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People often swap sugar for low-calorie sweeteners to cut calories or manage blood sugar. But new research suggests some of the most used sugar substitutes could be linked to changes in brain health over time.
Researchers from the University of Sao Paulo, Brazil, followed nearly 13,000 adults for about eight years and found that people who consumed the highest amounts of certain low- and no-calorie sweeteners experienced a faster decline in thinking and memory abilities than those who consumed the least.
The findings, published in Neurology, the medical journal of the American Academy of Neurology, do not prove that sweeteners cause cognitive decline. Instead, they show an association between higher intake and poorer cognitive outcomes over time.
“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,” study author Dr. Claudia Kimie Suemoto of the University of Sao Paulo said in a statement.
What the Researchers Studied
The study included 12,772 adults with an average age of 52. Participants completed detailed dietary questionnaires at the start of the research, allowing scientists to estimate their intake of seven commonly used sweeteners:
- Aspartame
- Saccharin
- Acesulfame K
- Erythritol
- Xylitol
- Sorbitol
- Tagatose
These sweeteners are commonly found in low-calorie products such as diet sodas, flavored waters, yogurts, desserts and energy drinks. Some are also sold as standalone sweeteners for cooking, baking, coffee and tea.
Participants were divided into three groups based on how much sweetener they consumed. The highest-intake group averaged 191 milligrams per day, while the lowest consumed an average of 20 milligrams daily.
According to the researchers, the amount of aspartame consumed by people in the highest group was roughly equivalent to the quantity found in a single can of diet soda.
Higher Intake Associated With Faster Decline
Throughout the study, participants completed assessments measuring verbal fluency, memory, word recall and processing speed.
After accounting for factors including age, sex, high blood pressure and cardiovascular disease, the researchers found that people consuming the greatest amounts of sweeteners experienced a 62 percent faster decline in overall cognitive performance than those consuming the least.
The difference was estimated to be comparable to around 1.6 years of additional aging.
People in the middle-intake group also experienced a faster decline—around 35 percent greater than those in the lowest-intake group.
The researchers found the link was particularly noticeable in adults younger than 60 and appeared stronger among people with diabetes.
Suemoto told Newsweek: “People with diabetes consumed higher quantities of sweeteners than people without diabetes, which may explain this finding partially.”
She explained that the chronic condition that prevents the body from properly processing sugar, causing it to build up in the bloodstream is related to a higher risk of cerebrovascular and neurodegenerative diseases.
She said: “The sweetener consumption could potentiate the development of these diseases, which has been shown in animal models, but to date, evidence of this finding is lacking in humans.”
However, the study found no significant association between sweetener intake and cognitive decline in participants aged 60 and older.
Which Sweeteners Were Linked to Cognitive Changes?
When the researchers analyzed the sweeteners individually, six were associated with faster declines in overall cognition, particularly memory:
- Aspartame
- Saccharin
- Acesulfame K
- Erythritol
- Sorbitol
- Xylitol
Tagatose was the only sweetener examined that was not associated with cognitive decline.
The researchers noted that people with diabetes may be especially affected by the findings because they are often encouraged to reduce sugar intake and may use sugar substitutes more frequently.
“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,” Suemoto said.
Important Limitations
The researchers stressed that the study does not show that sweeteners directly damage the brain.
Because the research was observational, it can only identify relationships between factors rather than prove cause and effect. Other lifestyle or health differences between participants could also have contributed to the results.
The study also relied on self-reported dietary information, meaning some participants may not have accurately remembered or recorded what they consumed.
In addition, the researchers only examined seven sweeteners, meaning the findings cannot be applied to every sugar substitute currently available.
Suemoto said more research is needed to confirm the findings and explore whether other alternatives to refined sugar may offer similar benefits without the same potential risks.
Update 07/21/26 03:46 a.m. ET: This story has been updated to add comments from Dr. Claudia Kimie Suemoto.
Reference
Suemoto, C.K. et al. (2026). Popular Sugar Substitutes Linked to Faster Brain Aging. ScienceDaily, https://www.sciencedaily.com/releases/2026/07/260717033213.htm.
Contact Newsweek editors on this story: Kara Dolman and James Debens
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