A new long-term study published in Neurology reveals that adults who consume the highest amounts of low- and no-calorie sweeteners experience a 62 percent faster decline in memory and thinking skills—an aging effect comparable to 1.6 extra years. The observational research tracked nearly 13,000 adults over eight years.
The São Paulo Study: Seven Sweeteners and Eight Years of Tracking
But a major study led by researchers at the University of São Paulo in Brazil examined seven popular sugar substitutes to see how they affect long-term brain health. The research followed 12,772 adults living across Brazil, monitoring participants for approximately eight years with an average starting age of 52.
Participants completed detailed food questionnaires at the start of the project to record their eating and drinking habits over the previous year. Researchers then divided the cohort into three consumption groups. People in the lowest group averaged 20 milligrams per day of sweeteners, while those in the highest group averaged 191 milligrams daily. To put that top tier into perspective, the amount of aspartame consumed by the highest group was roughly equivalent to the aspartame found in one can of diet soda a day.
Throughout the monitoring period, participants underwent periodic cognitive assessments that measured verbal fluency, working memory, word recall, and processing speed. When researchers adjusted for age, sex, high blood pressure, and cardiovascular disease, a distinct pattern emerged. Individuals in the highest consumption group experienced a 62% faster decline in mental performance over the eight years compared to those in the lowest group. The research team calculated that this gap was equivalent to about 1.6 extra years of brain aging.
Middle-tier consumers were not immune either. Participants in the middle consumption group experienced a decline that was 35% faster than those in the lowest group, a difference comparable to about 1.3 extra years of aging.
“Low- and no-calorie sweeteners are often seen as a healthy alternative to sugar, however our findings suggest certain sweeteners may have negative effects on brain health over time.”
Claudia Kimie Suemoto, MD, PhD, University of São Paulo
Which Sweeteners Were Examined and What the Data Showed
The study cast a wide net across the grocery store aisle, investigating aspartame, saccharin, acesulfame K, erythritol, xylitol, sorbitol, and tagatose. These compounds are frequent ingredients in flavored waters, soft drinks, energy drinks, yogurts, and low-calorie desserts, as well as standalone packets used for coffee and tea. Aspartame is common in products like Diet Coke and Diet Pepsi, saccharin serves as the primary sweetener in Sweet’N Low, and erythritol is a staple in keto-friendly foods. Sorbitol appeared in the largest quantities among individual participants, averaging 64 milligrams per day.
When the research team analyzed the ingredients individually, six of the seven sweeteners were linked to faster cognitive decline, particularly in memory measures. Tagatose was the only substance in the group that showed no association with accelerated mental aging.
Experts emphasize that the research demonstrates an association rather than direct causation. Memory loss is rarely caused by just one food or drink
, explains Dr. Amit Kumar Agarwal, Senior Consultant in Neurology at Amrita Hospital in Faridabad, noting that cognitive decline develops over years of interaction among genetics, aging, vascular health, sleep quality, physical activity, and nutrition.
Vulnerable Groups: Why Adults Under 60 and People With Diabetes Face Higher Risks
The impact of sugar substitutes did not hit every demographic equally. Age and underlying health status shifted the results in notable ways. Among study participants younger than 60, high sweetener intake was tied to faster declines in verbal fluency and overall cognitive performance. Researchers did not observe the same pattern among participants older than 60.
Additionally, the link between sweetener consumption and cognitive decline proved significantly stronger among people with diabetes. Clinicians point out that individuals managing diabetes rely more heavily on artificial sweeteners to avoid foods and beverages that cause rapid blood sugar spikes.
“While we found links to cognitive decline for middle-aged people both with and without diabetes, people with diabetes are more likely to use artificial sweeteners as sugar substitutes.”
Claudia Kimie Suemoto, MD, PhD, study author
That intersection carries substantial public health weight. In the United States alone, approximately 40.1 million people—roughly 1 in 8 residents—live with diabetes. Dr. Agarwal notes that brain health deserves particular caution for individuals who already face elevated risks of cognitive decline, such as those with diabetes, obesity, hypertension, or a history of stroke.
Broader Context From the Northern Manhattan Study
The Brazilian cohort findings align with other long-running investigations into sweetened beverages and neurological health. A separate analysis from the Northern Manhattan Study (NOMAS), published in the Journal of Alzheimer’s Disease and led by researchers at the University of Miami Miller School of Medicine, investigated 947 participants to evaluate long-term cognitive trajectories.
That study found that each additional diet soda consumed per day was linked to a 34% increase in dementia risk among its cohort. Dr. Hannah Gardener, a senior author on the NOMAS analysis, emphasized that diet soda is likely not a healthy alternative to regular sugar-sweetened soda when protecting brain health over decades.
Both research teams acknowledge important study limitations. The São Paulo evaluation relied on participants recalling and reporting their own dietary habits, and researchers did not test every artificial sweetener currently available on the market. As scientists continue investigating potential biological pathways—such as how artificial sweeteners might alter gut bacteria, glucose metabolism, or reward pathways—health professionals suggest sticking to simpler alternatives like plain water, unsweetened buttermilk, coconut water, or fresh homemade drinks.
