Higher levels of circulating vitamin A are linked to better lung function in children and adults with asthma, while vitamin D shows similar benefits in adults, including slower biological ageing, finds the first study of its kind, published online in the respiratory journal Thorax.
Poor lung function is a key predictor of death, irrespective of whether or not a person has lung disease. And making sure that the lungs keep working well is essential for staving off long term respiratory conditions, explain the researchers.
Previously published research suggests that vitamins A and D both protect against and worsen asthma, as well as influencing lung development, depending on the dose and context, they add.
To clarify the role of these vitamins, the researchers drew on two groups of participants with asthma: 1165 children in the GACRS (Genetic Epidemiology of Asthma in Costa Rica Study); and 1041 adults in the ODOLLFA (Omic Determinants of Longitudinal Lung Function in Asthma).
Small molecules that fine-tune the activity of genes (serum microRNAs or miRNAs for short) and those that mark genes as either active or inactive (DNA methylation), plus levels of vitamins A and D, were measured in all the participants.
Lung capacity/health was assessed through measures of forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and the FEV:FVC ratio.
In adults, further analysis assessed whether methylation status and miRNAs influenced the association between the vitamins and lung function or epigenetic ageing—the response of genes to external biological and environmental factors which then promotes cellular ageing.
The findings showed that children and adults with asthma and higher vitamin A levels had better lung function (FEV1 and FVC) than those with lower levels.
And among adults with asthma, those with higher vitamin D levels of at least 30 ng/ml had better lung function than those with lower levels. They also had less evidence of epigenetic ageing, suggesting that vitamin D may help slow biological ageing, particularly in people with asthma, say the researchers.
"These findings emphasise the value of adequate vitamin D, not only for lung health but also in slowing age-related processes," they write.
In people with asthma, vitamin D deficiency is more common and is associated with more severe disease, worse asthma control, higher inhaled steroid need and more frequent sudden worsening of asthma symptoms, they explain.
The researchers identified MiRNAs that regulate 248 genes commonly associated with vitamins A and D in both age groups, which, further analysis suggests, are involved in controlling inflammation and lung function.
This secondary analysis also revealed that changes in the expression of specific miRNAs strongly influence the effects of vitamins A and vitamin D on lung function and epigenetic ageing.
"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," write the researchers.
Lung function was inversely correlated with all age acceleration measures, reinforcing the link between respiratory health and ageing," they add.
They conclude: "Our findings emphasise that epigenetic mechanisms play a key role in mediating the effects of vitamins on lung function in individuals with asthma, pointing to potential targets for personalised nutrition and therapeutic strategies in asthma care."
In a linked editorial, Drs Sze Man Tse and Genevieve Mailhot of the CHU Sainte-Justine Research Center, Montreal, and the University of Montreal, caution: "While these findings open a novel line of investigation linking vitamin D, biological ageing and lung health, there is a need for further studies to clarify causality."
But they add: "By examining the underlying biological mechanisms, [the researchers have] revealed a nuanced interplay between vitamins A and D, lung function, and their epigenetic mediators.
"Their findings highlight age-dependent and age-independent mechanisms, underscoring complex interactions between vitamin levels and lung physiology."
And they conclude: "Overall, advancing our understanding of how nutritional exposures impact gene regulation may open new avenues for managing asthma across the lifespan."
