Sweeteners are often marketed as “better than sugar”, but is that really true? Arguably not according to a study out of Brazil that suggests consuming high levels of artificial sweeteners, found in diet fizzy drinks and processed snacks, accelerated declines in memory and thinking skills, says James Witts.
The effect was so stark, said the researchers, that it was the equivalent of around an extra 1.6 years of brain ageing with the greatest hit on those under 60 and those who had diabetes.
The study included 12,772 adults from across Brazil whose average age came in at 52 years old. Each was followed for eight years. At the start of the study, every participant completed a dietary questionnaire, broadly detailing what they’d eaten and drunk over the past year. The researchers then split the subjects into three groups based on the total amount of artificial sweeteners they consumed.
These included aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol and tagatose. Many of those will be familiar to you, as they’re found in ultra-processed foods like squash, energy drinks and low-calorie desserts, while some are simply used as standalone products.
Cognitive assessments were conducted at the beginning, middle and end of the study to monitor changes in memory, language and thinking abilities. These evaluations measured skills such as verbal fluency, working memory, word recall and processing speed.
What did the researchers find? That those who consumed the highest amount of sweeteners – equivalent of 191mg a day, which for aspartame is the equivalent of one can of pop – exhibited a 62% more rapid drop in overall thinking and memory skills than the lowest group, who consumed an average 20mg each day. The middle group suffered a decline 35% faster than the lowest group or around 1.3 years of ageing.
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They also discovered that those under 60 who recorded high levels of sweeteners showed a significant mental decline compared to their contemporaries, which wasn’t find in the subjects who were over 60. The link was also stronger in those with diabetes, which perhaps wasn’t surprising as those with diabetes were naturally in the higher group because this group commonly replaces sugar for sweeteners.
"Low- and no-calorie sweeteners are often seen as a healthy alternative to sugar,” said study author Claudia Kimie Suemoto of the University of São Paulo in Brazil. “However, our findings suggest certain sweeteners may have negative effects on brain health over time.”
The authors referenced further studies when citing possible causes, including sweeteners impairing glucose metabolism, which is important for brain energy use and is known to harm cognitive function. Inflammation and gut microbiome changes were further ideas mooted.
The team suggest further research is needed to confirm, or disprove, their findings. They also suggest it’s relevant to investigate whether other refined sugar alternatives, such as honey, maple syrup and coconut sugar would be effective, healthy replacements.
It’s the latest research to raise concerns about the possible health risks of artificial and no-sugar sweeteners. A 2022 study in the British Medical Journal tracked artificial sweetener intake over time of 103,388 subjects and discovered that a higher intake was associated with a 9% increased risk of cardiovascular disease, while 2024 research found a “significant association” between high consumption of artificially sweetened beverages and increased incidence of strokes.
All in all, for calorie control sweeteners are generally better than sugar. But the picture is far less clear when it comes to the long-term impact on health. The ideal is to reduce intake of both and lean more heavily naturally unsweetened drinks and foods.
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