Low- and zero-calorie sweeteners include synthetically made chemicals like aspartame and sucralose, as well as natural extracts like stevia and monkfruit.The Associated Press
Over the past two decades, the consumption of low- and zero-calorie sweeteners has increased worldwide, a trend driven by health concerns over added sugars and a global shift toward an increasingly ultraprocessed diet.
Yet, growing evidence suggests such sweeteners are not as benign as once thought.
Observational studies have tied a long-term higher intake of them to an elevated risk of Type 2 diabetes, cardiovascular disease, cancer and depression.
Now, new research supports the findings that low- and zero-calorie sweeteners pose health risks, this time involving the brain.
Another reason to cut back on low-calorie sweeteners
The findings suggest that consuming lots of these sweeteners can quicken the rate of cognitive decline in middle age.
Here’s what to know about the research, plus how low- and zero-calorie sweeteners may impair memory and thinking skills.
What are low- and zero-calorie sweeteners?
Also called non-sugar substitutes, low- and zero-calorie sweeteners include synthetically made chemicals (for example, aspartame, sucralose, acesulfame potassium, saccharin, cyclamates), as well as natural extracts (such as stevia, monkfruit, sugar alcohols, tagatose), which may or may not be chemically modified.
The main food sources for many of these sweeteners are ultraprocessed foods such as diet soft drinks, diet flavoured yogurt and no-sugar-added condiments, baked goods, candies, chewing gum, frozen desserts and protein bars.
Some may also be sold as tabletop sweeteners, especially sucralose and aspartame.
Diet soft drinks are one of the main sources of these sweeteners.Reuters
About the latest research
The study, published Sept. 3 in the journal Neurology, analyzed data from 12,772 adults in Brazil enrolled in the Brazilian Longitudinal Study of Adult Health, which is investigating the development and progression of chronic disease.
Participants were between the ages of 35 and 74 and free of dementia at the beginning of the study. They completed a detailed questionnaire about their usual food and drink consumption over the previous 12 months.
This information was used to calculate each participant’s intake of seven common sweeteners: aspartame, saccharin, acesulfame potassium, erythritol, sorbitol, xylitol and tagatose.
Participants, who were followed for an average of eight years, also underwent cognitive tests to evaluate memory, language skills, brain processing speed and executive function (mental skills used in planning and problem-solving). Global (overall) cognition was also scored.
Combined and individual non-sugar substitutes tied to faster brain aging
Over all, participants who had the highest total intake of low- and zero-calorie sweeteners had a significantly greater decline in cognition and memory compared with those whose diets contained the least.
Participants who consumed the most low- and zero-calorie sweeteners (191 milligrams a day on average) – versus the least (20 mg a day on average) – experienced a 63-per-cent faster rate of cognitive decline over eight years, equivalent to 1.6 years of cognitive aging.
For perspective, 191 mg of these sweeteners is equivalent to the amount found in 16 packets of Splenda or nearly 16 ounces (461 millilitres) of diet cola.
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People in the middle tier for sweetener intake (66 mg a day on average) had a 35-per-cent faster rate of cognitive decline compared with participants in the lowest tier, equivalent to 1.3 years of cognitive aging.
Except for tagatose, higher intakes of each individual sweetener were also associated with accelerated cognitive decline. Tagatose, approved in Canada in 2022, is a low-calorie sweetener that’s produced commercially from the milk sugar lactose.
These findings were most pronounced among participants with diabetes.
When the researchers looked at the results by age, they found that only people under 60 who had the highest intake of sweeteners had faster rates of cognitive loss. This trend wasn’t observed in participants over 60.
This finding suggests that middle-aged adults should be cautious about consuming low- and zero-calorie sweeteners.
Middle age has been identified as a critical period for brain health in later life. In midlife, cognitive function as well as brain structure and function start to decline.
Strengths, limitations
The study is credited for its large and diverse sample size and its inclusion of younger participants. Most studies of cognitive aging have focused on older adults.
A limitation was that dietary intake was assessed only at the start of the study. As a result, longer-term diet changes that could have influenced the results weren’t captured.
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The findings don’t prove that these sweeteners directly caused cognitive decline. This observational study reported associations only.
How non-sugar substitutes may harm the brain
While the exact mechanism isn’t clear, inflammation and microbiome changes are believed to be involved.
When low- and zero-calorie sweeteners are broken down in the body, it’s possible they produce toxic metabolites that inflame brain cells and weaken the integrity of the blood-brain barrier, as has been demonstrated in rodents.
Artificial sweeteners have also been shown to disrupt the gut microbiome – in mice and humans – in a direction that causes inflammation and glucose intolerance.
Should you skip sweeteners?
While more research is needed, the evidence we have so far should give us pause.
If low- and zero-calorie sweeteners are part of your daily diet, I recommend you cut back or eliminate them completely.
If you consume these sweeteners only occasionally, you don’t need to panic. There’s no evidence that doing so is harmful.
Leslie Beck, a Toronto-based private-practice dietitian, is director of food and nutrition at Medcan. Follow her on X @LeslieBeckRD
