May 18, 2026, 3:12 pm | Read time: 6 minutes
Soft drinks, chips, sweets, or frozen pizza are a regular part of many children’s daily lives. However, these highly processed foods are now the focus of a new study from Spain. Researchers followed hundreds of children over several years and discovered a noticeable link between diet and respiratory health. FITBOOK explains what the results mean and what parents can learn from them.
What’s Behind the Asthma Suspicion?
Asthma and allergies are among the most common chronic diseases in childhood. While genetic predisposition is considered a significant risk factor, experts have suspected for years that diet might also influence their development.
The current study focused on so-called ultra-processed foods. These include heavily processed industrial products like soft drinks, chips, sweets, fast food, frozen pizza, packaged snacks, sweetened milk drinks, and many breakfast cereals from the supermarket. They often contain a lot of sugar, salt, saturated fats, and additives, but little fiber.1
Previous Studies Already Provided Initial Clues
Previous studies had already provided clues about a link between these products and respiratory problems.2,3,4 However, many of these studies were only snapshots, making it difficult to assess whether dietary habits existed before the disease.
The researchers of the Spanish SENDO project wanted to examine this more closely. They investigated whether children with high consumption of ultra-processed foods were more likely to develop asthma or other allergic diseases later.
How Researchers Observed the Children Over Years
For the study, researchers followed 691 children aged four to five years over several years. On average, the children were observed for about three and a half years.5
Parents Documented the Diet
It wasn’t the children themselves but their parents who provided the information. They answered detailed questionnaires about what their children regularly eat and drink. Based on this information, the researchers calculated the proportion of ultra-processed foods in the overall diet. Children with particularly high consumption derived more than 30 percent of their daily energy intake from such products.
Annual Check for Asthma and Allergies
Each year, it was recorded whether the children had been newly diagnosed with asthma or other allergic diseases. Additionally, the scientists considered other factors that could influence the risk, such as body weight, screen time, breastfeeding, parental smoking, and the family’s nutritional knowledge.
Noticeable Differences in the Children’s Daily Lives
Notably, children with high consumption of ultra-processed foods tended to spend more time in front of screens, were slightly less active, and were less often exclusively breastfed. According to the study, their parents also had less knowledge about dietary recommendations for children.
Children who already had asthma or the respective disease at the start were excluded from the analyses to ensure only newly occurring cases were considered.
Striking Result: More Processed Foods, More Asthma
During the observation period, 34 children were newly diagnosed with asthma. The difference between children with low and high consumption of ultra-processed foods was particularly pronounced.
According to the study, children with a particularly high proportion of such products in their diet had an almost fourfold increased risk of developing asthma later.
A clear trend showed: Children with higher consumption had a significantly higher risk of asthma than those who ate little processed food. The researchers, therefore, speak of a possible “dose-response relationship.” Simply put, it wasn’t a single burger or bag of chips that was decisive, but the long-term dietary pattern over the years.
For other conditions like eczema, food allergies, or allergic asthma, the scientists found no comparable link.
Why Experts Are Taking a Closer Look Now
The study suggests that diet may play a larger role in asthma than previously thought. Particularly relevant is that the children were followed over several years, allowing researchers to better understand that dietary habits existed before the diagnoses.
The authors suspect that ultra-processed foods could promote inflammatory processes in the body. Possible causes include saturated fats and so-called AGEs, substances that can form during heavy industrial processing or heating.
Researchers Suspect “Silent Inflammation” as a Trigger
These substances could activate certain inflammatory pathways in the body. Researchers suspect this could lead to a persistent mild inflammatory reaction—often called “silent inflammation.” It could make the airways more sensitive and promote long-term changes in the bronchi.
It is also notable that asthma occurred more frequently, while classic allergies did not. This could indicate that the foods promote general inflammatory reactions rather than typical allergic processes.
For families, this doesn’t mean that individual snacks or processed products directly cause asthma. The study emphasized the long-term dietary pattern and the overall high proportion of heavily processed products.
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What to Consider About the Results
Despite the striking results, the study does not prove that ultra-processed foods actually cause asthma. It is an observational study, and other factors could also have played a role.
Another limitation is that the diet was not directly measured but recorded through parental reports. While such questionnaires are standard in nutritional studies, they are not perfect. People don’t always accurately remember what or how often they ate.
An Important Point Limits the Significance
Additionally, the number of new asthma cases was relatively small (34 new asthma cases), making the results less clear-cut than they might initially appear. Further studies are needed to confirm the connection.
One point to keep in mind: The study primarily involved families with a high level of education. Whether the results apply to all families must be shown by further investigations.
The researchers themselves emphasize that more studies are needed to confirm the results and examine possible biological causes in more detail.
The SENDO project, a Spanish long-term study on the healthy development of children, was funded by the MAPFRE Foundation. According to the study, the authors did not report any conflicts of interest.
Conclusion: Diet May Be More Important Than Thought
The Spanish SENDO study suggests that high consumption of ultra-processed foods may be linked to an increased risk of asthma in children. Children whose diets largely consisted of heavily processed products were particularly affected.
For other allergic diseases, the researchers found no comparable link. The results mainly provide clues about possible inflammatory processes in the body.
Even though the study does not prove causation, it supports the recommendation to feed children as varied a diet as possible and with few heavily processed products.