Not So Sweet: How Popular Sugar Substitutes May Accelerate Brain Aging

Key takeaways

• In a large, eight‑year study of nearly 13,000 adults, higher intake of several common sugar substitutes was linked to faster declines in memory and thinking.

• The highest consumers showed cognitive aging roughly 1.6 years “older” than the lowest consumers, even after accounting for age, blood pressure, and other factors.

• Not all sweeteners behaved the same: six were associated with faster decline, while one (tagatose) was not.

Researchers followed adults in Brazil with an average age of 52 and tracked their diet and cognitive performance over time. At baseline, participants reported what they had eaten and drunk in the previous year and were grouped into low, medium, and high sweetener‑intake categories based on total daily milligrams. People in the lowest group averaged about 20 mg/day of sweeteners, while those in the highest group averaged around 191 mg/day—roughly the aspartame content of one can of diet soda, plus other sweeteners from foods and drinks.

Participants then completed cognitive assessments at the beginning, midpoint, and end of the roughly eight‑year follow‑up. These tests captured several domains of brain function: verbal fluency, working memory, word recall, and processing speed. The question wasn’t “do sweeteners cause damage?” but “do people who regularly consume more of them tend to show different aging patterns in these abilities?”

How much faster did thinking change?

After adjusting for age, sex, high blood pressure, cardiovascular conditions, and other relevant factors, the pattern was clear: those in the highest‑intake group experienced a 62% faster decline in overall thinking and memory than those in the lowest‑intake group. Statistically, that difference corresponded to about 1.6 extra years of cognitive aging over the study period.

People in the middle‑intake group weren’t off the hook either; their decline was about 35% faster than the lowest group, equivalent to roughly 1.3 additional years of aging. The association was most pronounced in verbal fluency and overall cognitive performance, particularly among adults under 60 and those living with diabetes, who tend to use sugar substitutes more frequently.

Not all sweeteners behaved the same

The study examined seven widely used low‑ or no‑calorie sweeteners: aspartame, saccharin, acesulfame K, erythritol, xylitol, sorbitol, and tagatose. These compounds are common in flavored waters, soft drinks, energy drinks, “light” yogurts, low‑calorie desserts, and other ultra‑processed products, as well as in tabletop packets.

When researchers broke the data down by individual sweetener, six of them—aspartame, saccharin, acesulfame K, erythritol, sorbitol, and xylitol—were associated with faster declines in overall cognition, especially memory. Tagatose was the outlier: it did not show a link to faster cognitive aging in this cohort. That doesn’t mean tagatose is definitively “safe” or the others are definitively “harmful”; it means that, in this particular dataset, its intake didn’t track with accelerated decline the way the others did.

Important caveats 

The authors are clear that this is observational research. It reveals a relationship between higher sweetener consumption and faster cognitive aging, but it does not prove that the sweeteners themselves are the cause. Self‑reported food data can be imperfect, and people who consume more sweeteners may differ from low consumers in other ways that affect brain aging. The study also didn’t include every artificial sweetener on the market.

For a longevity‑focused lens, the signal is still worth noting: swapping sugar for certain low‑ or no‑calorie substitutes may not be a free cognitive trade, especially for middle‑aged adults and those using large amounts over many years. Future work will need to test mechanisms and compare these ingredients to other “refined sugar alternatives” like fruit purées, honey, agave, maple syrup, or coconut sugar. In the meantime, this study nudges the conversation away from “zero calories equals harmless” and toward a more nuanced view of how sweetening strategies may intersect with long‑term brain health.

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