A major new study reveals that consuming low-calorie sweeteners like aspartame and erythritol is associated with accelerated cognitive decline—especially in people under 60.
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Introduction
For millions of people worldwide, low-calorie sweeteners seem like a guilt-free way to enjoy sweetness without the calories. They’re in diet sodas, sugar-free yogurts, protein bars, and countless “light” products. But a major new study published in the journal Neurology suggests that this seemingly healthy swap might come with a hidden cost—one that affects the most vital organ in your body: your brain.
The research, which followed nearly 13,000 adults over eight years, found a clear link between consuming certain artificial sweeteners and a faster rate of cognitive decline. This decline wasn’t just a slight dip; it was equivalent to about 1.6 years of additional brain aging for the highest consumers.
A Closer Look at the Study
This isn’t a small-scale or short-term investigation. The study, known as the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), is a large, ongoing project tracking the health of civil servants across six Brazilian cities.
Researchers analyzed data from 12,772 participants with an average age of 52. At the start of the study, participants filled out detailed questionnaires about their diets, which allowed researchers to estimate their intake of seven common low- and no-calorie sweeteners (LNCS):
- Artificial Sweeteners: Aspartame, Saccharin, Acesulfame-K
- Sugar Alcohols: Erythritol, Xylitol, Sorbitol
- A Natural Sweetener: Tagatose
Over the following eight years, the participants’ cognitive abilities were tested three times. These tests measured key functions like memory, verbal fluency, and processing speed.
After accounting for other factors like age, sex, high blood pressure, and cardiovascular disease, the researchers analyzed whether sweetener consumption was linked to how these cognitive functions changed over time.
The results were striking.
The Findings: A Clear Link, Not a Guarantee
The study did not claim that sweeteners cause cognitive decline; it found a strong association. However, the patterns were clear and concerning.
1. Faster Decline in Midlife
Participants under the age of 60 who consumed the highest amounts of sweeteners showed a 62% faster decline in overall thinking and memory skills than those who consumed the lowest amounts.
Those in the middle consumption group fared better than the highest group but still experienced a 35% faster decline than the lowest group.
This means that even moderate consumption was associated with a measurable difference in cognitive aging over 8 years.
2. The Age Factor: Midlife is Critical
One of the most surprising findings was that the association was significant only among people under 60. No such link was found for participants aged 60 and older.
Why? Experts believe this fits with what we know about dementia risk factors like hypertension, obesity, and diabetes—they exert their strongest effects in midlife.
“By the time someone comes for their first Medicare checkup, the horse may already have left the barn,” noted one expert not involved in the study, emphasizing the importance of midlife exposures for long-term brain health. It’s less that sweeteners are safe for older people, and more that the damage may have already been set in motion decades earlier.
3. Specific Areas of the Brain Affected
The effects weren’t uniform across all mental abilities. The decline was most pronounced in two specific areas:
- Verbal Fluency: This is the ability to quickly and efficiently recall and produce words, which is a key indicator of healthy brain function. High consumers had a 110% to 173% faster rate of decline in verbal fluency compared to low consumers.
- Global Cognition and Memory: This represents overall thinking skills and the ability to remember information. Many of the individual sweeteners were specifically linked to faster declines in memory.
4. Which Sweeteners Are the Culprits?
Of the seven sweeteners analyzed, six were linked to faster cognitive decline: aspartame, saccharin, acesulfame-K, erythritol, xylitol, and sorbitol. These declines were most notable in memory and verbal fluency.
Tagatose was the only sweetener studied that showed no association with cognitive decline. However, the researchers cautioned that tagatose consumption in this population was very low, so no firm conclusions could be drawn about its safety.
5. A Stronger Link for People with Diabetes
For people with diabetes, the association was even more pronounced. They showed a faster decline in memory and global cognition associated with high sweetener intake. This is particularly concerning because people with diabetes often rely heavily on sugar substitutes and are already at a higher risk for cognitive issues.
The lead author suggested that this could be a “double hit” scenario: an already vulnerable brain being exposed to a compound that might promote neuroinflammation.
To put these numbers into perspective, the average consumption for the highest group was about 191 mg/day of combined sweeteners.
For aspartame, this is roughly the equivalent of one can of diet soda. This suggests that the levels associated with faster decline are well within the range of what many people consume daily.
What Does This Mean for You?
- Stay Informed, But Don’t Panic. This is one large, well-conducted study, but it shows an association, not definitive causation. The prudent path is to view these findings as a strong reason to reduce or eliminate LNCS from your diet, especially if you fall into a higher-risk group, while awaiting further research.
- For Everyone: Limit Consumption. You don’t need to panic over an occasional diet soda, but the study’s lead author advises it is “wise to limit consumption as much as possible, ideally avoiding daily use.” The average intake linked to faster decline was roughly equivalent to just one can of diet soda per day.
- Pay Attention in Midlife. The association was strongest for people under 60. This suggests that dietary choices in your 40s and 50s may have a significant impact on your long-term brain health. It is a critical window for prevention.
