Experts contest new research linking aspartame-high diets to heart health risks

A new study indicates that aspartame might impact vascular health. Scientists reveal that the artificial sweetener increased insulin levels in mice, which contributes to atherosclerosis — a buildup of fatty plaque in arteries. This condition can lead to higher inflammation levels and may increase the risk of heart attacks and strokes.

However, critics of the study counter that the findings have yet to be repeated in humans. Moreover, they argue that the study did not prove that aspartame increases heart health risk. 

“This study has revealed much more about the known potential risks of artificial sweeteners,” comments James Leiper, director of research at the British Heart Foundation, who was not connected to the study.  

“In these mice, a diet that included an artificially high level of aspartame did exacerbate the size and number of fatty plaques in their arteries. The effect of these plaques was not measured here, but they are known to increase the risk of a heart attack or stroke greatly.”

He adds that the research findings highlight the importance of further studies to determine whether adding aspartame to food and beverages and its effect on insulin levels contributes to an increased risk of cardiovascular events. 

Although Leiper says people likely consume more artificial sweeteners than they realize, the study is not a “green light” to have more sugar instead. 

“We all need to reduce our intake of processed foods and beverages with high levels of fat, sugars, sweeteners, and salt. This is the best way of ensuring a healthy diet and a lowered risk of heart and circulatory disease.”

Sweet diet

For the study published in Cell Metabolism, researchers fed mice daily food doses with 0.15% aspartame for 12 weeks, which they say corresponds to humans consuming three cans of diet soda per day. Mice on this diet developed more extensive and more fatty plaques in their arteries and had higher inflammation levels than those without a sweetener-infused diet. 

In addition, these mice had a surge in blood insulin levels after aspartame consumption. The researchers note that the ingredient, 200 times sweeter than aspartame, “tricked” sweetness-detecting receptors in the mouth, intestines, and other tissues into releasing more insulin. 

Mice fed a high-aspartame diet had increased insulin levels and more fatty plaque buildup in arteries.They also revealed that these elevated insulin levels fueled the growth of fatty plaques in mice arteries. The team identified an immune signal called CX3CL1 that is especially active under insulin stimulation. 

“Because blood flow through the artery is strong and robust, most chemicals would be quickly washed away as the heart pumps,” says senior author Yihai Cao from the Karolinska Institute, Sweden. “Surprisingly, not CX3CL1. It stays glued to the surface of the inner lining of blood vessels. There, it acts like a bait, catching immune cells as they pass by.”

The researchers explain that such trapped immune cells are known to increase blood vessel inflammation. 

Cao says the study’s results indicate CX3CL1’s role in aspartame’s impact on the arteries. When the team removed these receptors from one of the immune cells in aspartame-fed mice, the plaque buildup did not occur. 

Study design flaws

However, researchers not involved in the study raise several concerns about its findings. Oliver Jones, professor of Chemistry at RMIT University in Melbourne, Australia, says: “I don’t think this study itself gives us more reason to worry about diet drinks or aspartame.”

“The authors would appear to think little work has been done on safety testing in aspartame; this is just not true. All food ingredients are rigorously tested and safety assessed before being approved. Aspartame is one of the most researched ingredients in the world. It is just that a lot of the data is in safety assessments for regulatory approval, not the academic literature.”

However, the scientists used mice prone to heart disease and also fed it a high-fat and high-cholesterol diet.The professor’s main concern with the study is that its authors used a particular type of lab mouse, an ApoE mouse, which is bred to be prone to heart disease. 

“They also fed it a high-fat, high-cholesterol diet, which itself increases the risk of heart disease,” which the study’s authors agree “diminishes clinical relevance.”  

Jones continues: “They also don’t seem to have measured how much of the aspartame water the mice drank, or the aspartame level in the blood, so it is unknown what the mice actually received.”

He also contests the authors’ claims that aspartame stimulates glucose or insulin levels, explaining that the ingredient consists of two common amino acids (aspartic acid and phenylalanine) joined together, which are separated in the gut. “There is no reason to think amino acids from aspartame would be worse than those from any other source.”

However, a clinical trial comparing salivary insulin levels after consuming a regular soft drink or a beverage sweetened with artificial sweeteners revealed that both drinks increased insulin levels in saliva. 

Jones maintains that even if aspartame causes some increase in cardiovascular risk, which he says the study does not prove, “that risk would likely be minimal compared to things like high fat/high sugar diets and lack of exercise.” 

Researchers urge consumers to reduce processed food and beverages intake with high levels of fat, sugars, sweeteners, and salt.Aspartame efficacy and safety

In recent years, experts and international institutes have questioned the safety and health benefits of aspartame. At the same time, researchers and the F&B industry maintain it is one of the most rigorously researched food ingredients. 

In 2023, the WHO and FAO Joint Expert Committee on Food Additives reconfirmed aspartame’s acceptable daily intake level at 40 mg/kg of body weight after the International Agency for Research on Cancer classified it as “possibly carcinogenic to humans.” 

The US FDA recommends limiting intake to 50 mg/kg of body weight. However, the study’s authors claim that aspartame consumption by adults and children “often exceeds those levels,” which Jones calls “extremely unlikely.” 

“I weigh 80 kg, so this means the FDA-based safe dose for me is 4000 mg of aspartame per day, every day, for life,” he details. “Given a diet drink contains about 200 mg of aspartame, I would have to drink the equivalent of 20 cans of diet soda a day to get this dose. A child of 40 kg would have to drink 10 cans daily, every day.”