New Study Reveals Long-Term Risks of Aspartame on Brain and Heart

Research conducted by a team led by Spain’s CIC biomaGUNE and the Biogipuzkoa Health Research Institute has revealed concerning long-term health effects associated with the artificial sweetener aspartame. This study, the first of its kind to reflect real-world conditions, identifies detrimental impacts on brain and heart function that resonate with findings from previous short-term studies.

The year-long investigation involved administering aspartame to mice at a dosage significantly below the current Acceptable Daily Intake (ADI) guidelines. This approach aimed to address two significant limitations in existing research: the brief duration of studies and the use of unrealistically high dosages. Although aspartame is one of the most scrutinized food additives, shorter studies often fail to capture long-term effects, which has allowed organizations such as the World Health Organization (WHO) to classify it as “possibly carcinogenic to humans” while the US Food and Drug Administration (FDA) maintains its safety below the ADI threshold.

During the experiment, the research team exposed 18 mice to 7 mg/kg of body weight—equivalent to approximately one-sixth of the maximum recommended daily intake—three days every two weeks. This was compared with a control group of 14 mice that received no aspartame. The researchers aimed to determine how aspartame affected heart and brain function, as well as fat levels and body weight, while comparing these effects to other sugars and sweeteners.

Brain Function and Metabolism Impacted by Aspartame

Over the course of the study, significant changes were observed in brain energy processing. Using FDG-PET imaging, researchers tracked glucose uptake across the entire brain and specific regions. After just two months of intermittent aspartame intake, glucose uptake in the brains of the treated mice doubled compared to the control group. However, by the six-month mark, this initial spike reversed. At ten months, the aspartame-fed mice were utilizing approximately 50% less glucose than their counterparts, indicating a troubling decline in energy metabolism.

This decline is critical, as the brain relies almost exclusively on glucose for essential functions, including neuron firing and memory maintenance. The study highlights how prolonged aspartame consumption may shift brain activity from an early stage of heightened energy use to a chronic state of underutilization, which is often linked to metabolic stress.

Biochemical analysis using magnetic resonance spectroscopy further illuminated these changes. After two months, levels of N-acetylaspartate (NAA), a marker for neuronal health, were approximately 13% higher in the aspartame group. By four months, however, these benefits dissipated, and lactate levels surged to 2.5 times higher than in the control group, suggesting a deterioration in cellular function.

The relationship between astrocytes—cells that help convert glucose to lactate—and neurons is crucial in understanding these findings. When high lactate levels accumulate, neurons struggle to utilize this fuel efficiently, disrupting the brain’s energy balance. This imbalance can push the brain into “emergency mode,” leading to decreased efficiency in neural circuits, which may impair learning and attention.

Cardiac Function and Overall Health Effects

The impact of aspartame was not limited to the brain. Cardiac imaging revealed significant alterations in heart structure and function by the end of the study. The hearts of the treated mice exhibited reduced pumping efficiency, with chambers emptying less completely and delivering less blood with each heartbeat, despite minimal structural damage. Over time, this could lead to insufficient blood and oxygen reaching vital organs, including the brain.

Interestingly, while aspartame-treated mice showed about 20% less total body fat than the control group over the 12 months, this reduction did not correlate with improved metabolic health. Although their body weights were similar, the fat distribution shifted, resulting in a larger proportion of visceral fat around organs and less lean mass. This type of fat distribution can impose additional strain on the heart and metabolic processes, helping to clarify why the reduction in fat mass coincided with changes in cardiac and brain energy use.

The researchers concluded that while aspartame appears to reduce fat deposits in mice, it does so at the expense of heart health and cognitive performance. They noted, “Although this sweetener may help achieve weight loss in mice, it is accompanied by pathophysiological changes in the heart and, possibly, in the brain.”

While the findings are significant, they are based on an animal model, and direct implications for human health remain to be established. Nonetheless, the study, published in the journal Biomedicine & Pharmacotherapy, underscores the urgent need for long-term research to fully understand the chronic effects of aspartame consumption on brain and heart metabolism.

Since its approval by the FDA in 1974, aspartame has become one of the leading artificial sweeteners in the marketplace, with previous studies indicating potential health risks, including serious cardiovascular issues and cognitive impairments. The new evidence adds to ongoing discussions about the safety and long-term consumption of this widely used additive.