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 administered alongside usual medications. Treatment with vitamin D supplements reduces the risk of asthma attacks requiring hospitalization from 6% to about 3%, and the average annual number of asthma crises per person. However, it does not seem to improve the daily symptoms of the disease.

These data come from a review study recently published in the Cochrane Systematic Reviews and conducted by researchers at Queen Mary University of London (UK).

Does Vitamin D have positive effects on asthma?

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

Asthma manifests with acute episodes and, in some cases, with full asthma attacks involving sudden and intense worsening of respiratory symptoms. Asthma attacks are often triggered by allergens, viruses, physical exertion, and pollution. Treatment consists of anti-inflammatory drugs, corticosteroids, or bronchodilators.

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

A study conducted on 616 asthmatic children in Costa Rica found that 28% of them had vitamin D deficiency (< 30 ng/ml), and this condition was associated with increased blood levels of antibodies and immune cells involved in inflammatory response and bronchial hyperreactivity. A 2015 review study concluded that vitamin D supplementation could reduce the risk of asthma worsening by 74% in children. Additionally, there is evidence for the beneficial role of vitamin D on lung function and steroid response in asthma treatment.

A study on 54 adult asthmatic subjects showed that increased blood vitamin D levels were significantly associated with improved forced expiratory volume in one second (FEV1), a measure of the amount of air exhaled in the first second of a forced maximal expiration.

Drugs and vitamin D supplements reduce risk of severe asthma attacks

The review study examined data from nine studies relating asthma symptoms in adults and children to vitamin D supplementation. The data showed that vitamin D reduced the risk of severe asthma attacks requiring hospitalization from 6% to about 3%.

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

This last data is important since about 50% of asthma sufferers do not experience severe attacks, so vitamin D supplements might have no effect in these individuals. According to Adrian Martineau, professor at Queen Mary College London and author of the study, although many other nutrients have been studied for potential effects in asthma control and prevention, this discovery about vitamin D is the first concrete evidence that a micronutrient can reduce the risk of asthma attacks.

However, the researcher also notes that results should be interpreted cautiously since vitamin D is unlikely to be effective for all asthma patients, not only because of the lack of improvement in daily symptoms, but also because it remains unclear whether vitamin D acts in all patients or only in those deficient at therapy start.

Some details of the study

The review (meta-analysis) study analyzed data from other research on the effect of vitamin D in patients with varying asthma severity.

Nine scientific publications were identified: seven clinical trials involving 435 children and two trials involving 658 adults, conducted up to January 2016. Among these, the study including 22 children and the two adult studies contributed to the analysis of severe asthma attack cases, while most participants had mild to moderate asthma.

The study durations ranged from four to twelve months, and all studies compared vitamin D effects with placebo treatment.

Some questions remain open

This meta-analysis suggests that in people with mild or moderate asthma, vitamin D supplements reduce both disease exacerbation risk and the need for healthcare. However, researchers believe it is premature to recommend vitamin D supplementation without knowing deficiency status, as data do not clarify if there is a vitamin D blood level threshold below which benefits occur.

Further studies are needed focusing on children and those with frequent severe asthma attacks before definitive clinical recommendations can be made. By the end of the year, results of a second meta-analysis will be published to analyze patient subgroups based on their vitamin D blood 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