Popular Sugar Substitutes Linked to Faster Cognitive Decline in Long-Term Study

A long-term study of more than 12,700 Brazilian adults linked higher consumption of several low- and no-calorie sweeteners with faster declines in memory, verbal fluency, and overall thinking ability. The observational findings raise questions about common sugar substitutes but do not prove that they directly accelerate brain aging.

Editorial Note

This article provides independent health reporting and general educational information. It does not provide medical or nutritional advice, diagnose cognitive decline, or recommend that readers stop using a medically appropriate product without consulting a qualified healthcare professional.

New To Education is an independent publication. It is not affiliated with, sponsored by, endorsed by, or acting on behalf of the University of São Paulo, the American Academy of Neurology, the journal Neurology, the Brazilian Longitudinal Study of Adult Health, sweetener manufacturers, food companies, healthcare providers, or other organizations discussed in this article.

The research was observational. It identified an association between higher sweetener intake and faster cognitive decline but could not establish that the sweeteners caused the changes. The findings should also not be interpreted as evidence that replacing sugar substitutes with large amounts of ordinary sugar would improve health.

A Large Study Raises Questions About Common Sugar Substitutes

Low- and no-calorie sweeteners are commonly marketed as alternatives for people seeking to reduce sugar, manage weight, lower calorie intake, or control blood glucose.

A long-term study involving 12,772 adults in Brazil has raised new questions about whether several widely used substitutes may be associated with changes in brain health.

Researchers found that adults consuming the largest combined amounts of the sweeteners experienced faster declines in overall cognition than participants consuming the smallest amounts. The differences were particularly noticeable in memory and verbal fluency, which includes the ability to retrieve and produce words efficiently.

The association was strongest among adults younger than 60 and among participants with diabetes.

The study did not establish that sweeteners directly damaged the brain. However, its size, eight-year follow-up period, and repeated cognitive testing make the findings difficult to dismiss as a simple snapshot.

What the Researchers Studied

The research used information from the Brazilian Longitudinal Study of Adult Health, known as ELSA-Brasil.

Participants were civil servants aged 35 and older from six Brazilian cities. Their average age at the beginning of the research was approximately 52, and about 55% were women.

The study followed participants across three assessment periods between 2008 and 2019. Researchers examined dietary information collected through a food-frequency questionnaire and tracked changes in cognitive performance over an average of eight years.

Participants completed six tests examining areas such as memory, verbal fluency, working memory, word recall, processing speed, and overall thinking ability.

Researchers then compared cognitive changes with estimated consumption of seven low- and no-calorie sweeteners.

Which Sweeteners Were Examined

The researchers examined aspartame, saccharin, acesulfame potassium, erythritol, xylitol, sorbitol, and tagatose.

These substances are not all chemically identical.

Aspartame, saccharin, and acesulfame potassium are intense sweeteners that can provide sweetness in very small quantities. Erythritol, xylitol, and sorbitol are sugar alcohols frequently used in sugar-free products. Tagatose is a low-calorie sugar found naturally in small amounts in certain dairy products and fruits and can also be manufactured for food use.

The sweeteners may appear in diet beverages, flavored water, energy drinks, chewing gum, yogurt, protein products, low-calorie desserts, tabletop packets, candy, toothpaste, and medications.

Consumers may therefore use them without realizing how many different products contribute to their total intake.

Higher Intake Was Associated With Faster Cognitive Decline

Participants were divided into groups based on their estimated combined sweetener consumption.

Those in the highest-consumption group experienced a 62% faster decline in overall cognitive performance than those in the lowest group. Researchers estimated that this difference was comparable to approximately 1.6 additional years of cognitive aging during the follow-up period.

Participants in the middle-consumption group experienced a 35% faster decline, estimated as roughly 1.3 additional years of aging.

These comparisons describe differences in the rate of change measured through cognitive testing. They do not mean that every person consuming sweeteners will suddenly develop symptoms or lose exactly 1.6 years of brain function.

Population averages cannot predict what will happen to a particular individual.

