SÃO PAULO — People who consumed the most low- and no-calorie sweeteners showed faster declines in memory and thinking over about eight years than people who consumed the least, according to a large Brazilian study published in Neurology, the medical journal of the American Academy of Neurology (AAN). The study does not prove that sweeteners cause memory decline, and its authors say more research is needed.
The study, led by Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo, followed 12,772 adults in Brazil whose average age was 52 at the start. Participants reported their diets and took tests of memory, language and thinking.
Illustration: Diet soda cans and sugar substitute packets beside a stylised brain, representing the study of low- and no-calorie sweeteners and memory decline.
What Happened
The study examined seven low- and no-calorie sweeteners: aspartame, saccharin, acesulfame-K, erythritol, sorbitol, xylitol and tagatose. Six of the seven — all except tagatose — were linked to faster decline in thinking and memory. The paper was first published in 2025, in Neurology 2025;105(7), DOI 10.1212/WNL.0000000000214023, and the journal corrected and replaced it in July 2026 after the authors audited and reran their analysis. The American Academy of Neurology updated its release in late October 2026, and news coverage followed between 29 October and 3 November 2026, including in Men's Journal, ScienceDaily and Fox News Digital.
The highest-consumption group showed a 62 percent faster decline in overall thinking and memory than the lowest group, according to the journal figure. The AAN release described the difference as 63 percent in one version of its announcement; this article uses the 62 percent journal figure. Researchers estimated the difference as about 1.6 extra years of cognitive ageing over the study period — a way of expressing how much faster, on average, the highest group's scores moved, not a literal loss of 1.6 years of memory for any individual. The middle group showed a 35 percent faster decline than the lowest group.
The consumption gap was large: the highest group averaged 191 milligrams of sweeteners a day, against 20 milligrams a day in the lowest group. The study did not identify a safe or unsafe amount. The association was stronger in people under 60, and no link was found in older participants. It was also stronger among people with diabetes, for whom low- and no-calorie sweeteners are often recommended to reduce sugar intake.
The study did not compare sweeteners with sugar. It compared people who consumed more sweeteners with people who consumed fewer, so it cannot answer whether sweeteners are better or worse for thinking and memory than sugar itself.
Background
Low- and no-calorie sweeteners give food and drink a sweet taste without the calories of sugar. They appear in diet drinks, tabletop sweetener packets, and packaged foods and drinks described as sugar-free or low in sugar. For many people they are routine: a packet in coffee or tea, a diet drink with a meal, or a product chosen because it says sugar-free on the label.
Aspartame, saccharin and acesulfame-K are long-established artificial sweeteners. Erythritol, sorbitol and xylitol are sugar alcohols, sweeteners that occur in some foods and are also made for use in food and drink. Tagatose, the one sweetener not linked to faster decline, is less widely used. The study looked at the seven together and individually, and the pattern was consistent across six of them.
Illustration: Sugar-free products and sweetener packets on a grocery shelf, showing how low- and no-calorie sweeteners appear in everyday shopping.
The participants were part of a long-running study of adult health in Brazil. Memory, language and thinking were tested more than once, so researchers were looking at how scores changed over time, not at a single snapshot. Diet, however, was reported by participants themselves, and only at the start of the study. If a person's diet changed during the eight years that followed, that change would not have been captured in the same way. That is one reason the authors describe their findings as an association needing confirmation, rather than proof of a cause.
Lead author Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo, has framed the findings carefully. According to the study's reporting, she said that "certain sweeteners may have negative effects on brain health over time" and that "More research is needed to confirm our findings." Suemoto also suggested that future research explore other sugar substitutes, including applesauce, honey, maple syrup and coconut sugar. That is a direction for further study, not a recommendation to readers: the study did not test those alternatives.
Illustration: An older adult doing a memory test with a doctor, with stylised brain imagery, representing the cognitive testing used in the study.
Why It Matters
The study matters first because of who uses these products. They are in drinks and foods many people consume daily, often because they are trying to make a healthier choice — watching their weight, or managing blood sugar. A study linking the highest consumption to faster change in memory and thinking therefore touches a widespread, routine habit, often made with good intentions.
It also matters because of the scale reported: a 62 percent faster decline, and about 1.6 extra years of cognitive ageing over the study period, describe a group average over about eight years, not a prediction for any one person. They are large enough to justify the attention the study has received, and the further research its author has called for. If an association of that size were confirmed by other studies, it would have real implications for how sweeteners are discussed and used. If it were not confirmed, it would still have prompted the checks needed before any change in advice.
