You may think of cognitive decline as something that happens naturally with ageing. As you get older, memory can slow, brain fog can increase and complex problems may feel harder to solve. But research shows reduced cognitive function is not a given and that lifestyle changes can make a difference. More specifically, there may be a link between artificial sweeteners and cognitive decline, and cutting back on these sweeteners may help sharpen your thinking.
New research linked higher levels of artificial sweetener use with a faster rate of decline in thinking and memory skills. For the study, researchers followed 12,772 adults with an average age of 52 for about eight years. The participants answered questionnaires about their diet at the start of the study, sharing what they ate and drank over the previous year.
Using that information, the researchers divided participants into three groups based on their artificial sweetener use. Those in the lowest group had an average of 20 milligrams of artificial sweetener a day, while those in the highest group had 191 milligrams daily. (That higher level is about what you would find in a can of diet soft drink.) The participants also completed cognitive tests at the beginning, middle and end of the study to track potential changes in their memory, language and thinking skills over time.
The researchers discovered that people who regularly had higher amounts of artificial sweeteners had a 62% faster decline in thinking and memory skills compared to those who had the lowest amount. That is equivalent to about 1.6 years of ageing. People in the middle group had a decline that was 35% faster than the lowest group, which the researchers said is equivalent to about 1.3 years of ageing. The team also found that people with diabetes had a faster rate of decline in memory and cognition than people without the condition.
More specifically, the study linked six artificial sweeteners to cognitive decline. They were:
- Aspartame (often found in diet drinks and some dairy products)
- Saccharin (commonly used in tabletop sweeteners)
- Acesulfame-K (used in beverages, lollies and baked goods)
- Erythritol (used in many lower-sugar or keto-style products and drinks)
- Sorbitol (often used in sweets and sugar-free products)
- Xylitol (found in chewing gum and oral care products)
The researchers wrote in the conclusion that the findings “suggest the possibility of long-term harm” on cognitive function from using artificial sweeteners and sugar alcohols.
The study raises plenty of questions about artificial sweeteners and what this means for your brain health if you use them regularly. Here is what experts want you to keep in mind.
Do artificial sweeteners cause cognitive decline?
There are a few things to keep in mind before jumping to that conclusion. This research is an observational study, so it does not prove that artificial sweeteners cause cognitive decline, it shows an association. The study also did not track factors such as activity levels, sleep or overall diet quality, which can all influence brain health, notes registered dietitian nutritionist Keri Gans.
As for why this link might exist, the picture is still emerging. “Our hypothesis is that artificial sweeteners may trigger processes such as neuro-inflammation, neuro-degeneration or disruption of the gut–brain axis based on animal models,” says Dr Claudia Kimie Suemoto. These studies suggest that aspartame can lead to inflammation in the brain, while sugar alcohols like erythritol and sorbitol may alter the gut microbiota and compromise the blood–brain barrier, she explains.
Using these sweeteners regularly may also leave your brain without an ideal source of fuel, says neurologist Dr Clifford Segil. “These artificial sweeteners do not provide old-fashioned sugar or glucose into your body that is needed to be broken down in your body for energy and normal brain function,” Dr Segil explains. In other words, if your diet leans heavily on artificial sweeteners or sugar alcohols, your brain may not be getting the steady fuel it prefers. Over time, that could theoretically contribute to some people developing problems with memory and thinking more quickly than others.
Why is the rate of decline faster in people with diabetes?
Gans says there may be a few reasons why this link is stronger in people with diabetes. “People with diabetes may already be at a higher risk for memory and thinking changes because high blood sugar and insulin resistance can affect blood vessels and the brain,” she says. “So, if there’s any added strain, it may show up more strongly in this group.” People with diabetes may also use low-kilojoule sweeteners more often than those without the condition, which may further strengthen this association, she adds.
Dr Suemoto agrees. “People with diabetes are more likely to consume artificial sweeteners as a substitute for sugar, so their overall exposure may be higher than people without diabetes,” she says. “In addition, diabetes itself is already a strong risk factor for cognitive decline related to Alzheimer’s disease and vascular dementia, which probably makes the brain more vulnerable to harmful exposures.”
Certain sweeteners, like aspartame and acesulfame-K, may even affect the body’s ability to metabolise glucose and influence the gut microbiota, “potentially worsening metabolic control,” Dr Suemoto adds.
One more thing to consider: “In patients with diabetes whose bodies are not processing their natural sugars, the effects of artificial sweeteners may cause their brains to be ‘tricked’ into breaking down artificial sugars by mistake,” Dr Segil says. Over time, this could also have an impact on cognition, he says.
Should you avoid artificial sweeteners?
Experts are cautious about saying you must cut out artificial sweeteners completely for the sake of your brain. They do agree that easing up is a smart move. “It is wise to limit consumption as much as possible, ideally avoiding daily use,” Dr Suemoto says.
Dr Segil agrees. “Be aware that these sweeteners may not be as healthy as you think,” he says. “Fruit is the best source of natural sugars and should really be used in place of diet drinks or protein bars to be healthy.”
To support cognitive health as you age, Dr Segil suggests focusing on habits that are proven to help your brain: eat mostly whole foods, stay active and get plenty of sleep, while trying to keep artificial sweetener intake on the low side.
Still, Gans notes that the current data does not suggest you need to avoid artificial sweeteners entirely. It may simply be worth cutting back if you rely on them often. “Using sweeteners occasionally is not something most people need to worry about,” she says.
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