Vitamins A and D both play roles in immune function, inflammation and development, which has made them a long-running area of interest in asthma research. But their relationship with lung health is not always straightforward.
A new observational study published in Thorax found that higher circulating vitamin A levels were linked with better lung function in children and adults with asthma. In adults, vitamin D levels of at least 30 ng/ml were also linked with better lung function and lower measures of epigenetic aging, a way of estimating biological aging through chemical changes that affect gene activity. The findings point to a possible connection between vitamin status, lung function and gene regulation, but they do not prove that taking vitamin A or D supplements would improve asthma.
The study drew on two groups of people with asthma: 1,165 children from the Genetic Epidemiology of Asthma in Costa Rica Study and 1,041 adults from the Omic Determinants of Longitudinal Lung Function in Asthma study. Researchers measured circulating levels of vitamins A and D, lung function and several markers related to gene regulation, including microRNAs and DNA methylation.
Lung function was assessed with standard breathing measures, including forced expiratory volume in one second, often called FEV1, and forced vital capacity, or FVC. These tests measure how much air a person can forcefully breathe out and are commonly used to evaluate respiratory health.
The main finding was that children and adults with asthma who had higher vitamin A levels also tended to have better FEV1 and FVC scores. Among adults, vitamin D sufficiency, defined in the study as at least 30 ng/ml, was also linked with better lung function. Adults with sufficient vitamin D also showed less evidence of epigenetic age acceleration, suggesting a possible link between vitamin D status, respiratory health and biological aging.
The researchers also looked at molecular clues that might help explain the pattern. They identified microRNAs connected to genes associated with vitamins A and D, many of which are involved in inflammation and lung function. Their analysis suggested that gene-regulation pathways may partly mediate the relationship between vitamin levels and lung function in people with asthma.
“To our knowledge, this is the first study to integrate vitamin A and D levels with lung function and epigenetic markers — miRNA expression and DNA methylation — in both children and adults with asthma,” the researchers wrote.
That makes the study interesting, but not definitive. Because it was observational, it cannot show whether higher vitamin levels caused better lung function or whether vitamin levels are markers of other differences in health, diet, inflammation, sun exposure, medication use or overall disease control.
A linked editorial in Thorax also urged caution, noting that more research is needed to clarify causality. That distinction matters, especially because vitamins can be easy to turn into supplement advice before the evidence supports it.
Vitamin A is a good example. It is essential for immune function, vision and normal growth, but too much vitamin A, particularly from supplements or retinol-containing products, can be harmful. Vitamin D deficiency is also common and has been linked in previous research with worse asthma control, but this study does not show that taking vitamin D improves asthma symptoms, reduces flare-ups or replaces standard asthma care.
The more careful message is that adequate nutrient status may be one piece of asthma and lung-health biology. It may also help researchers understand why some people with asthma have different patterns of inflammation, lung function and aging-related markers.
For people with asthma, the findings should not prompt changes to medication or supplement routines without medical guidance. Asthma treatment still depends on established care plans, including prescribed inhalers and trigger management. Anyone concerned about vitamin levels can ask a clinician whether testing or supplementation is appropriate.
The study’s value is less about offering a new at-home fix and more about pointing researchers toward a more nuanced question: how nutrition-related biomarkers may interact with the immune system, gene regulation and lung function across the lifespan.
The study used data and biological samples from the GACRS and ODOLLFA cohorts. Molecular data for the Trans-Omics in Precision Medicine, or TOPMed, program were supported by the National Heart, Lung, and Blood Institute. Additional support included TOPMed metabolomics, data coordinating, DNA methylation and related infrastructure funding. One author reported being a scientific adviser to Antipode and TruDiagnostic and receiving funding from TruDiagnostic. Another reported being a board member of Histolix and receiving royalties from UpToDate.