Could Your Sugar Substitute Come With a Cognitive Trade-Off?
Key takeaways
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In a study of 12,772 adults followed for approximately eight years, higher consumption of certain sugar substitutes was associated with faster declines in memory and thinking.
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The highest-intake group experienced a 62% faster rate of decline than the lowest-intake group. That does not mean participants lost 62% of their cognitive ability.
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Six of seven sweeteners studied showed an association. The pattern was evident among adults younger than 60, but not among older participants.
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The study was observational and relied on self-reported diet. It cannot establish that sweeteners caused the differences.
A sugar swap with an unanswered question
Replacing sugar changes a food’s calorie content. Whether it changes the long-term trajectory of brain health is a different question.
Researchers examined that possibility in a Brazilian study whose participants were 52 years old, on average, at enrollment. They estimated sweetener intake using dietary questionnaires and assessed memory, language, and processing speed at three points over approximately eight years.
Participants consuming the most sweeteners showed faster declines in overall cognitive performance—even after researchers accounted for several differences in health and lifestyle.
The finding is worth investigating. It is not proof that a diet drink damages the brain.
What “62% faster” actually means
The highest-intake group consumed an estimated 191 milligrams of the studied sweeteners daily, compared with 20 milligrams in the lowest-intake group.
Their rate of cognitive decline was 62% faster. Researchers described that difference as equivalent to approximately 1.6 additional years of cognitive aging over the study period.
The important distinction is rate. This was a difference in how test scores changed—not a 62% loss of memory, a brain scan showing accelerated aging, or a prediction of what will happen to an individual.
The middle-intake group also showed faster decline, although the difference was smaller.
Not every sweetener showed the same pattern
Six sweeteners were associated with faster cognitive decline:
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Aspartame
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Saccharin
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Acesulfame-K
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Erythritol
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Sorbitol
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Xylitol
Tagatose, the seventh sweetener examined, did not show an association. That does not establish it as protective or prove it is a better replacement.
The study also did not evaluate every available sugar substitute, so its findings should not be extended to ingredients that were not studied.
Why the association needs unpacking
People do not choose sweeteners at random.
Someone may switch to low-sugar products because of changes in weight, blood-sugar regulation, or other health concerns. Those underlying differences could also influence cognitive performance.
Sweeteners may also travel with a broader dietary pattern. Their presence in packaged drinks, desserts, and other products makes it difficult to separate the ingredient from the foods and habits surrounding it.
Statistical adjustments help, but they cannot eliminate every alternative explanation. Dietary recall adds another limitation: estimated intake may not accurately reflect what participants consumed or how their habits changed.
The takeaway
This study raises a meaningful question about frequent sugar-substitute consumption and long-term cognitive health. It does not answer whether the sweeteners themselves drive the association.
The next step is research that can better distinguish the ingredients’ effects from the health conditions, food choices, and habits that influence who uses them.
References:
- Natalia Gomes Gonçalves, Euridice Martinez-Steele, Paulo A. Lotufo, Isabela Bensenor, Alessandra C. Goulart, Sandhi Maria Barreto, Luana Giatti, Carolina Perim de Faria, Maria del Carmen Bisi Molina, Paulo Caramelli, Dirce Maria Marchioni, Claudia Kimie Suemoto. Association Between Consumption of Low- and No-Calorie Artificial Sweeteners and Cognitive Decline. Neurology, 2025; 105 (7) DOI: 10.1212/WNL.0000000000214023
- Thomas Monroe Holland. The Dark Side of Sweet. Neurology, 2025; 105 (7) DOI: 10.1212/WNL.0000000000214129