There’s no way to sugarcoat it: Artificial sweeteners may harm brain health, according to a recent study from the American Academy of Neurology (AAN).
After following nearly 13,000 adults in Brazil over eight years, researchers found that people who consumed the most sugar substitutes experienced faster cognitive declines than those who consumed the least. The results were published in the fall of 2025 in Neurology, the medical journal of the AAN.
Lead author Natalia Gomes Gonçalves, PhD, a professor in the Department of Preventive Medicine at the University of São Paulo Medical School, and coauthors sought to expand on previous research that linked artificially sweetened food and beverages with dementia.
“Since many ultraprocessed foods are artificially sweetened with low- and no-calorie sweeteners (LNCS), we asked ourselves if high consumption of LNCS could be associated with accelerated cognitive decline as well,” she says.
The researchers looked at these seven artificial sweeteners and additives commonly found in highly processed foods:
- aspartame (typically sold as NutraSweet and Equal)
- saccharin (Sweet’N Low)
- acesulfame-K (Sunett and Sweet One)
- erythritol (used in Splenda coffee creamers and Truvia)
- xylitol, sorbitol, and tagatose (additives)
After completing questionnaires related to their diet, participants took cognitive tests that tracked their memory, language, and processing skills over time. “We expected to see some degree of accelerated cognitive decline,” Gonçalves says.
Researchers found that the overall thinking and memory skills of participants who consumed the most sweeteners declined 62 percent faster than those who consumed the least — the equivalent of 1.62 years of aging. Those who consumed a moderate amount experienced a cognitive decline as well, equivalent to about 1.3 years of aging.
The effect was even stronger in people with diabetes who may rely on sugar substitutes to add sweetness without raising blood-sugar levels.
Researchers also found that people under 60 who consumed the most sweeteners experienced faster rates of verbal and cognitive decline than those who consumed the least. There was no such link among people over 60.
Notably, this is just one study, and it shows correlation, not cause. To prove cause, says Gonçalves, the researchers would have to compare cognitive decline among people who did and did not consume artificial sweeteners.
The study had limitations as well: Participants self-reported their diets, which isn’t always reliable, and the study did not evaluate all sugar substitutes. The team also did not explore the mechanisms by which artificial sweeteners may affect the brain. Previous research has shown that when aspartame is digested, it can raise levels of compounds that inhibit the brain’s function and make it more vulnerable to oxidative stress, both of which can impede cognition.
While there’s no need to panic over the results, Gonçalves says, it’s worthwhile to consider your use of artificial sweeteners. She recommends swapping them for natural alternatives — applesauce, honey, maple syrup, or coconut sugar — whenever possible.
“LNCS are a tempting option,” she admits. “But they may have risks we don’t fully understand.”
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