Yes, research suggests that high consumption of artificial sweeteners may be associated with an increased risk of cognitive decline and dementia — though it is important to understand what that means and what it does not. A landmark 2025 study published in the journal Neurology tracked nearly 13,000 people over roughly eight years and found that those who consumed the most artificial sweeteners experienced cognitive decline 62% faster than those who consumed the least.
To put that in concrete terms: someone who regularly drinks a single can of diet soda per day — which typically contains 200 to 300 mg of aspartame — may be consuming enough to fall into the highest-risk category studied. This article covers what the major studies found, which sweeteners appear most concerning, who is at greatest risk, and what the significant limitations of this research mean for how you should actually interpret these findings. We also look at practical steps for people concerned about brain health, and what the science still does not know.
Table of Contents
- What Does the Research Actually Show About Artificial Sweeteners and Dementia Risk?
- Which Artificial Sweeteners Are Most Linked to Cognitive Decline?
- Who Is Most at Risk — Age, Diabetes, and Other Factors
- What Should You Actually Do If You Consume Artificial Sweeteners?
- How Strong Is the Evidence — and What Are the Real Limitations?
- The Broader Pattern — Brain Health and Processed Food Ingredients
- Where the Research Is Headed
- Conclusion
- Frequently Asked Questions
What Does the Research Actually Show About Artificial Sweeteners and Dementia Risk?
The most comprehensive recent evidence comes from a study published October 7, 2025 in Neurology, the journal of the American Academy of Neurology. Researchers followed 12,772 people over approximately eight years, examining consumption of seven artificial sweeteners: aspartame, saccharin, acesulfame-K, erythritol, sorbitol, xylitol, and tagatose. Participants in the highest consumption tier — averaging around 191 mg per day — showed cognitive decline 62% faster than those in the lowest consumption group. The researchers calculated that this difference is roughly equivalent to 1.6 additional years of brain aging. To put 191 mg in perspective: a standard 12-ounce can of diet soda sweetened with aspartame typically contains 200 to 300 mg. That means someone drinking one diet soda daily is close to or at the threshold that the study associated with accelerated decline.
This is not a fringe amount. It is a consumption level that tens of millions of people reach without a second thought. Earlier research pointed in a similar direction. The 2017 Framingham Heart Study, published in the journal Stroke by the American Heart Association, found that people who drank diet soda daily had a hazard ratio of 2.89 for Alzheimer’s disease compared to non-consumers — nearly three times the risk. The same study found a hazard ratio of 2.96 for ischemic stroke. While hazard ratios from observational studies need to be read carefully, those are not small numbers.
Which Artificial Sweeteners Are Most Linked to Cognitive Decline?
The 2025 Neurology study examined seven sweeteners as a group, and the findings applied to the category broadly rather than isolating one compound as uniquely dangerous. Aspartame, one of the most widely consumed artificial sweeteners in the world, has received the most scrutiny historically. It is metabolized in the body into phenylalanine, aspartic acid, and methanol — compounds that can cross the blood-brain barrier and, in theory, affect neurotransmitter function. Researchers have hypothesized that chronic low-level exposure could disrupt serotonin and dopamine pathways, which are important not just for mood but for memory and executive function. Erythritol and xylitol, which are often marketed as more “natural” sugar alcohols, were also included in the 2025 study’s findings.
This is worth noting because many consumers have shifted toward these alternatives under the assumption that they are categorically safer than older synthetic sweeteners like aspartame or saccharin. The research does not support that assumption. If you are avoiding aspartame but loading up on erythritol-sweetened protein bars, you may not be meaningfully reducing your exposure to the compounds associated with cognitive risk. However, a critical limitation applies here: the study did not parse out individual sweeteners with enough statistical power to say definitively that sweetener X causes more harm than sweetener Y. The findings reflect aggregate consumption. That means it is premature to single out one compound as the villain while treating others as safe.
