In mice, small doses of aspartame taken over a long period alter brain metabolism and heart function.
Research conducted on mice evaluated the effects of aspartame consumption for the first time, filling two gaps in previous studies: that is, it observed the consequences of long-term intake of the natural sweetener, and not just immediate intake as has happened so far; and he did it by administering non-excessive quantities of aspartame to the rodents, for once close to those consumed by humans in real life.
The results of the study, published in the scientific journal Biomedicine & Pharmacotherapydeliver a negative verdict on the effects of aspartame on health: if it is true that it contributes to weight loss, it however seems to interfere with the metabolism of the brain and with the structure and functionality of the heart.
Moderate, intermittent and prolonged consumption
In 2023, aspartame, an artificial sweetener used in many food products, including diet foods and drinks, was classified as “possibly carcinogenic to humans” by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) and by the Joint Committee of Experts on Food Additives (JECFA) of the Food and Agriculture Organization of the United Nations (FAO), with the clarification, however, that for a It is still safe for a person to consume it in quantities lower than the acceptable daily intake (ADI), which is up to 40 mg per kg of body weight.
As we explained then when bringing you the news (to learn more), this is a threshold that is difficult to overcome.
Scientists from the Centro de Investigación Cooperativa en Biomateriales CIC biomaGUNE and the Biogipuzkoa Health Research Institute (Spain) subjected 18 mice to a significantly lower dose of aspartame, approximately one sixth of the maximum acceptable dose, for one year. The rodents consumed aspartame for three days every two weeks, while a control group of 14 mice consumed none.
The effects of aspartame on the brain
The scientists used a type of brain imaging test (PET) to evaluate the brain’s uptake of glucose (the “fuel” of neurons) and observed a strange pattern in the way the brains of mice fed aspartame consumed energy. After two months, the neurons of these mice seemed to require twice as much glucose as those of the control group, but around six months the situation was reversed, and by ten months of intake, the brains of the aspartame-fed mice were burning half as much glucose as those of the control group.
Aspartame caused the mice’s brains to shift from a phase of increased energy use to a more chronic phase of glucose underuse, a symptom of metabolic stress.
In effect, it had robbed the mice’s brains of their main energy source.
The brain in emergency mode
The observation was confirmed by the analysis of metabolic products present in the brain. Astrocytes, the star-shaped cells that support neurons in the brain, know how to turn glucose into lactate, a fuel that neurons use more easily and which appears to play an important role in the formation of memories.
If lactate levels remain consistently high, neurons cannot use it efficiently and the substance builds up, interfering with the brain’s energy metabolism. After 8 months of taking aspartame, lactate levels in the brains of the mice were 2.5 times higher than those of the control group.
The brains of these mice appeared to be constantly in emergency mode, less efficient at attention, navigation, memory recall and problem-solving tasks.
The impact on the heart
At the end of the study, the hearts of mice treated with aspartame appeared less efficient at pumping blood: the cardiac chambers, that is, the internal compartments of the heart, which receive blood and pump it out, filled less completely and returned less blood per beat. This means that the animals’ organs, including the brain, received less oxygenated blood.
Less fat, but in the wrong place
To be sure, mice that took aspartame stored 20 percent less fat than control mice over the course of a year. But the (minor) accumulated fat has been redistributed in an unhealthy way, concentrating around the organs (visceral fat), a conformation that normally strains the heart and metabolism. This is why, the researchers concluded, “although this sweetener can help mice lose weight, it is accompanied by pathophysiological changes in the heart and, probably, the brain.” Of course, what is described is the result of a study on an animal model: it remains to be seen whether similar effects also occur in humans.
