Last weekend we published an article on sugar-sweetened beverages and their link to accelerated brain aging. Many readers contacted us with the logical question: "If not sugar, then artificial sweeteners are safe, right?"
A large Brazilian study published in the journal Neurology in September 2025 gives reason to re-examine this assumption. The researchers found a statistical association between high consumption of artificial sweeteners and faster cognitive decline over the years. It is important to emphasize right now: this is an observational study, showing a correlation and not causation, and the researchers themselves clarified that it does not prove the sweeteners cause harm.
The Study: 12,772 Participants, About 8 Years of Follow-up
The study was based on a cohort called ELSA-Brasil, a large Brazilian longitudinal study that recruited participants in six cities across the country starting in 2008. The analysis included 12,772 participants, with an average age of about 52, who were followed for an average of about 8 years. The analysis was led by Dr. Claudia Suemoto, an associate professor of geriatrics at the University of São Paulo.
What was actually measured:
- Dietary questionnaires from which artificial sweetener consumption was calculated.
- Cognitive tests repeated over the follow-up period, in the areas of memory, verbal fluency, and executive function.
It is important to clarify: the study measured performance on cognitive tests over time. It did not include brain imaging scans (like MRI), did not measure biomarkers, and did not examine dementia diagnoses. All it measures is the rate of decline in test scores.
The Findings
Comparing the group that consumed the highest amount of artificial sweeteners to the one that consumed the lowest amount, the study found:
- 62% faster cognitive decline in the high-consumption group.
- In practical terms, the researchers translated this to about 1.6 additional years of brain aging.
Two particularly interesting points:
- Age: The effect was especially strong in people under 60. Above age 60, no significant association was found.
- Diabetes: The association with faster cognitive decline was stronger in people with diabetes than in those without diabetes.
Which Sweeteners Were Examined?
The study examined seven low-calorie and zero-calorie sweeteners. When analyzed separately, six of them were associated with faster cognitive decline (mainly in memory and verbal fluency):
- Aspartame
- Saccharin
- Acesulfame potassium
- Erythritol
- Xylitol
- Sorbitol
The only sweetener not found to have an association with cognitive decline was Tagatose, a natural sugar found in small amounts in some fruits and dairy products.
It is important to note what was not included: the study did not examine sucralose (Splenda) or stevia, and therefore no conclusions can be drawn about them, one way or the other.
How Might This Work? Possible Mechanisms
It is important to emphasize: the study itself did not test biological mechanisms. The following mechanisms are hypotheses raised in other studies and scientific discussion, not findings of the current study.
1. Gut Microbiome Disruption (Hypothesis)
Some artificial sweeteners reach the large intestine almost intact, and there is evidence they may affect the composition of gut bacteria. Changes in the microbiome have been linked in other studies to systemic inflammation, and through the "gut-brain axis," some hypothesize a connection to brain function.
2. Paradoxical Insulin Response (Hypothesis)
Another hypothesis is that a sweet taste without calories may disrupt insulin regulation over time. Chronic insulin resistance is considered a risk factor for cognitive decline. This hypothesis connects to the finding that the association was stronger specifically in people with diabetes, but this is a cautious inference, not proof.
What to Keep in Mind from the Study
Before recommendations, it is worth clarifying the limits of what the study actually shows:
- This is an observational study. It found an association, not cause and effect. There may be confounding factors (for example, those who consume many sweeteners may differ in other habits).
- It measured performance on tests, not dementia or brain damage visible on imaging.
- The prominent association was found in the highest consumption, in those under 60, and was stronger in people with diabetes.
Approach 1: Water as Default
The simplest and safest solution. Water, mineral water, flavored water without sweeteners, unsweetened tea, herbal infusions. This is the gold standard, without the statistical risk identified by the study.
Approach 2: Reduction, Not Necessarily Complete Elimination
The association in the study was mainly found in the heaviest consumers. Reducing regular daily intake, even without giving up entirely, is a logical step based on the findings.
Approach 3: Alternatives with a Little Natural Sugar
- Unsweetened coconut water - a little natural sugar and electrolytes.
- Iced tea with lemon and a drop of honey - limited amount of sugar.
- Infused water - strawberry, cucumber, mint.
Personal Perspective
If you are a heavy consumer of diet drinks, there is no need for a dramatic detox. Sudden withdrawal from caffeine and artificial sweeteners can cause headaches, increased hunger, and irritability. Instead, gradual reduction:
- First week: Replace one drink a day with water.
- Second week: Replace two drinks a day.
- Third week and beyond: Continue to reduce regular daily intake.
- Later: Reserve the sweet drink for special occasions only.
The Summary
The Brazilian study does not prove that artificial sweeteners "destroy the brain," but it adds to the accumulating picture: choosing "diet" is not necessarily a neutral choice for the brain, at least in heavy consumers under 60 and in people with diabetes. When looking for "the next healthy drink," it is worth remembering that the oldest and most studied drink remains water.
References:
Complementary article - Sugar-sweetened beverages and the brain
Original study - Neurology 2025
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