Who Is Most at Risk — Age, Diabetes, and Other Factors
One of the more striking findings from the 2025 Neurology study is that the association between artificial sweetener consumption and cognitive decline was substantially stronger in people under 60. Younger adults in the high-consumption group showed faster declines in verbal fluency and overall cognition. By contrast, no significant link was found in people over 60. This is an unusual pattern that researchers have not fully explained, and it warrants caution before drawing sweeping conclusions either way. The association was also stronger in people with diabetes.
This is a notable intersection because people with diabetes are often the heaviest users of artificial sweeteners — they are advised to reduce sugar intake, and sweeteners are frequently recommended as a substitute. If the research holds up, the population being told to use these products most aggressively may be among the most vulnerable to their potential cognitive effects. That is a real tension that clinicians and patients should be aware of. For people over 60 — the age group most commonly associated with dementia risk — the 2025 study found no significant link. This does not mean older adults are protected, and it does not mean the Framingham findings (which did not segment by age in the same way) are irrelevant. But it does suggest that the mechanisms at play, if any, may be more complex than a simple dose-response relationship across all ages.
What Should You Actually Do If You Consume Artificial Sweeteners?
The honest answer is that the science is not at the stage where any researcher can tell you precisely how many milligrams of aspartame per day is safe or unsafe for your brain. What the research does provide is a reasonable basis for caution, particularly if you are a heavy consumer. Consider where artificial sweeteners are concentrated in your diet: diet sodas, sugar-free energy drinks, protein shakes, low-calorie yogurts, sugar-free gum, and many packaged “diet” foods. A person who drinks two diet sodas a day, uses a sweetener packet in their morning coffee, and eats a couple of protein bars could easily be consuming several times the 191 mg daily average that fell into the high-risk category in the 2025 study. If you are looking for practical steps, reducing diet soda is the most direct lever.
Plain water, sparkling water without sweeteners, unsweetened tea, or coffee without sweetener substitutes are the clearest alternatives. For people who need sweetener for palatability, small amounts of plain sugar or honey — which the body processes very differently than synthetic compounds — may actually be preferable from a brain health standpoint, though this comes with obvious tradeoffs for blood sugar management, particularly for diabetics. The tradeoff worth naming explicitly: artificial sweeteners were introduced and promoted as a healthier alternative to sugar. For metabolic and dental health, there is evidence supporting that trade. For brain health specifically, the picture is now more complicated. Swapping one can of regular soda (high in sugar) for one can of diet soda (high in aspartame) is not a straightforwardly healthy trade when dementia risk is part of the equation.
How Strong Is the Evidence — and What Are the Real Limitations?
Every major study in this area, including the 2025 Neurology paper and the Framingham Heart Study, is observational. That is not a minor caveat. Observational studies track behavior and outcomes but cannot establish that one thing caused the other. The participants were not randomly assigned to drink diet soda; they chose their own consumption habits, and those habits correlate with dozens of other lifestyle factors — stress levels, overall diet quality, sleep, exercise, education, income — that also affect cognitive aging. Reverse causation is another legitimate concern.
It is possible that people who are already experiencing early, subclinical cognitive decline begin modifying their diets in ways that happen to include more artificially sweetened foods, rather than the sweeteners causing the decline. Early dementia can affect judgment, food preferences, and daily routines long before a clinical diagnosis is made. If that process is underway, a study tracking diet and later cognitive outcomes might misread the direction of causation. Researchers acknowledge they have not ruled out confounding lifestyle factors, and no randomized controlled trial exists — or is likely to be conducted — that could definitively settle this question. What that means practically is that the findings justify informed caution and warrant further research, but they do not justify panic or sweeping clinical recommendations. Anyone who tells you the science definitively proves that artificial sweeteners cause dementia is overstating what the evidence shows.
The Broader Pattern — Brain Health and Processed Food Ingredients
Artificial sweeteners do not exist in isolation. They are almost always consumed as part of ultra-processed food and beverage products that contain a range of other compounds — artificial flavors, colorings, emulsifiers, and preservatives — with their own emerging literature on systemic health effects. The brain, as the most metabolically active organ in the body, is particularly sensitive to chronic low-level chemical exposures over decades.
