Many of us reach for sugar substitutes in a bid to cut calories and protect our health—but new research suggests that this sweet swap could come at a hidden cost to our brains.
A recent study published in Neurology found that adults who consumed the highest amounts of certain low- and no-calorie sweeteners experienced faster declines in memory and thinking skills than those who consumed the least. The link was even stronger in people with diabetes.
The sweeteners studied included aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose, common in many consumer products.
“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,” said study author Claudia Kimie Suemoto, MD, PhD, of the University of São Paulo in Brazil.
The study followed 12,772 adults across Brazil, with an average age of 52, for around eight years. Participants reported their diets over the previous year and were divided into three groups based on sweetener intake—from 20 milligrams per day in the lowest group to 191 mg/day in the highest.
Cognitive tests tracking memory, language, and thinking skills were conducted throughout the study. After adjusting for factors like age, sex, high blood pressure, and heart disease, researchers found that the highest sweetener consumers experienced a 62 per cent faster decline in overall thinking and memory skills—roughly equivalent to 1.6 years of ageing. Even the middle group declined 35 per cent faster, or about 1.3 years of ageing.
“More research is needed to confirm our findings and to investigate if other refined sugar alternatives, such as applesauce, honey, maple syrup or coconut sugar, may be effective alternatives,” Suemoto said.
For anyone relying on sugar substitutes to stay healthy, these findings offer a cautionary tale: moderation may be key, and there’s no substitute for keeping both diet and brain health in check.
Just as sugar substitutes may influence brain health, other everyday dietary choices could also play a surprising role in cognitive function—even something as simple as your morning breakfast.
As part of the study, published in the General Psychiatry journal, researchers from Anhui Medical University in Hefei, China, explored data from the China Health and Nutrition Survey, involving around 3,000 adults with an average age of 63. Participants were asked to share details about their diets and underwent cognitive function tests, including tasks like recalling words and challenges involving number patterns.
Upon a follow-up about five years later, the researchers discovered a link between thiamine consumption and a drop in cognitive test scores. While both too little and too much thiamine can be harmful, the researchers identified an ideal thiamine amount, emphasising the importance of balance.
“We speculate that high levels of dietary thiamine intake may lead to cognitive decline by inducing elevated levels of acetylcholine in the brain,” the research team said.
The study suggests that an excess of dietary thiamine might lead to cognitive decline by triggering elevated levels of acetylcholine in the brain. On average, participants were consuming 0.93 mg per day, with the researchers identifying 0.68 mg per day as the sweet spot. The range between 0.6 mg and 1.00 mg per day showed minimal risks.
Together, these studies highlight an important message: even seemingly small choices—whether it’s using a sugar substitute or how much vitamin you get at breakfast—can influence long-term brain health. Moderation, balance, and mindful eating remain key to protecting both body and mind.
IMPORTANT LEGAL INFO This article is of a general nature and FYI only, because it doesn’t take into account your personal health requirements or existing medical conditions. That means it’s not personalised health advice and shouldn’t be relied upon as if it is. Before making a health-related decision, you should work out if the info is appropriate for your situation and get professional medical advice.
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