- Be Especially Cautious if You Have Prediabetes or Diabetes. The link between LNCS and faster cognitive decline was even stronger in people with diabetes. Since these individuals are already at higher risk for cognitive issues, it is prudent to avoid LNCS and instead focus on whole-food-based approaches to manage blood sugar.
- Avoid LNCS if You Have Hypertension. Given that hypertension already damages the brain’s blood vessels, adding a potential neuro-inflammatory or vascular insult from LNCS is an unnecessary risk. A diet like the DASH diet, which is naturally low in added sugars and sweeteners, is a much safer choice.
- Avoid LNCS if You Are Managing Obesity. Chronic inflammation, common in obesity, is a driver of cognitive decline. Adding the potential inflammatory effects of LNCS is counterproductive. Moreover, these sweeteners may perpetuate sugar cravings, making long-term weight management more difficult.
- Focus on Whole Foods and Natural Flavors. The study reinforces the broader message of shifting toward a balanced diet. Instead of relying on artificial substitutes, try using natural options like fruit, cinnamon, vanilla, or other spices to add flavor to your foods and beverages. This approach supports a healthy gut microbiome, which is increasingly linked to brain health.
- Not All Sweeteners Are Equal. Of the seven studied, six (aspartame, saccharin, acesulfame-K, erythritol, xylitol, and sorbitol) were associated with faster cognitive decline. Tagatose did not, but consumption was too low to draw firm conclusions about its safety. Until more is known, it is best to be cautious with all of them.
- Stay Informed, But Don’t Panic. This is one large, well-conducted study, but it shows an association, not definitive causation. The prudent path is to view these findings as a strong reason to reduce or eliminate LNCS from your diet, especially if you fall into a higher-risk group, while awaiting further research.
What’s the Biological Link?
The study authors and other experts have proposed several theories for how artificial sweeteners could impact the brain. It’s important to note that these are still hypotheses, but they are grounded in existing biological research.
- Gut Microbiome Disruption: Your diet is the primary driver of the composition of your gut microbiome—the trillions of bacteria that live in your digestive tract. Artificial sweeteners have been shown to change this composition, potentially promoting a less healthy balance of bacteria. An unhealthy gut can trigger systemic inflammation, which can affect the brain and impair cognitive function.
- Neuroinflammation: Research in animal models has shown that when mice are given large amounts of sweeteners, they develop neuroinflammation and neurodegeneration. This suggests that these compounds might directly trigger an inflammatory response in the brain’s immune cells, known as microglia, shifting them into a damaging, inflammatory state that increases the risk of cognitive decline.
- Blood-Brain Barrier Disruption: Some research suggests that sweeteners could contribute to dysfunction in the microvascular system, which includes the delicate network of blood vessels in the brain .
The Big Picture: More Questions Than Answers
This study is a significant piece of a growing puzzle. It’s the largest and longest prospective study to date investigating this specific link. However, it is just one study, and it has important limitations.
- Self-Reported Data: The study relied on participants to accurately report what they ate, which is a common source of error in nutritional research.
- Observational Design: The study shows a link, not a cause-and-effect relationship. It’s possible that people who consume more sweeteners also have other lifestyle factors that contribute to cognitive decline, and despite the researchers’ best efforts, they couldn’t control for everything.
- Not All Sweeteners Included: For instance, sucralose, a very common sweetener, was not included in the study.
Experts agree that while these results are “compelling,” they need to be confirmed by further research.
However, for the educated layman, the takeaway is clear: the “health halo” around artificial sweeteners is fading. The modern habit of replacing sugar with calorie-free alternatives might not be the harmless workaround it was once thought to be, and it may come with significant long-term consequences for our most precious asset: our brain.
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About Dr. Jesse Santiano, MD
Dr. Santiano is a retired internist and emergency physician with extensive clinical experience in metabolic health, cardiovascular prevention, and lifestyle medicine. He reviews all medical content on this site to ensure accuracy, clarity, and safe application for readers. This article is for educational purposes and is not a substitute for personal medical care.
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Reference:
- Gonçalves NG, Martinez-Steele E, Lotufo PA, Bensenor I, Goulart AC, Barreto SM, Giatti L, de Faria CP, Molina MDCB, Caramelli P, Marchioni DM, Suemoto CK. Association Between Consumption of Low- and No-Calorie Artificial Sweeteners and Cognitive Decline: An 8-Year Prospective Study. Neurology. 2025 Oct 7;105(7):e214023. doi: 10.1212/WNL.0000000000214023. Epub 2025 Sep 3. Erratum in: Neurology. 2025 Dec 9;105(11):e214393. doi: 10.1212/WNL.0000000000214393. Erratum in: Neurology. 2026 Aug 25;107(4):e218380. doi: 10.1212/WNL.0000000000218380. PMID: 40902134. [abstract]
Disclaimer:
This article is for educational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician before making health decisions based on the TyG Index or other biomarkers.
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