That soda you’re drinking may be short on calories, but it could put a big dent on your brain health.
Consuming low- and no-calorie sweeteners like those found in many diet and zero sugar sodas can speed up cognitive decline and cause long-term harm to cognitive function, according to results of an eight-year study published Sept. 3 in the journal Neurology.
The number of people with dementia worldwide is expected to grow considerably in the coming decades, up from 50 million in 2019 to 152 million in 2050, writes lead author Natalia Gomes Gonçalves, PhD, of the University of São Paulo in Brazil, and colleagues. The number of people who have dementia and live in low- and middle-income countries also is expected to increase from 60 percent to 68 percent by 2050, the researchers note.
“A healthy lifestyle has been linked to a decreased risk of cognitive decline and dementia,” they say. “On the other hand, high consumption of ultra-processed foods has been linked to accelerated cognitive decline and increased risk of dementia.”
Sugar-free ultraprocessed foods typically contain low- and no-caloric sweeteners such as aspartame, acesulfame-k, saccharin, and sugar alcohols. Many of these foods can be found in the average person’s pantry, from diet and milk-based beverages to yogurt to low-calorie desserts. People are ingesting these sweeteners more and more, too—consumption of many of them rose worldwide from 2008 to 2017—even though they have been linked to an increased risk of type 2 diabetes, cancer, cardiovascular disease, and depression, the study notes.
Still, researchers remained uncertain about a possible connection between the sweeteners and cognitive decline, so they turned to the Brazilian Longitudinal Study of Adult Health, which had enrolled active and retired civil servants from six cities in that country. The researchers focused on 12,772 people 35 or older. Participants had an average age of 51.9 years; 54.8 percent were women, and 43.2 percent were Black or mixed race.
The researchers evaluated the participants’ cognition every four years in three time periods from 2008 to 2019. The tests checked the participants’ memory, language, and executive function (skills people use to handle everyday tasks). Participants also completed a food frequency questionnaire, which researchers used to determine how much of seven low- and no-calorie sweeteners—aspartame, saccharin, acesulfame k, erythritol, xylitol, sorbitol, and tagatose—they had consumed.
On average, the researchers found, participants consumed 92.1 mg of low- and no-calorie sweeteners per day. Sorbitol—a sugar alcohol also known as glucitol—was the most commonly used sweetener, with 63.8 mg consumed on average per day, while erythritol was least common, at just 0.1 mg per day.
Over an eight-year follow-up period, participants who consumed the most low- and no-calorie sweeteners experienced a 32 percent higher rate of memory decline compared to those who consumed the least. That top group also saw higher rates of decline in global cognition (62 percent) and verbal fluency (173 percent).
The researchers dug even further, looking at the individual impact of the seven sweeteners. They found that people who consumed more aspartame, saccharin, sorbitol, and xylitol had a faster rate of decline in memory, verbal fluency, and global cognition. Consuming more acesulfame-k and erythritol, meanwhile, was associated with a higher rate of decline in just two categories, memory and global cognition. And as for tagatose? The researchers did not find any association between that and cognitive decline.
Whether participants had diabetes also appeared to play a role in how the sweeteners affected their brain health. People without diabetes who consumed more low- and no-calorie sweeteners saw their verbal fluency and global cognition decline faster, but those who did have diabetes saw their memory and global cognition decline more quickly. In people with diabetes, the magnitude of the association between the sweeteners and cognitive decline was stronger than in those without diabetes.
Because the study shows that these sweeteners can cause long-term harm to cognitive health, the researchers say, “opting for natural sweeteners, such as tagatose, or other sugar alternatives may help mitigate the potentially harmful association observed.”
They also point out that more studies will be needed to confirm their findings and to see “if other refined sugar alternatives, such as applesauce, honey, maple syrup, or coconut sugar may be effective alternatives to avoid the detrimental association between [the sweeteners] and cognitive function.”
