Overview
Diet is increasingly recognized as a potential factor in asthma, but asthma is not a single disease. It is a heterogeneous condition made up of different endotypes, meaning biologically distinct subtypes driven by different immune pathways. This study examined whether dietary patterns were linked to a specific asthma endotype, especially T helper 17 high asthma, in Puerto Rican children and adolescents.
Puerto Rican youth are an important population to study because asthma is common and often severe in this group. Understanding how diet may influence asthma biology could help identify modifiable risk factors and support more personalized prevention strategies.
Why this study matters
Asthma can arise through different inflammatory pathways. Two of the best studied are T helper 2, or T2, and T helper 17, or T17, immune responses. T2-high asthma is often associated with allergic inflammation, while T17-high asthma may involve neutrophilic inflammation and can be harder to treat with standard allergy-focused therapies.
Researchers wanted to know whether an unhealthy diet was associated with T17-high asthma, both at one point in time and over several years. If a relationship exists, it could suggest that diet influences asthma through immune mechanisms beyond classic allergy pathways.
Study design
This was a cross-sectional and longitudinal study of Puerto Rican children and adolescents with asthma and without asthma.
The investigators analyzed:
– Cross-sectional data from 465 participants at a second study visit
– Longitudinal data from 358 participants who completed both a baseline visit and a follow-up visit
Participants were between 6 and 14 years old at the first visit and 9 to 20 years old at the second visit. The average time between visits was 5.3 years.
Diet was assessed using a food frequency questionnaire. Based on those responses, researchers created a dietary score ranging from -2, representing the least healthy pattern, to +2, representing the healthiest pattern. For analysis, an unhealthy diet was defined as a nonpositive score, meaning -2 to 0.
To classify asthma endotypes, the team measured expression of eight signature genes in nasal epithelial cells related to T2 and T17 immunity. At the second visit, three asthma endotypes were identified:
– T2-high
– T17-high
– T2-low/T17-low
The main statistical method was multinomial regression, which is useful when comparing several outcome groups at once.
Main findings
In the cross-sectional analysis, among 465 participants at the second visit, the healthiest diets were linked to lower odds of T17-high asthma. Specifically, each one-point increase in dietary score was associated with a 28% lower odds of T17-high asthma compared with the control group, with an odds ratio of 0.72.
In contrast, having an unhealthy diet was associated with more than twice the odds of T17-high asthma. The odds ratio was 2.31, meaning the association was statistically significant and unlikely to be due to chance.
In the prospective analysis, which included 356 youths who completed both visits, the signal was even stronger. Participants who had an unhealthy diet at both visits had increased odds of:
– T17-high asthma, with an odds ratio of 4.30
– T2-low/T17-low asthma, with an odds ratio of 2.48
These findings suggest that long-term exposure to an unhealthy dietary pattern may be more strongly associated with certain asthma endotypes than diet measured at just one time point.
What the results may mean
The findings support the idea that diet may influence asthma through immune pathways, particularly the T17 pathway. T17-associated inflammation has been linked to more persistent or treatment-resistant forms of asthma in some patients. If diet contributes to this pathway, it could partly explain why some children and adolescents experience more severe or less typical asthma patterns.
The study does not prove that diet causes T17-high asthma. Because the analysis was observational, other factors may also play a role, such as body weight, socioeconomic status, environmental exposures, physical activity, or overall health behaviors. Still, the association remained notable after multivariable analysis, which strengthens the argument that diet could be an important contributor.
Clinical and public health implications
This study adds to growing evidence that asthma prevention and management should look beyond inhalers alone. For children and adolescents, especially those in high-risk populations, diet may be one potentially modifiable factor worth addressing.
A healthier dietary pattern generally means more fruits, vegetables, whole grains, legumes, and less highly processed food, sugar-sweetened beverages, and excess saturated fat. While the study did not test a specific diet prescription, its findings are consistent with broader nutrition research showing that overall diet quality can influence inflammation and immune function.
For clinicians, the message is not that diet replaces standard asthma care, but that nutrition counseling may be a useful part of comprehensive asthma management. For families, improving diet quality may offer benefits beyond asthma, including better cardiovascular, metabolic, and general health.
Study strengths and limitations
One strength of this study is that it included both cross-sectional and longitudinal analyses, allowing researchers to examine both current associations and longer-term patterns. Another strength is the use of molecular markers from nasal epithelial cells to define asthma endotypes, which provides a more biologically precise picture than symptoms alone.
However, there are limitations. The study was observational, so causality cannot be established. Diet was based on questionnaire data, which can be affected by recall bias. The sample was limited to Puerto Rican youth, which is important scientifically but may affect how broadly the results apply to other populations. In addition, asthma endotypes can change over time, and nasal gene expression is only one window into airway biology.
Bottom line
In Puerto Rican children and adolescents, an unhealthy diet was associated with higher odds of T17-high asthma in both cross-sectional and prospective analyses. These findings suggest that dietary patterns may influence asthma through T17 immune pathways and highlight diet as a potentially modifiable factor in asthma prevention and care.
More research is needed to determine whether improving diet quality can actually reduce the risk or severity of T17-high asthma and whether similar findings occur in other populations.
