Artificial sweeteners commonly found in diet sodas and sugar-free energy drinks may not be as harmless as widely perceived, particularly when it comes to brain health.
A study published in the journal Neurology found that artificial sweeteners may be associated with faster cognitive decline, suggesting that heavy consumption could contribute to brain aging by as much as 1.6 years.
The research tracked 12,772 adults in Brazil over an eight-year period. Participants had an average age of 52 at the start of the study and were asked to complete questionnaires identifying which of seven sweeteners they consumed most: aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose.
These sweeteners are commonly found in products such as sugar-free gum, candy, energy drinks, low-calorie yogurt, and flavored water. Some are also sold separately as sugar substitutes for baking or as sweeteners for coffee.
Among the seven, sorbitol was the most consumed, with an average intake of 64 milligrams per day. Overall, high consumers of artificial sweeteners averaged 191 milligrams daily—roughly equivalent to the amount found in a can of diet soda.
To assess cognitive performance, participants underwent tests at the beginning, midpoint, and end of the study, measuring working memory, word recall, verbal fluency, and processing speed.
After eight years, researchers found that participants with the highest intake of artificial sweeteners experienced a 62% faster rate of cognitive decline compared to those who consumed less. Six of the seven sweeteners were linked to cognitive decline, except for tagatose, which showed a negative association.
The study also found that the effects varied by age group. Participants aged 60 and above showed no significant cognitive changes, while younger and middle-aged adults experienced more pronounced declines, particularly in verbal fluency and overall cognitive function.
“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,” said Claudia Kimi Suemoto of the University of Sao Paulo, who led the study.
However, Suemoto cautioned that the findings do not establish causation.
“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,” she said.
“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,” she added.
Supporting evidence from animal studies suggests that some sweeteners, such as aspartame, may trigger inflammatory responses in brain tissue. Sugar alcohols like erythritol and sorbitol have also been linked to changes in the gut microbiome and potential disruption of the blood-brain barrier.
Some neurologists have also suggested that artificial sweeteners may interfere with the brain’s natural sugar reward system, potentially affecting the ability to perform complex tasks.
In an accompanying editorial, Thomas Holland of Rush University advised moderation to protect long-term brain health.
Holland recommended avoiding sugar substitutes as a daily staple, suggesting alternatives such as replacing diet sodas with sparkling water and opting for fresh fruits instead of artificially sweetened products. — Photo from Cleveland Clinic
