The impact of using sweeteners as a sugar substitute continues to be a subject of debate. They are not completely harmless, nor are they extremely harmful. Their use is regulated by the EFSA (European Food Safety Authority), which sets the limits within which their consumption is considered safe.
Nevertheless, given that the substitution has become widespread not only as a supplement but also as an ingredient in many processed products, it is monitored to ensure that abusive use does not lead to adverse effects or the development of diseases.
Some sugar substitutes may have unexpected consequences for long-term brain health, according to a recent study published in Neurology. The study examined seven low-calorie and calorie-free sweeteners and found that individuals who consumed the highest amounts experienced a faster decline in their thinking and memory skills compared to those who consumed less.
While the research showed a relationship between the use of some artificial sweeteners and cognitive decline, it did not prove they were a direct cause. Guillermo Garcia Ribas, a member of the Behavior and Dementia Study Group at the Spanish Society of Neurology (SEN), contextualizes the study. "While it opens up a new avenue of work, these are preliminary conclusions that highlight the need to determine what constitutes abuse of these substances," he emphasizes.
In this regard, Ribas states, "We are familiar with the limits of refined sugar use [maximum of 20 grams per day], but we still need to observe the effect of substitutes." According to the neurologist from the Ramón y Cajal University Hospital in Madrid, "this is a wake-up call to establish that our brain health requires a varied diet."
The artificial sweeteners examined in the study were aspartame, saccharin, acesulfame-K, erythritol, xylitol, sorbitol, and tagatose. These are mainly found in ultra-processed foods such as flavored water, sodas, energy drinks, yogurt, and low-calorie desserts. Some are also used as individual sweeteners.
"Low-calorie and calorie-free sweeteners are often perceived as a healthy alternative to sugar; however, our findings suggest that certain sweeteners may have negative effects on brain health over time," said the study's author, Claudia Kimie Suemoto, from the University of São Paulo in Brazil, in a statement.
In 2023, the World Health Organization (WHO) issued a recommendation on the use of artificial sweeteners, discouraging their use for weight loss and non-communicable diseases (diabetes, obesity, hypertension, etc), as noted by Carmen Aragón, a member of the Nutrition Area Management Committee of the Spanish Society of Endocrinology and Nutrition (SEEN). "This recommendation is based on the review of clinical trials and systematic reviews where the usual findings were the lack of long-term maintenance of weight loss and a higher risk of type 2 diabetes, cardiovascular disease, and mortality," explains the endocrinologist.
Regarding the main conclusions drawn from the study, the author points out that "while we found links to cognitive decline in middle-aged individuals with or without diabetes, those with this condition are more likely to use artificial sweeteners as sugar substitutes." Experts found a more pronounced relationship in individuals under 60, but not in those over 60.
At the same time, Suemoto also highlights the limitations observed in the current study that need further exploration. "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, can be effective alternatives," she notes.
Another limitation of the study was that not all artificial sweeteners were included. Additionally, the researchers state that the dietary information was self-reported by the participants, who may not have accurately remembered everything they ate. "Self-reporting has many gaps," says the SEN spokesperson.
In addition to these considerations, Ribas adds others that would not allow for an alert about a problem with sweeteners on brain health, beyond the necessary "wake-up call." "The consumption ranges [low, medium, and high] do not allow for a direct link or the delimitation of damages to specific quantities," he argues. The neurologist highlights that in the highest intake group, it ranges "from 120 mg to 1,200," which is too "broad" of a range not to be explored more deeply.
Therefore, the SEEN spokesperson insists that "following the WHO recommendations, it is advised to consume foods without added sugars or sweeteners in favor of naturally sweet foods like fruits."
How Was the Link Between Sweeteners and Brain Health Discovered?
The study included 12,772 Brazilian adults with an average age of 52 years who were followed for about eight years. To assess their intake, volunteers completed diet questionnaires at the beginning of the study, detailing what they ate and drank over the previous year.
The researchers divided them into three groups based on the total amount of artificial sweeteners consumed. The lowest group consumed an average of 20 milligrams per day (mg/day), and the highest group consumed an average of 191 mg/day. For aspartame, this amount is equivalent to a can of diet soda. Sorbitol had the highest consumption, with an average of 64 mg/day.
Participants underwent cognitive tests at the beginning, halfway, and end of the study to evaluate memory, language, and thinking skills over time. The exams assessed areas such as verbal fluency, working memory, word recall, and processing speed.
After adjusting for factors such as age, sex, high blood pressure, and cardiovascular diseases, the researchers found that people who consumed the highest amount of sweeteners showed a faster decline in their overall thinking and memory skills than those with lower intake, with a decline that was 62% faster. This equates to almost 1.6 years of aging, according to the authors. In the intermediate group, the decline was 35% faster than the lowest group, equivalent to approximately 1.3 years.
When the research breaks down the results by age, it finds a nuance that the researchers highlight: individuals under 60 who consumed the highest amounts of sweeteners showed a faster decline in verbal fluency and overall cognition compared to those who consumed lower amounts. However, this was not observed in individuals over 60. They also found that the relationship with faster cognitive decline was stronger in participants with diabetes than in those without the disease.
When analyzing individual sweeteners, the consumption of aspartame, saccharin, acesulfame-K, erythritol, sorbitol, and xylitol was associated with a faster decline in overall cognition, particularly in memory. However, no relationship was found between tagatose consumption and cognitive decline.