For people with diabetes, where the association was stronger, the finding creates a tension that one paper cannot resolve. Low- and no-calorie sweeteners are recommended by the American Diabetes Association and other experts for people with diabetes, according to the industry response to the study, because reducing sugar intake is central to managing blood sugar. Research looking specifically at people with diabetes, over a long period, with diet measured more than once, would be needed before anyone could say whether the association holds up, and how it should be weighed against the known reasons for limiting sugar.
Industry groups have stressed that the study does not show causation. The Calorie Control Council, which represents makers of low- and no-calorie sweeteners, and sweetener makers more broadly, note that there is no causal evidence linking these products to memory decline. That response does not dismiss the study; it places it in the category to which the study itself belongs — observational research reporting an association, not an experiment proving a cause.
The study also matters because of what it does not claim. It does not say sweeteners cause dementia, or that everyone who uses them will experience faster memory decline. It does not identify a threshold, and it does not compare sweeteners with sugar. A finding that is overstated is harder to test and harder for readers to use. The most useful response is not alarm, and not dismissal, but a clear account of what was found, how it was found, and what would be needed to know more. The age pattern also invites questions: the association was stronger under 60, with no link in older participants, and a single study cannot settle why.
What Happens Next
What happens next is, first, more research. Confirmation would mean other studies, in other groups of people, with diet measured repeatedly and memory, language and thinking tested over time, looking closely at the questions this study raises: whether the pattern holds for people under 60 and for people with diabetes, and whether different sweeteners behave differently over a long period. Future research could also take up Suemoto's suggestion to explore applesauce, honey, maple syrup and coconut sugar — as a direction for researchers, not as advice for readers to switch now.
For now, existing guidance has not changed. Low- and no-calorie sweeteners continue to be recommended by the American Diabetes Association and other experts for people with diabetes, according to the industry response reported in coverage of the study, and the study itself does not recommend stopping their use. Anyone concerned about their own consumption, or who has diabetes or another condition affecting how they manage sugar, should discuss it with a doctor or another qualified health professional. A news article, however carefully reported, is not a substitute for that conversation.
The study will continue to be discussed in the wider conversation about diet and brain health. The Brazilian study has added a large, long-running piece of evidence to that conversation, with a clear result, clear limits, and a clear call for more work. Whether that result is confirmed, qualified or overturned will depend on what the next studies find.
Readers following the story should expect the next developments to come from further studies rather than from this paper alone. The corrected July 2026 version of the paper is the version now in the journal, and the AAN's updated late-October 2026 release is the current account of the findings. Any change in guidance would follow confirmation by other research, not a single study, however large.
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FAQ
What did the Brazilian study find about sweeteners and memory?
People who consumed the most low- and no-calorie sweeteners showed a 62 percent faster decline in overall thinking and memory than people who consumed the least, over about eight years in a study of 12,772 adults in Brazil. The middle group showed a 35 percent faster decline, and the difference for the highest group was estimated as about 1.6 extra years of cognitive ageing.
Which sweeteners were examined in the study?
Seven: aspartame, saccharin, acesulfame-K, erythritol, sorbitol, xylitol and tagatose. Six — all except tagatose — were linked to faster decline. The study was led by Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo, and published in Neurology, the medical journal of the American Academy of Neurology.
Does the study prove that sweeteners cause memory decline?
No. It was observational research, based on self-reported diet at baseline only, and it cannot prove causation. Its author said certain sweeteners may have negative effects on brain health over time and that more research is needed to confirm the findings. The Calorie Control Council has also noted there is no causal evidence.
Was the link the same for everyone in the study?
No. The association was stronger in people under 60, and no link was found in older participants. It was also stronger among people with diabetes. The highest group averaged 191 milligrams a day, against 20 milligrams in the lowest group. The study did not compare sweeteners with sugar.
What should readers do with this information?
The study does not change existing guidance and does not recommend stopping low- and no-calorie sweeteners. Its author has called for more research, including research into other sugar substitutes such as applesauce, honey, maple syrup and coconut sugar. Anyone concerned, or who has diabetes, should discuss their own situation with a doctor or another qualified health professional.
Sources
- Neurology, the medical journal of the American Academy of Neurology — study first published 2025, Neurology 2025;105(7), DOI 10.1212/WNL.0000000000214023; paper corrected and replaced July 2026; American Academy of Neurology release updated late October 2026.
- Men's Journal — news coverage, 2–3 November 2026.
- ScienceDaily — news coverage, 29 October–3 November 2026.
- Fox News Digital — news coverage, 29 October–3 November 2026.
- Medical Dialogues — news coverage, 29 October–3 November 2026.
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