Artificial sweeteners are often marketed as the smart choice for weight management and diabetes control. But new research suggests some of these sugar substitutes may come with a hidden cost: a faster decline in memory and thinking skills, equal to more than a year of extra brain ageing.
The study, published in Neurology, the journal of the American Academy of Neurology, tracked the diets and cognitive health of 12,772 adults in Brazil, with an average age of 52. Participants were followed for around eight years.
Researchers focused on seven widely used artificial sweeteners:
- Aspartame
- Saccharin
- Acesulfame-K
- Erythritol
- Sorbitol
- Xylitol
- Tagatose
These ingredients are commonly found in diet sodas, flavoured waters, energy drinks, yoghurts, sugar-free chewing gum, and low-calorie desserts. Some are also sold as tabletop sweeteners.
Faster brain ageing
Participants were divided into three groups based on how much of these sweeteners they consumed.
- The lowest group averaged 20 mg per day – roughly the amount found in half a stick of sugar-free gum.
- The highest group consumed an average of 191 mg per day – equal to about one can of diet soda.
When researchers tested memory, language, and processing speed at several points during the study, they found that people in the highest-consumption group experienced a 62% faster decline in thinking skills, equivalent to 1.6 years of additional brain ageing. Those in the middle group also showed faster decline – about 35% faster than the lowest group, equal to 1.3 years of ageing.
The link was strongest in people under the age of 60. In this group, higher intake of sweeteners was tied to a more rapid decline in verbal fluency and overall cognition. Surprisingly, the same effect was not seen in people over 60.
For people living with diabetes, the association appeared even stronger. Researchers noted that many with diabetes regularly turn to sugar-free products, which may unintentionally expose them to higher amounts of these additives.
Not all sweeteners are equal
When each sweetener was studied separately, six of them – aspartame, saccharin, acesulfame-K, erythritol, sorbitol, and xylitol – were linked with cognitive decline, particularly in memory performance. Only tagatose showed no connection to brain ageing.
Dr. Claudia Kimie Suemoto of the University of São Paulo, one of the study authors, noted:
“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.”
What the study cannot prove
Researchers highlighted several limitations. The data on diet came from food questionnaires, which depend on participants’ memory and honesty. Not all types of sweeteners were included, meaning some commonly used ones remain unstudied.
Importantly, the study shows a link – but does not prove that artificial sweeteners directly cause cognitive decline.
Still, the findings add to growing concerns about the long-term health effects of ultra-processed foods and sugar alternatives. More research will be needed to confirm these results and explore whether natural substitutes such as honey, maple syrup, applesauce, or coconut sugar could be safer choices.
Artificial sweeteners are everywhere, from coffee shops to supermarket shelves, and millions of people use them daily, believing they are a healthier alternative to sugar. This study suggests the story may be more complicated, especially for younger adults and those with diabetes.
08.09.2025.
