Six Common Sweeteners Linked to 62% Faster Cognitive Decline

If you swapped sugar for a "zero calorie" sweetener years ago to manage your weight or blood sugar, a new 8-year study is worth a second look, especially if you already suspect your gut and your brain are more connected than you'd like. Researchers at the University of Sao Paulo tracked nearly 13,000 Brazilian adults and found that the heaviest users of common sweeteners like aspartame and saccharin showed measurably faster declines in memory and thinking over time than the lightest users. It's an early, unproven finding, but it lands at a moment when sweeteners are already under scrutiny for what they might be doing to the gut, so the brain angle adds a new thread worth watching.

Key takeaways:

• An 8-year cohort study of 12,772 Brazilian adults found the highest sweetener consumers had a 62% faster decline in overall thinking and memory than the lowest consumers, roughly 1.6 extra years of brain aging.
• Six of the seven sweeteners studied, aspartame, saccharin, acesulfame K, erythritol, xylitol and sorbitol, were linked to faster decline; tagatose was the exception.
• The effect was strongest in adults under 60 and in people with diabetes.
• This is an observational study and cannot prove sweeteners caused the cognitive changes; the full peer-reviewed paper was not independently reviewed for this article.

Study Links Six Common Sweeteners to Faster Cognitive Decline

Adults who consumed the most low- and no-calorie sweeteners experienced meaningfully faster cognitive decline than adults who consumed the least, according to an 8-year prospective study published in the journal Neurology by researchers including Dr. Claudia Kimie Suemoto. Comparing the highest intake group (191 milligrams a day) with the lowest (20 milligrams a day), the study found a 62% faster decline in overall thinking and memory skills, an effect the researchers estimated was comparable to roughly 1.6 additional years of brain aging. A middle-consumption group also showed faster decline, about 35% faster, equivalent to roughly 1.3 extra years. Six of the seven sweeteners tracked, aspartame, saccharin, acesulfame K, erythritol, xylitol and sorbitol, were associated with the pattern; tagatose, a less common sugar substitute, was not.

Why This Matters if You're Under 60 or Managing Diabetes

The association was strongest in two groups: adults younger than 60 and people with diabetes, populations that are also among the heaviest everyday users of sugar substitutes for weight or blood sugar management. For someone in either group who has swapped soda, coffee packets or "diet" snacks for sweetened versions as a health strategy, this is a reason to pay attention rather than panic, since the study does not identify a safe or unsafe dose, only a statistical pattern across two groups defined by relative intake. It also isn't the first cohort to raise the question: an earlier Framingham Heart Study analysis found that people who drank artificially sweetened beverages daily had a higher risk of stroke and dementia over a decade of follow-up, though that study did not find the same link for sugar-sweetened drinks. It's also a useful data point for anyone already managing a gut condition and wondering whether sweeteners cut both ways; the study itself only measured cognition, not gut bacteria, but it arrives alongside a separate and growing body of research on how artificial sweeteners alter the gut microbiota (the community of bacteria living in the digestive tract), one of several pathways researchers are exploring for how gut chemistry might influence the brain.

An 8-Year Cohort of Nearly 13,000 Brazilian Adults

The findings come from the ELSA-Brasil cohort, a long-running Brazilian study that followed 12,772 adults with an average age of 52 for approximately eight years, comparing self-reported sweetener intake against changes in cognitive test performance over that period. The size and length of follow-up let the researchers separate a high-, middle-, and low-intake group and track how each group's cognitive trajectory diverged over time, rather than relying on a single snapshot comparison. Dr. Suemoto, in comments accompanying the study, said that "while our study cannot prove causation, this magnitude of association raises concern," a framing that captures both the strength of the pattern and its limits.

Gut-Brain Connections Are a Growing, Still-Unsettled Research Thread

This study did not test how sweeteners affect the gut microbiome or whether any gut-related pathway explains the cognitive link, so any gut-brain-axis (the communication network linking gut bacteria and the brain) explanation here is speculation, not a finding of this paper. What is established elsewhere is that some of the same sweeteners tracked in this study, including saccharin, have been shown in separate laboratory research to alter gut bacteria composition and gut-to-brain signaling in ways that could plausibly connect to cognition, though that mechanistic work has not yet been tied directly back to this cohort's results. An independent geriatric specialist not involved in the study, Dr. Kamal Wagle, cautioned that "this study shows a link, not a cause," a reminder that the cognitive findings and the microbiome mechanism are, for now, two separate bodies of evidence rather than one proven chain.

What This Study Cannot Tell You

This is observational data, not a controlled trial, so it cannot rule out that other factors related to why people reach for sweeteners in the first place, existing metabolic conditions, dietary patterns, or health-consciousness generally, explain part of the link rather than the sweeteners themselves. The study also does not name a funder, and the Calorie Control Council, an industry group representing low- and no-calorie sweetener makers, publicly pushed back on the findings, emphasizing that the data show correlation rather than causation and questioning the reliability of self-reported diet; that critique is a third-party industry response, not a disclosed conflict tied to the study itself. The full peer-reviewed paper sits behind a subscription paywall and was not independently obtained for this article; the numbers above are drawn from the study's own published findings as reported across multiple outlets that covered its release, cross-checked against each other for consistency.

Common Questions

Which sweeteners were linked to faster cognitive decline? Aspartame, saccharin, acesulfame K, erythritol, xylitol and sorbitol were associated with faster decline in the study; tagatose was the one sweetener tested that was not.

Does this study prove sweeteners cause cognitive decline? No. It is an observational cohort study, so it can show that heavier sweetener use and faster cognitive decline occurred together, not that one caused the other.

Who showed the strongest link in the study? Adults younger than 60 and people with diabetes showed the clearest association between sweetener intake and faster cognitive decline.

Did the study look at the gut microbiome? No. This study measured cognitive test performance, not gut bacteria. Any gut-brain connection is based on separate research on sweeteners and the microbiome, not on this study's own data.

References

1. Jotham Suez, Tal Korem, David Zeevi, et al. (2014). Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. https://doi.org/10.1038/nature13793
2. Roberto Coccurello (2025). Disrupting the Gut–Brain Axis: How Artificial Sweeteners Rewire Microbiota and Reward Pathways. International Journal of Molecular Sciences. https://doi.org/10.3390/ijms262010220