A recent study has uncovered a significant link between the consumption of artificial sweeteners and an accelerated rate of cognitive decline and brain aging. While researchers continue to explore the precise mechanisms, initial theories suggest that these sugar substitutes may induce inflammation and disrupt the gut microbiome, potentially harming brain health. This new research adds to a growing body of evidence urging individuals to reconsider their reliance on sweet and processed foods.

Published on September 3 in the journal Neurology, the study, led by Dr. Claudia Kimie Suemoto, an associate professor of geriatrics at the University of São Paulo Medical School in Brazil, found that individuals with the highest intake of six specific artificial sweeteners experienced the most pronounced declines in thinking and memory. These declines were equivalent to approximately 1.6 years of additional brain aging compared to those who consumed fewer sweeteners. Dr. Suemoto clarified that this doesn't imply immediate memory issues after an occasional diet soda but rather suggests that frequent consumption could lead to the brain aging at a quicker pace, thereby increasing the long-term risk of earlier or more severe cognitive impairment.

The comprehensive study tracked data from 12,772 Brazilian adults, with an average age of 52 at the outset. Participants completed detailed questionnaires about their dietary habits over the preceding year. The research specifically focused on seven low- and no-calorie sweeteners commonly found in various products like sodas, low-calorie desserts, yogurts, and standalone packets: Aspartame, Saccharin, Xylitol, Erythritol, Sorbitol, Tagatose, and Acesulfame K. Participants were categorized into groups based on their daily intake: 'Low' (around 20 milligrams), 'Moderate' (about 66 mg), and 'High' (approximately 191 mg, which is roughly equivalent to one can of diet soda).

Over an eight-year period, these participants underwent a series of cognitive assessments, including tests for verbal fluency (the speed at which they could articulate words within a given category), word recall, general memory, and information processing speed. The findings revealed a strong connection between higher sweetener intake and worse cognitive performance. Compared to the group with minimal sweetener consumption, the moderate intake group exhibited a 35% faster rate of memory and thinking decline and a 110% faster rate of verbal fluency decline. The high consumption group showed an even more drastic impact, with a 62% faster rate of memory and thinking decline and a 173% faster rate of verbal fluency decline.

Interestingly, this concerning link between low- or no-calorie sweeteners and cognitive decline was observed predominantly in individuals under the age of 60. Theresa Gentile, MS, RDN, highlighted the significance of this research, noting that it represents one of the largest studies to connect multiple different sweeteners to measurable cognitive decline over time. When examining individual sweeteners, the data indicated that while tagatose was not associated with cognitive decline, the other six sweeteners tracked showed a similar adverse effect, with no single one appearing significantly worse than another.

Although the study’s authors emphasize that their findings do not conclusively prove causation, experts have put forth several theories regarding how sugar substitutes might impact brain health. Rebecca Solch-Ottaiano, PhD, suggests that diet is a major determinant of the gut microbiome's composition. Therefore, increased consumption of sugar substitutes could alter the gut microbiome and potentially lead to inflammation, although further research is required to confirm this. David Perlmutter, MD, a neurologist, explains that inflammation and changes in the microbiome can cause the brain's immune cells, known as microglia, to adopt a damaging, inflammatory mode. When microglia enter this state, the risk for neurodegenerative diseases such as Alzheimer’s and Parkinson’s, along with other forms of cognitive decline, is elevated. Previous research has also linked artificially sweetened beverages to higher risks of dementia and stroke, with another substitute, sucralose (not included in this study), being associated with poorer memory and executive functioning, according to Thomas Holland, MD.

The study also highlighted a particularly strong link for individuals with diabetes. People under 60 with diabetes who consumed more artificial sweeteners faced even greater risks of cognitive decline and early brain aging. Dr. Suemoto noted that diabetics frequently use artificial sweeteners as a sugar substitute. Dr. Perlmutter further explained that diabetes already imposes stress on metabolism and the microbiome, creating a pre-existing inflammatory state. Adding artificial sweeteners appears to intensify this inflammation, further stimulating microglia to cause damage in the brain.

Given the emerging evidence, experts advise caution regarding sugar substitutes. While more research is necessary, Dr. Suemoto recommends reducing consumption when possible. However, this recommendation does not endorse swapping artificial sweeteners for added sugar, as numerous studies have linked high sugar intake to dementia and various other health problems. The ideal approach, as suggested by Dr. Perlmutter, is to gradually retrain tastebuds to prefer less sweet foods. The overarching goal should be to reduce overall sweetness, consume fewer processed foods, and increase intake of fiber-rich whole foods to support both gut and brain health. If a substitute is deemed necessary, less-processed options like stevia or tagatose are recommended.