The Strongest Association Appeared in Adults Under 60

One of the most surprising findings involved age.

Researchers identified associations between higher sweetener intake and faster declines in verbal fluency and overall cognition among participants younger than 60. They did not find a statistically significant association among those aged 60 or older.

This does not mean the sweeteners are necessarily safe for older adults or uniquely dangerous for younger people.

Several explanations are possible. Dietary patterns may differ across generations. Midlife exposure may influence cognition differently from later-life exposure. Older participants may also experience cognitive changes related to many competing health conditions, making the contribution of any single dietary factor harder to detect.

The researchers emphasized that dietary habits during middle age may deserve greater attention because changes affecting long-term brain health may begin years before noticeable impairment develops.

People With Diabetes May Be Especially Relevant

The association between sweetener intake and cognitive decline appeared stronger among participants with diabetes.

That finding matters because people living with diabetes may be more likely to choose low- and no-calorie sweeteners to limit sugar intake and manage blood glucose.

Diabetes itself is associated with a greater risk of cognitive impairment and dementia. Vascular disease, inflammation, insulin resistance, blood-glucose instability, and related health conditions can all affect the brain.

This creates an important problem for interpreting the results.

People with diabetes may consume more sweeteners because they already face metabolic risks connected to cognitive decline. Researchers attempted to adjust for diabetes and other health factors, but statistical adjustments cannot eliminate every difference between groups.

The study therefore cannot determine whether sweeteners increased the risk, whether underlying metabolic disease explained part of the association, or whether both contributed.

Six Sweeteners Were Associated With Cognitive Changes

When researchers examined the sweeteners separately, aspartame, saccharin, acesulfame potassium, erythritol, xylitol, and sorbitol were associated with faster declines in overall cognition.

The patterns were especially evident in memory and verbal fluency.

Tagatose was the only sweetener examined that was not associated with faster cognitive decline.

That does not establish tagatose as a proven brain-safe replacement. Its consumption may have been lower, and the evidence comes from one observational study rather than a clinical comparison designed to identify the safest option.

The findings are better interpreted as a reason for additional research than as a shopping list identifying one acceptable sweetener and six harmful ones.

The Study Did Not Prove That Sweeteners Cause Brain Aging

The headline phrase “faster brain aging” is useful for explaining the size of the observed difference, but it can be misleading when taken literally.

Researchers did not use brain scans to show that participants’ brains physically aged 1.6 years faster. They compared rates of change in cognitive test results and translated the difference into an age-equivalent estimate.

The study also did not randomly assign participants to consume particular sweeteners.

Randomized trials can more effectively establish cause and effect because researchers control the exposure and compare otherwise similar groups. This study observed existing dietary habits, which means many other factors could have influenced the results.

People consuming more sugar substitutes may differ in weight, metabolic health, medication use, diet quality, income, physical activity, sleep, cardiovascular risk, or reasons for choosing low-calorie foods.

The researchers adjusted their calculations for numerous variables, but residual confounding may remain.

Dietary Intake Was Self-Reported

Another limitation is that sweetener consumption was estimated from a food-frequency questionnaire completed at the beginning of the study.

People do not always remember accurately what they ate or drank during the previous year. They may also underestimate portion sizes or fail to recognize sweeteners hidden in processed foods.

The study did not repeatedly measure diet throughout all eight years. Participants could have changed their habits after the initial assessment.

Someone who reported drinking diet soda at the beginning may have stopped several years later. Another participant may have begun consuming more sugar-free foods during follow-up.

Repeated dietary measurements would have provided a more accurate picture of long-term exposure.

Why Might Sweeteners Affect Cognition?

The study was designed to identify an association rather than explain a biological mechanism.

Researchers have proposed several possibilities that future studies may examine.

Some sweeteners may alter the gut microbiome, which includes the bacteria and other microorganisms living in the digestive system. Changes in the microbiome may influence metabolism, inflammation, immune function, and signaling between the gut and brain.

