Vitamin A: Essential Fat-Soluble Nutrient for Vision, Immunity and Lung Health

Vitamin A and Lung Function: New Evidence in Asthma

Higher levels of circulating vitamin A have been found to be significantly associated with better lung function in both children and adults with asthma, according to what researchers describe as the first study of its kind, published online in the respiratory journal Thorax. The study also examined vitamin D, finding that it conferred similar benefits, though these were confined to adults and extended beyond lung function to include slower biological 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."

The researchers drew on two substantial cohorts to test this relationship: 1,115 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, together comprising more than 2,200 participants with asthma. This scale matters, since prior research on the role of vitamins A and D in asthma had produced somewhat inconsistent findings, with both nutrients shown in earlier studies to have protective and, in some cases, adverse effects depending on dosage and context.

What the Researchers Found

The study's senior investigator, Michael McGeachie of Brigham and Women's Hospital, noted that vitamin A's clear positive association with lung health across both age groups was, in fact, an unexpected finding. Beyond the direct effect on lung function, the researchers also detected a meaningful epigenetic signature: adults with sufficient vitamin D levels showed lower biological age acceleration than those with insufficient levels, measured across six distinct epigenetic ageing markers, with differences as large as nearly four years between the two groups on some measures. Lung function itself was found to be inversely correlated with all of these age-acceleration measures, reinforcing a broader link between respiratory health and the pace of biological ageing. The researchers suggested that these effects operate at least partly through gene regulation vitamin exposure appeared to influence methylation patterns and microRNA expression tied to lung development, rather than acting solely through a direct physiological pathway.

An accompanying editorial urged some caution about how far these findings should be extended.

"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."

This caveat is an important one: the study is cross-sectional, meaning it can establish an association between vitamin levels and lung function but cannot on its own confirm that raising vitamin A or D levels through supplementation would actually improve lung function the correlation could partly reflect other healthier behaviours common among people who already have higher vitamin levels.

Understanding Vitamin A

Vitamin A is a fat-soluble vitamin stored primarily in the liver, and although it is often spoken of as a single nutrient, it is really a group of related compounds, including retinol, retinal, and retinyl esters. The diet supplies it in two distinct forms: preformed vitamin A, found in animal products such as meat, fish, poultry, and dairy, and provitamin A, found in plant foods such as fruits and vegetables, of which beta-carotene is the most common example. Whichever form is consumed, the body must convert it into the active compounds retinal and retinoic acid before it can actually be used. Foods particularly rich in vitamin A include beef liver and other organ meats, oily fish such as herring and salmon, eggs, dairy products including cheese and fortified milk, fortified breakfast cereals, and a range of orange, yellow, and dark green vegetables and fruits such as carrots, sweet potatoes, mangoes, cantaloupe, broccoli, and spinach.

Why Vitamin A Matters Beyond Vision

Vitamin A's best-known role lies in vision and eye health it is also known as retinol precisely because it produces the pigments found in the retina, supporting good eyesight, particularly in low light. But its functions extend considerably further: it supports cell growth, immune function, and fetal development, and plays a particularly important role in protecting surface tissues such as the skin, intestines, lungs, bladder, and inner ear a detail that lends biological plausibility to the asthma findings, since maintaining the integrity of lung tissue is directly relevant to respiratory function. Vitamin A also supports immune defence by promoting the growth and distribution of T cells, the white blood cells responsible for protecting the body against infection, and contributes to both male and female reproductive health.

Deficiency in vitamin A carries real risks, ranging from reversible night blindness to xerophthalmia, a form of irreversible corneal damage, and can also produce hyperkeratosis, a condition marked by dry, scaly skin. While deficiency can be corrected with supplementation, excess intake is not without its own dangers — taking too much vitamin A can cause serious side effects and, in extremely high doses, can even prove fatal, underscoring that this is a nutrient where balance matters as much as sufficiency.

Conclusion

This study adds a genuinely novel dimension to the understanding of asthma management by connecting a familiar nutrient to a molecular mechanism epigenetic regulation that had not previously been examined in this context. The finding that vitamin A tracks with better lung function in both children and adults, alongside vitamin D's association with slower biological ageing in adults, opens a promising line of inquiry into nutritional strategies for asthma care. At the same time, the cross-sectional nature of the evidence means any translation into clinical recommendations, such as targeted supplementation, will require further interventional studies to establish whether raising vitamin levels can actually cause improvements in lung function, rather than merely accompanying them.