Aspartame could be bad for your brain and heart

In this Article (Index)

• Aspartame: the sweetener
• Aspartame's Maximum Daily Allowance
• Aspartame: Cognitive and Cardiac Side Effects
• Lowers appetite and Body Fat
• Negative effects to the heart
• Brain: Cognitive Impairement

Aspartame: the sweetener

What is it?

Aspartame is an artificial food sweetener, synthesized from two aminoacides, aspartic acid and L-phenylalanine, which are reacted in a process involving acetic acid and a palladium catalyst. The final product is a chemical known as L-aspartyl-L-phenylalanine methyl ester. The image above shows its molecular formula.

Apartame was a chance discovery that happened sixty-years ago, when James M. Schlatter, seeking a drug to prevent ulcers, stumbled apon this product which is nearly 200 times sweeter than sugar (sucrose).

It has almost zero calories which makes it an ideal artificial sweetener. However, since it is unstable when heated, losing its sweetening properties, it is only used in products that are not baked such as sodas, powdered fruit juices, gelatin, yougurt, sugar-free syrups, chewing gum, etc.

Some brand names for Aspartame are Nutrasweet®, Equal®, Canderel®, and Sugar Twin®

As it contains phenylalanine it should be labeled as not suitalbe for people with phenylketonuria (PKU), a genetic disorder that causes difficulty in metabolizing phenylalanine.

Maximum Daily Allowance

The limits set in the European Union by the European Safety Authority (EFSA) are 40 milligrams per kilogram of body weight (mg/kg). In America, the U.S. Food and Drug Administration (FDA) has set a slightly higher value, which is 50 mg/kg. The World Health Organization set the dose at 40 mg/kg.

Doses below the Maximum Recommended Dose can be harmful

The study that we mention further down administered doses well below the Maximum Daily Allowance, and even so, found harmful effects.

Aspartame: Cognitive and Cardiac Side Effects

The paper noted the wide use of aspartame as a sweetener to replace sugar and reduce its intake. It is consumed by those trying to manage their weight. The authors wanted to investigate the long term effects of an intermittent intake of aspartame at levels below the maximum allowed doses recommended by health authorities.

The paper found that aspartame decreased appetite and also body weight "owing principally to a 20 % reduction in fat deposits." It also found that it caused a mild enlargement of the heart (mild cardiac hypertrophy) and altered the memory and cognitive abilities of the mice that consumed it.

Since most studies have been short-term, they implemented a 52-week long-term study and administered a "human equivalent dose (HED) averaging 7 mg/kg body weight per day, well below recommended maximum of 50 mg/kg/day."

It compared mice consuming this dose of aspartame in an intermittent manner (3 days every 2 weeks) and compared them with a control group. The study was designed to mimic human consumptio patterns.

...the study demonstrates that long-term exposure to artificial sweeteners can have a detrimental impact on organ function even at low doses, which suggests that current consumption guidelines should be critically re-examined. Irati Aiestaran-Zelaia, et al. (2025)(1)

Weight Loss: Less appetite and lower body fat

At least in this study (there have been different outcomes in different studies regarding the weight loss effect of aspartame in mice), "the findings strongly suggest that aspartame depresses appetite and reduces body fat in adult mice." It led to a significant 20% drop in body fat.

Negative effects to the heart

The wall that separates the left and right sides of the heart, known as septal wall, was flattened in aspartame-treated mice, which experienced a 25% decrease in septal curvature. They also experienced a 45% increase in the blood retained in their right ventricle after their hearts contracted meaning that less oxygen-poor blood gets pumped to the lungs to replenish oxygen levels. The output of both Left and Right ventricles was reduced by 26% and 20%, respectively (the left ventricle pumps the oxygenated blood to the entire body).

This retention could be the reason the septum is flattened, and as the authors state: "chronic aspartame-induced cardiac stress... further suggesting impaired cardiac function as a result of chronic aspartame exposure... Thus, aspartame appears to induce structural changes in the heart and to impair its performance."

The analysis at the end of the trial revealed mild hypertrophy (enlargement) along with fibrosis (scarring) and the presence of pro-inflammatory cells, which can cause damage to the heart.

Brain: Cognitive Impairement

The study reported that "Aspartame alters glucose uptake in the brain and may impair cognitive function." It noticed that initially, aspartame increased the brain's demand of glucose by a factor of two, glucose is an important source of energy for the brain. However, after 10 months, the mice who were not consuming aspartame overtook those on the intermittent-aspartame diet: "glucose uptake was higher in the control mice, reaching approximately ∼ 1.5-times more than in the aspartame-treated animals." This variation in the uptake of glucose could have a negative impact on the brain's normal functioning.

The mice were subjected to the classic Barnes Maze test, where their cognitive abilities were assessed, "Aspartame treated mice display behavior suggestive of reduced spatial learning and memory capacity."