Other possible pathways include glucose intolerance, oxidative stress, changes in insulin signaling, vascular effects, and neuroinflammation.

Different sweeteners may also behave differently inside the body. It would be overly simplistic to assume that aspartame, erythritol, sorbitol, and xylitol all affect cognition through the same process merely because consumers use them as sugar substitutes.

The proposed mechanisms remain uncertain and should not be presented as established explanations for the study’s results.

Replacing Sweeteners With Sugar Is Not a Simple Solution

The findings do not mean ordinary sugar is harmless.

High intake of added sugar can contribute to weight gain, tooth decay, diabetes, metabolic disease, and cardiovascular risk. Those conditions may themselves affect long-term brain health.

Replacing every diet drink with a heavily sweetened beverage could trade one uncertain risk for several well-established ones.

The more useful question may be whether people can gradually reduce their preference for intense sweetness overall.

Water, unsweetened tea, plain coffee, sparkling water without added sweeteners, whole fruit, and minimally processed foods may help reduce dependence on both added sugar and sugar substitutes.

Dietary changes should remain practical, especially for people who use sweeteners as part of diabetes management or another medically supervised plan.

Not Every “Natural” Alternative Is Automatically Healthier

Health stories about artificial sweeteners often prompt recommendations for honey, maple syrup, coconut sugar, agave, fruit syrup, or other products marketed as natural.

These ingredients may differ in flavor, processing, and small amounts of nutrients, but they still contribute sugar and calories.

“Natural” does not automatically mean safe in unlimited quantities, and “artificial” does not automatically mean toxic.

Stevia and monk-fruit extracts were not among the seven sweeteners evaluated in this study, so the results cannot be used to determine how those products affect cognition.

Likewise, the absence of an association for tagatose in this analysis does not prove that it improves brain health.

Consumers should be cautious when companies use one study to market another sweetener as a guaranteed healthy alternative.

Food Labels Can Make Sweetener Intake Difficult to Track

Sweeteners can appear under several names and may be combined within one product.

A beverage could contain acesulfame potassium and aspartame. A protein bar might include erythritol, xylitol, or sorbitol. A product labeled “no added sugar” may still contain low-calorie sweeteners.

Sugar alcohols may also be listed within the carbohydrate section of a nutrition label rather than presented prominently on the front of the package.

People interested in reducing their intake may need to read ingredient lists rather than relying only on claims such as “diet,” “keto,” “low carb,” “light,” or “sugar free.”

Frequent use across several foods can add up even when each serving contains a modest quantity.

What Consumers Can Reasonably Do Now

The study does not justify panic or an abrupt dietary change based on one headline.

A reasonable response is to examine how frequently sweetened products appear in the diet and whether they are replacing water or minimally processed foods.

Someone who occasionally chews sugar-free gum is not necessarily in the same situation as someone consuming several diet beverages, protein products, desserts, and tabletop sweeteners every day.

Gradual reduction may be easier than immediate elimination. People can dilute sweetened drinks, alternate them with water, choose unsweetened products, reduce the number of sweetener packets used, or allow their taste preferences to adjust over time.

Individuals with diabetes, eating disorders, metabolic conditions, or medication-related dietary needs should discuss major changes with a qualified healthcare professional.

Cognitive Health Depends on Much More Than One Ingredient

Brain health develops through the interaction of many factors.

Blood pressure, diabetes management, physical activity, sleep, smoking, alcohol use, social connection, hearing, depression, education, diet quality, and cardiovascular health may all influence cognitive aging.

Focusing entirely on one sweetener could distract from interventions supported by stronger evidence.

Regular exercise, adequate sleep, management of high blood pressure, avoiding tobacco, maintaining social engagement, and eating a balanced diet remain important parts of long-term health.

The sweetener study adds another possible factor to investigate. It does not replace the broader foundations of healthy aging.

Why the Study Still Matters

Observational research cannot prove causation, but it can identify patterns worthy of closer examination.

Low- and no-calorie sweeteners are consumed widely, including by children, middle-aged adults, people with diabetes, and individuals trying to manage weight.

