol, sorbitol, and xylitol were each linked to faster global cognitive decline, particularly affecting memory and verbal fluency domains. Tagatose showed no association. Lead author Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo, noted that while low- and no-calorie sweeteners are often viewed as healthier alternatives to sugar, the results raise the possibility of longer-term effects on brain health, especially for middle-aged adults and people with diabetes who may use them more frequently (aan.com).

The study is observational and cannot establish that the sweeteners cause cognitive decline. Limitations include reliance on self-reported diet (subject to recall error), incomplete coverage of all available sweeteners, potential residual confounding, and attrition. Dietary data were collected primarily at baseline. An accompanying editorial highlighted the findings’ relevance for clinical dietary advice, particularly in patients with metabolic or cerebrovascular risk factors, while calling for further research (cnn.com).

Industry representatives have pointed to existing safety assessments by regulatory authorities affirming that approved low- and no-calorie sweeteners are safe when used within established limits. The authors themselves called for additional studies to confirm the associations and to evaluate possible alternatives such as certain natural sweeteners.

These results add to a growing body of observational research examining non-nutritive sweeteners and long-term health outcomes, including prior work on cardiovascular and metabolic endpoints. The sweeteners studied appear frequently in ultra-processed products marketed as low-calorie or sugar-free, including diet beverages, yogurts, and desserts.

Why this is uncovered

The findings received coverage in specialty medical outlets, ScienceDaily, health-focused sites, and some national media such as CNN around the September 2025 publication, along with later specialist summaries. Broader pickup in major general newspapers and wire services remained limited relative to the widespread consumer use of these products.