The pattern emerging in brain health research is one of cumulative risk: no single ingredient is likely to cause dementia on its own, but a dietary pattern dominated by ultra-processed products appears consistently in studies as a risk factor for cognitive decline. Artificial sweeteners may be one piece of that picture. A person who eats mostly whole foods and occasionally has a diet soda is probably not in the same risk category as someone whose daily intake is built around artificially sweetened beverages and packaged diet foods.
Where the Research Is Headed
The 2025 Neurology findings have intensified interest in the mechanisms by which artificial sweeteners might affect the brain. Current hypotheses focus on gut-brain axis disruption — specifically, the role sweeteners play in altering the gut microbiome, which is now understood to communicate with the brain through multiple pathways.
Changes in microbiome composition have been linked in animal studies to neuroinflammation and amyloid accumulation, both of which are implicated in Alzheimer’s pathology. Future research will likely attempt to tease apart individual sweeteners, consumption patterns, and genetic vulnerabilities — including APOE4 status, the most established genetic risk factor for late-onset Alzheimer’s. For now, the honest summary is that the science has moved from “probably harmless” to “warrants serious investigation,” and that shift is meaningful enough to inform dietary choices even before definitive causation is established.
Conclusion
The weight of current evidence suggests that high consumption of artificial sweeteners is associated with faster cognitive decline and a meaningfully elevated risk of Alzheimer’s disease. The 2025 Neurology study — tracking nearly 13,000 people over eight years — found that consuming around 191 mg per day, roughly one can of diet soda, was associated with cognitive aging that was the equivalent of 1.6 additional years of brain aging. The Framingham Heart Study found that daily diet soda drinkers had nearly three times the risk of Alzheimer’s disease compared to non-consumers. These findings are consistent, large in scale, and have been replicated across different methodologies.
That said, none of this research proves causation. All of it is observational, and reverse causation remains a legitimate alternative explanation. The practical implication is not to eliminate all sweeteners in a panic, but to take a clear-eyed look at how much you are consuming and whether it is worth revisiting. If your daily routine includes multiple artificially sweetened products, reducing that load — particularly from diet sodas — is a reasonable, low-cost step for brain health that carries little downside. The science is not finished, but it has moved far enough that waiting for certainty before acting seems like the less prudent choice.
Frequently Asked Questions
Is diet soda the main source of artificial sweetener exposure?
Diet soda is the single most concentrated source for most people. A standard 12-ounce can of aspartame-sweetened diet soda contains 200 to 300 mg of aspartame — more than the 191 mg daily average that fell into the high-risk group in the 2025 Neurology study. However, artificial sweeteners are also present in sugar-free gum, protein bars and shakes, flavored yogurts, sugar-free syrups, and many packaged “diet” or “light” products. Heavy consumers often accumulate significant daily amounts across multiple sources.
Which artificial sweeteners were studied in the 2025 Neurology research?
The 2025 study examined seven sweeteners: aspartame, saccharin, acesulfame-K, erythritol, sorbitol, xylitol, and tagatose. The findings applied to high consumption of this group broadly. The study did not have statistical power to definitively rank individual sweeteners by harm.
Does this research apply equally to all ages?
No. The 2025 study found that the association between high sweetener consumption and faster cognitive decline was most pronounced in people under 60. No significant link was found in people over 60. The reasons for this age difference are not yet understood.
Are people with diabetes at higher risk from artificial sweeteners?
The 2025 Neurology study found the association was stronger in people with diabetes. This is particularly concerning because people with diabetes are often the heaviest users of artificial sweeteners as a sugar substitute.
Do these studies prove that artificial sweeteners cause dementia?
No. All major studies in this area are observational, meaning they track associations but cannot establish causation. Reverse causation — where early cognitive decline leads to dietary changes rather than the reverse — has not been ruled out. The findings justify caution but do not constitute proof of a causal link.
What are the safest alternatives to artificial sweeteners?
Plain water, unsweetened sparkling water, unsweetened tea, and black coffee are the most straightforward alternatives. Small amounts of regular sugar or honey avoid the synthetic compounds associated with cognitive risk, though they come with blood sugar tradeoffs, especially for people with diabetes. There is no current evidence that any sweetener, natural or artificial, is definitively safe in high amounts from a brain health perspective.