Even a modest effect could matter at a population level if exposure is widespread and continues for many years.

The findings also challenge the assumption that sugar substitutes are biologically inactive simply because they provide few or no calories.

Food additives may affect the body through pathways unrelated to calorie content.

The next steps should include studies with repeated dietary measurements, randomized interventions where practical, brain imaging, biological markers, and closer comparisons among individual sweeteners.

Key Takeaways

A long-term observational study followed 12,772 Brazilian adults for an average of eight years and examined consumption of seven low- and no-calorie sweeteners.

Participants consuming the highest combined amounts experienced a 62% faster decline in overall cognitive test performance than those consuming the lowest amounts. Researchers described the difference as comparable to approximately 1.6 additional years of cognitive aging.

The strongest associations appeared among adults younger than 60 and people with diabetes.

Aspartame, saccharin, acesulfame potassium, erythritol, xylitol, and sorbitol were individually associated with faster cognitive decline. Tagatose was not associated with decline in this study.

The research was observational and relied partly on self-reported dietary information. It did not prove that sweeteners caused cognitive decline or physical aging of the brain.

The original research was published in 2025 and received renewed public attention in July 2026.

Frequently Asked Questions

Did This Study Prove That Artificial Sweeteners Cause Dementia?

No. The study identified an association with changes in cognitive testing. It did not determine that sweeteners caused dementia or diagnose participants with dementia based on their intake.

How Many People Participated?

The analysis included 12,772 Brazilian adults with an average baseline age of approximately 52.

How Long Were Participants Followed?

Participants were followed for an average of eight years across three assessment periods.

Which Sweeteners Were Associated With Faster Decline?

Aspartame, saccharin, acesulfame potassium, erythritol, xylitol, and sorbitol were associated with faster decline in overall cognition, particularly memory and verbal fluency.

Was Stevia Included?

No. Stevia was not among the seven sweeteners examined, so the study cannot determine whether it has the same association.

Was Monk Fruit Included?

No. Monk-fruit sweetener was not evaluated.

Should People Replace Diet Drinks With Sugary Drinks?

The study does not support increasing ordinary sugar intake. High added-sugar consumption has its own established health risks. Reducing overall dependence on intensely sweetened products may be a more balanced approach.

Why Was the Association Stronger in People With Diabetes?

People with diabetes may consume more sugar substitutes and already face metabolic and vascular risks connected to cognitive health. The study could not fully determine why the association was stronger.

Did Researchers Examine Participants’ Brains?

The primary findings came from repeated cognitive tests and dietary assessments rather than proof of physical brain aging through medical imaging.

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Final Thoughts

Sugar substitutes have often been presented as a straightforward solution to the health problems associated with added sugar.

The new research suggests the picture may be more complicated.

Adults who consumed the highest amounts of several low- and no-calorie sweeteners experienced faster declines in memory, verbal fluency, and overall cognitive performance during eight years of observation. The association appeared particularly strong among adults under 60 and people living with diabetes.

Those findings deserve attention, but they do not justify claiming that an occasional diet beverage causes brain damage or dementia.

The researchers did not randomly assign sweeteners, repeatedly measure every dietary change, or prove a biological mechanism. Participants with higher intake may have differed from other groups in ways the study could not completely measure.

The responsible conclusion sits between dismissal and alarm.

Sugar substitutes should not automatically be treated as metabolically or neurologically neutral merely because they contain few calories. At the same time, one observational study cannot establish that each sweetener directly harms human cognition.

Consumers may benefit from examining how often heavily sweetened products appear in their diets and reducing unnecessary exposure when practical. That does not require replacing them with large quantities of sugar or chasing another fashionable substitute advertised as completely safe.

The larger lesson concerns dietary patterns rather than a single packet or ingredient.

Brain health is supported over time through movement, sleep, cardiovascular care, social connection, management of diabetes and blood pressure, and a balanced diet centered on minimally processed foods.

The sweetener findings add a meaningful warning sign to that larger picture.

They are not the final verdict.