For years, artificial sweeteners have been marketed and widely accepted as the “smart” alternative to sugar — a way to enjoy sweetness without the calories, blood sugar spikes, or dental damage associated with regular sugar consumption. A large new study published in Neurology, the medical journal of the American Academy of Neurology, is raising a genuinely important question about whether that reputation is fully deserved.
The research found that adults consuming the highest amounts of several common sugar substitutes experienced substantially faster decline in memory and thinking skills over time compared to those consuming the least.
A Large, Long-Term Study
The study followed 12,772 adults living across Brazil, with an average age of 52 at the start. Researchers tracked participants for approximately eight years, making this one of the longer-running investigations into the relationship between artificial sweetener consumption and cognitive health.
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At the beginning of the study, participants completed detailed food questionnaires describing everything they had eaten and drunk over the previous year. Based on this data, researchers calculated each person’s total intake of seven common sweeteners: aspartame, saccharin, acesulfame K, erythritol, xylitol, sorbitol, and tagatose.
These ingredients show up constantly in modern diets — in flavored water, diet soft drinks, energy drinks, low-calorie yogurt, and desserts marketed as “sugar-free” or “diet.” Several are also sold individually for use in coffee, tea, cooking, and baking.
Participants were divided into three groups based on total sweetener intake: those consuming the least (averaging 20 mg/day), a middle group, and those consuming the most (averaging 191 mg/day). For context, the highest-intake group’s aspartame consumption was roughly equivalent to what’s found in one can of diet soda. Sorbitol was the most heavily consumed individual sweetener overall, averaging 64 mg/day.
Cognitive testing was conducted at the beginning, midpoint, and end of the eight-year study, measuring several distinct aspects of brain function: verbal fluency (quickly retrieving and producing words), working memory (the brain’s short-term system for holding and using information), word recall, and processing speed.
The Core Finding: Faster Decline With Higher Intake
After adjusting for age, sex, high blood pressure, cardiovascular disease, and other relevant health factors, a clear pattern emerged.
People in the highest sweetener consumption group experienced a 62% faster decline in overall thinking and memory abilities compared to those in the lowest group. Researchers calculated that this difference was equivalent to approximately 1.6 additional years of cognitive aging.
Even the middle consumption group showed a meaningfully faster decline — 35% faster than the lowest group, equivalent to roughly 1.3 additional years of aging.
This is a dose-response pattern — meaning the effect scaled up progressively with increased consumption, rather than appearing only at extreme intake levels. Dose-response relationships are generally considered a stronger form of evidence in observational research than a simple yes/no association.
Who Was Most Affected
Two specific groups showed a particularly strong association between sweetener intake and cognitive decline.
Adults under 60: Among younger participants, those who consumed the most sweeteners showed faster declines specifically in verbal fluency and overall cognitive performance compared to those who consumed the least. Notably, researchers did not find the same association among participants over 60 — an unexpected pattern that adds nuance to how these findings should be interpreted.
People with diabetes: The connection between sweetener intake and faster cognitive decline was stronger among people with diabetes than among those without the condition. This may partly reflect how sweeteners are actually used in the real world — people with diabetes are frequently advised to limit foods that rapidly raise blood sugar, making them more likely to rely heavily on sugar substitutes as a daily dietary strategy.
Which Specific Sweeteners Were Linked To Decline
When researchers examined each sweetener individually, six of the seven showed an association with faster cognitive decline, particularly affecting memory:
- Aspartame
- Saccharin
- Acesulfame K
- Erythritol
- Sorbitol
- Xylitol
Tagatose was the only sweetener in the study not linked to cognitive decline — an interesting distinction that may be worth further investigation, since tagatose has a different metabolic profile than several of the other sweeteners studied.
What The Lead Researcher Said
“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,” said study author Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo in Brazil.
Suemoto also pointed toward important next steps for research: “While we found links to cognitive decline for middle-aged people both with and without diabetes, people with diabetes are more likely to use artificial sweeteners as sugar substitutes. More research is needed to confirm our findings and to investigate if other refined sugar alternatives, such as applesauce, honey, maple syrup or coconut sugar, may be effective alternatives.”
Important Limitations To Understand
This study has several limitations that are essential to keep in mind before drawing firm conclusions.
It was observational, not experimental. The study identified an association between higher sweetener intake and faster cognitive decline — it did not establish that sweeteners directly cause cognitive decline. Other factors not fully captured by the researchers’ adjustments could help explain the pattern observed.
Self-reported diet data has known limitations. Participants reported their own food and drink intake from memory, and people commonly forget items or misjudge quantities when completing dietary questionnaires — introducing potential inaccuracy into the sweetener intake estimates.
Not every sweetener was studied. The seven sweeteners examined don’t represent every artificial or low-calorie sweetener currently used in food and beverages, so these findings cannot be generalized to all sugar substitutes, including some newer or less common formulations not included in this research.
What This Means For Your Diet Right Now
Given that this is observational research rather than proof of direct causation, the most reasonable response is moderation and awareness rather than panic.
If you regularly consume diet sodas, flavored waters, or “sugar-free” processed foods containing these specific sweeteners — particularly aspartame, saccharin, acesulfame K, erythritol, sorbitol, or xylitol — this research is a reasonable prompt to:
- Read ingredient labels to understand which sweeteners you’re actually consuming and how often
- Consider moderating heavily processed “diet” or “sugar-free” products rather than eliminating them entirely based on one study
- Prioritize whole foods and naturally sweet options like fruit where practical
- Discuss sweetener use with your doctor, particularly if you have diabetes and rely on these products regularly
Key Takeaways
- A study of 12,772 adults followed for 8 years found high sweetener intake linked to 62% faster cognitive decline, equivalent to 1.6 additional years of brain aging
- Six sweeteners — aspartame, saccharin, acesulfame K, erythritol, sorbitol, and xylitol — were individually linked to faster decline; tagatose was not
- The association was strongest in adults under 60 and in people with diabetes
- This is an observational study; it shows a link, not proof that sweeteners directly cause cognitive decline
- More research is needed, including investigation into whether other sugar alternatives carry similar or different risks
When To See A Healthcare Professional
If you have concerns about memory changes, cognitive decline, or how your diet — including sweetener use — may be affecting your health, especially if you have diabetes, speak with your doctor or a registered dietitian. They can help you make personalized, evidence-based dietary decisions.
⚠️ Medical Disclaimer: This article is for informational purposes only and is based on observational research that shows an association, not proof of causation. It does not constitute medical advice. Always consult a qualified healthcare professional before making significant changes to your diet.
Source: American Academy of Neurology / Neurology — July 18, 2026
Journal Reference: Claudia Kimie Suemoto et al. Published in Neurology, 2026.
