“Sugar isn’t just an empty calorie; it’s an active inflammatory agent,” said researcher Mateus Casaro (image by fabrikasimf/Magnific)

Published on 08/03/2026

By Maria Fernanda Ziegler  |  Agência FAPESP – Sugar consumption has been linked to an increased risk of cavities and weight gain. In the long term, it may also contribute to insulin resistance and diabetes. For people living with asthma, however, the impact can be even greater. A study with mice published in the journal Nutrients showed that the intake of high doses of sugar severely worsens lung inflammation in the short term, aggravating the risk of allergic attacks.

In the study, which was conducted in Brazil with support from FAPESP, mice received their regular diet and were given free access to condensed milk. In just two weeks – the equivalent in mice to approximately two years in a human’s life – the animals experienced negative effects. 

According to the researchers, this is the first study to demonstrate how quickly sugar can worsen inflammatory conditions in an experimental asthma model.

“When a child consumes a lot of sugar, we think of consequences such as tooth decay or obesity. But we rarely consider that, in such a short period, a pre-existing allergy could be aggravated,” comments Caroline Marcantonio Ferreira, a professor at the Federal University of ABC (UFABC) who coordinated the study while working at the Federal University of São Paulo (UNIFESP).

The researcher assesses that this finding reinforces the need for initiatives aimed at reducing sugar intake, especially among vulnerable populations, such as children and people with chronic respiratory diseases.

Risk factor

Asthma, a chronic inflammatory disease of the airways, affects approximately 300 million people worldwide. Its prevalence has increased in recent decades. The disease is characterized by changes to the respiratory system due to the inflammatory response.

The bronchioles, tubes that conduct air to the lungs, grow thicker. Besides the narrowing of the airways, there is an increase in mucus production in the bronchi, which accumulates and further impedes airflow. 

The body activates a systemic immune response similar to an allergic reaction, which involves the release of pro-inflammatory molecules (cytokines IL-4, IL-33, and TNF-α, for example) and the production of specific antibodies (immunoglobulin E). All of this process causes symptoms such as difficulty breathing, wheezing, and a persistent cough.  
 
Based on their findings, the researchers warn that people with asthma should monitor their sugar intake as closely as they monitor mold, dust, and pollution in their environment, as these are all potential asthma attack triggers. 

“Sugar isn’t just an empty calorie; it’s an active inflammatory agent capable of altering the immune balance long before any visible weight gain occurs. And it’s important to remember that dietary adjustments are a low-cost, accessible, and extremely effective strategy that should be implemented alongside medication for patients with asthma,” says Mateus Casaro, a FAPESP PhD scholarship holder and co-author of the study. 

The origin of the inflammation

Through experiments conducted with mice, the researchers demonstrated that sugar causes systemic inflammation that begins in abdominal fat, affecting vital organs such as the liver, pancreas, and intestines. This fat, known as visceral adipose tissue, begins to produce inflammatory substances, such as leptin and cytokines, that travel throughout the body and intensify the allergic response in the lungs. Analyses also indicate that inflammatory defense cells (M1-type macrophages) can migrate from abdominal fat to the lungs.

“This is the leading hypothesis to explain why sugar worsens asthma-related inflammation. We observed that sugar causes inflammation in adipose tissue, even in animals that don’t have asthma. In those that consume sugar but aren’t allergic, the lungs remain normal, but the fat becomes inflamed. This suggests that the process begins in the fat and that substances released there eventually migrate to the lungs, where they intensify an existing allergic response,” Ferreira explains.

Although the study was conducted specifically for asthma, Ferreira states that it is possible sugar exacerbates inflammation in other organs as well, even in the short term. “We conducted a similar study on dermatitis. The results showed an exacerbation of skin inflammation over a short period,” she says.

The researchers emphasize that a high-sugar diet cannot cause asthma on its own but can amplify existing inflammation. “No animal without induced asthma developed the disease after consuming large amounts of condensed milk. However, in animals that already had allergic sensitivity, sugar drastically increased mucus in the airways and the recruitment of inflammatory cells,” Ferreira explains. 

The article “A short-term high-sugar diet induces glucose intolerance, visceral adipose tissue inflammation, and exacerbates experimental allergic asthma” can be read at www.mdpi.com/2072-6643/18/9/1475. 

 

Source: https://agencia.fapesp.br/58859