NEW YORK: Artificial sweeteners, widely used as sugar substitutes, may be linked to faster cognitive decline and signs of brain ageing, according to new research.
While the findings do not prove cause and effect, they have renewed debate over the long-term health impact of low- and no-calorie sweeteners consumed by millions of people worldwide.
A recent study published in Neurology, the medical journal of the American Academy of Neurology, found that higher consumption of several artificial sweeteners was associated with declines in memory and overall thinking skills equivalent to about 1.6 years of brain ageing.
The research has prompted caution among scientists, even as food industry bodies stress that sweeteners approved by regulators remain safe.
What did the study find?
The study analysed data from 12,772 Brazilian adults, with an average age of 52, who were followed for around eight years.
Participants, most of them civil servants, reported their food and drink intake and underwent repeated cognitive tests measuring memory, verbal fluency, language and overall thinking skills.
Researchers divided participants into three groups based on sweetener intake. Those with the highest consumption showed cognitive decline that was 62% faster than those with the lowest intake.
This decline was described as equivalent to around 1.6 years of ageing. The middle group showed a 35% faster decline, equivalent to about 1.3 years of ageing.
The association was strongest among people under the age of 60. No clear link was observed in participants aged 60 and above.
The study also found that the link between sweetener consumption and cognitive decline was stronger in people with diabetes, a group more likely to rely on sugar substitutes.
Which sweeteners were involved?
The sweeteners linked to faster cognitive decline included aspartame, saccharin, acesulfame-K, erythritol, sorbitol and xylitol.
These are commonly found in ultra-processed foods and drinks such as diet sodas, flavoured water, energy drinks, yoghurt and low-calorie desserts.
No association was found between tagatose, a natural sugar alternative, and cognitive decline.
For context, the highest average intake of aspartame recorded in the study was equivalent to about one can of diet soda per day.
Expert perspective
Claudia Kimie Suemoto, the study’s senior author and an assistant professor of geriatrics at the University of São Paulo Medical School, said the findings raise concerns but should be interpreted carefully.
“Low- and no-calorie sweeteners are often seen as a healthy alternative to sugar,” Suemoto said. “However, our findings suggest certain sweeteners may have negative effects on brain health over time.”
Suemoto, who is also an epidemiologist specialising in dementia and brain ageing, stressed that more research is needed to confirm the results and to explore safer alternatives.
The study was observational, meaning it could identify associations but not prove that sweeteners directly cause cognitive decline. Researchers also noted limitations, including reliance on participants’ self-reported diets.
Response of regulators and industry
Several artificial sweeteners, including aspartame and saccharin, are approved by the US Food and Drug Administration and other global health authorities as safe for consumption.
Industry groups questioned the conclusions of the study. The British Soft Drinks Association said the research could not demonstrate causation and noted that non-sugar sweeteners have been used safely for decades.
The International Sweeteners Association also said there is an established scientific consensus on sweetener safety, describing the study as insufficient to prove direct harm.
Health experts say the findings do not mean people should immediately stop using artificial sweeteners.
Instead, they highlight the need for moderation and further research, particularly for middle-aged adults and people with diabetes.
Researchers said future studies should examine whether other sugar alternatives, such as honey, maple syrup or coconut sugar, have different long-term effects on brain health.
