Asthma: vitamin D supplements protect against acute attacks and reduce the risk of hospitalization

Asthma: vitamin D protects against acute attacks

Vitamin D supplements can moderate the symptoms and severity of asthma when given along with the usual medications. In fact, treatment with vitamin D supplements reduces the risk of asthma attacks requiring hospitalization, and the average annual number of asthma attacks, per person from 6 percent to about 3 percent. It does not, however, appear to improve daily symptoms of the disease.

These are the data reported by a review study published just in the past few days, in the Cochrane Systematic Rewievs and carried out by researchers at Queen Mary University of London, UK.

Does vitamin D have positive effects on asthma?

Asthma is a chronic respiratory disease that affects about 300 million people worldwide. The condition is characterized by recurrent episodes of dyspnea (shortness of breath), wheezing, chest constriction and coughing, particularly early in the morning and during the night often causing disturbed sleep.

Asthma manifests as acute episodes and, in some cases, true asthma crises that see a sudden and intense worsening of respiratory symptoms. Asthma crises are often caused by allergens, viruses, physical exertion, and pollution. Treatment of asthma is anti-inflammatory drugs, corticosteroids, or bronchodilators. 

Recently, a role of vitamin D, long studied for its importance in growth and maintenance of bone health, has also been hypothesized in allergic diseases and asthma, and a potential role of vitamin deficiency in the onset of asthmatic disease. It has recently been shown that low vitamin D levels are associated with an increased risk of developing allergic disease, bronchial hyperactivity, and asthma. 

Una ricerca condotta su 616 bambini asmatici del Costa Rica ha evidenziato come ben il 28% di essi presentava una carenza di vit.D (< 30ng per ml), e che questa condizione si associava ad aumento del livello nel sangue di anticorpi e cellule del sistema immunitario coinvolte nella risposta infiammatoria e nella iperattività bronchiale. Uno studio di revisione, nel 2015, ha concluso che l’integrazione con la vitamina D potrebbe ridurre il rischio di peggioramento dell’asma nel 74% nei bambini. Inoltre, esistono evidenze circa il ruolo benefico della vitamina D sulla funzione polmonare e sulla risposta agli steroidi nel trattamento dell’asma. 

A study of 54 adult asthmatic subjects showed that increased blood levels of the vitamin were significantly associated with improved maximum expiratory volume (a measure that indicates the amount of air exhaled in the first second of a forced maximum exhalation).

Drugs and vitamin D supplements reduce the risk of severe asthma attacks 

The review study examined data from nine research studies that related asthma symptoms in adults and children and dietary supplementation with vitamin D. The data proved that the latter was able to reduce the risk of severe asthma attacks, and requiring hospitalization, from 6 percent to about 3 percent. 

Following supplementation, then, the rate of asthma attacks requiring steroid treatment had dropped from 0.44 to 0.28 per person, per year, but the vitamin D supplements had not improved lung function or common daily symptoms. 

This last finding is very important because about 50 percent of asthma sufferers do not experience severe attacks, so in these individuals vitamin D supplements may have no effect. According to Adrian Martineau, professor at Queen Mary College London and author of the study, although many other nutrients have been studied to discover a potential effect in asthma control and prevention, this finding on vitamin D is the first concrete evidence of how a micronutrient can reduce the risk of asthma attacks. 

In any case, again according to the researcher, the results should be interpreted with caution as it appears rather unlikely that vitamin D will be effective for all asthma patients, not only because of the failure to improve daily symptoms of the disease, but also because it is not yet clear whether vitamin D can act in all patients or simply in those who are deficient in it at the beginning of therapy.

Some details of the work

In the review study, or meta-analysis, which analyzes the set of data obtained from other research on a given topic, the action of vitamin D in asthma patients of different severities was examined. 

Nine scientific publications were identified: seven clinical trials involving 435 children and two trials conducted on 658 adults, performed through January 2016. Of these, the study involving 22 children and the two on adults contributed to the analysis of cases of severe asthma attacks, while most of the participants involved suffered from a mild or moderate form. 

The duration of the various researches ranged from four to 12 months, and all studies had compared the effects of vitamin D with a placebo treatment.

Some questions remain unanswered

This meta-analysis, according to the researchers who conducted it, suggests that in people with mild to moderate asthma, vitamin D supplements are able to reduce both the risk of disease exacerbation and the need for health care. In any case, the researchers themselves, still do not believe it is appropriate to suggest vitamin D supplementation without knowing whether one is deficient or not, as it is not clear from the data obtained that there is a threshold of vitamin D in the blood below which one can have benèfits. 

Further studies focusing on children and people who suffer frequent severe asthma attacks are also needed before final clinical recommendations can be issued. Results of a second meta-analysis are expected to be published by the end of the year to analyze subgroups of patients and classify them according to their blood vitamin D levels.   

Source: A. R. Martineau, C. J. Cates, M. Urashima, M. Jensen, A. P. Griffiths, U. Nurmatov, A. Sheikh, C. J. Griffiths "Vitamin D for the management of asthma. Cochrane Database of Systematic Reviews.