Vitamin D and asthma: another dimension

Vitamin D Supplementation for Childhood Asthma: A Systematic Review and Meta-Analysis

Importance

There is growing evidence that vitamin D plays a role in the pathogenesis of asthma but it is unclear whether supplementation during childhood may improve asthma outcomes.

Objectives

The objective of this systematic review and meta-analysis was to evaluate the efficacy and safety of vitamin D supplementation as a treatment or adjunct treatment for asthma.

Data Sources

We searched MEDLINE, Embase, CENTRAL, and CINAHL through July 2014.

Study Selection

We included RCTs that evaluated vitamin D supplementation in children versus active control or placebo for asthma.

Data Extraction and Synthesis

One reviewer extracted data and one reviewer verified data accuracy. We qualitatively summarized the main results of efficacy and safety and meta-analyzed data on comparable outcomes across studies. We used GRADE for strength of evidence.

Main Outcome Measures

Main planned outcomes measures were ED visits and hospitalizations. As secondary outcomes, we examined measures of asthma control, including frequency of asthma exacerbations, asthma symptom scores, measures of lung function, β₂-agonist use and daily steroid use, adverse events and 25-hydroxyvitamin D levels.

Results

Eight RCTs (one parallel, one crossover design) comprising 573 children aged 3 to 18 years were included. One study (moderate-quality, n = 100) reported significantly less ED visits for children treated with vitamin D. No other studies examined the primary outcome (ED visits and hospitalizations). There was a reduced risk of asthma exacerbations in children receiving vitamin D (low-quality; RR 0.41, 95% CI 0.27 to 0.63, 3 studies, n = 378). There was no significant effect for asthma symptom scores and lung function. The serum 25(OH)D level was higher in the vitamin D group at the end of the intervention (low-quality; MD 19.66 nmol/L, 95% CI 5.96 nmol/L to 33.37 nmol/L, 5 studies, n = 167).

Limitations

We identified a high degree of clinical diversity (interventions and outcomes) and methodological heterogeneity (sample size and risk of bias) in included trials.

Conclusions and Relevance

Randomized controlled trials provide some low-quality evidence to support vitamin D supplementation for the reduction of asthma exacerbations. Evidence on the benefits of vitamin D supplementation for other asthma-related outcomes in children is either limited or inconclusive. We recommend that future trials focus on patient-relevant outcomes that are comparable across studies, including standardized definitions of asthma exacerbations.

Vitamin D deficiency and level of asthma control in women from North of Jordan: a case-control study

INTRODUCTION

Reduced vitamin-D levels in patients with asthma have been associated with impaired lung function, increased airway hyper-responsiveness, and reduced glucocorticoid responsiveness. Nationwide studies revealed a considerable prevalence of vitamin-D deficiency (VDD) in Jordanian women.

OBJECTIVE

A case-control study was conducted to determine the relationship between serum vitamin A and D levels and asthma among women in North of Jordan.

METHODS

Sixty-eight asthmatics, age range between 14 and 65 years and 77 healthy women, age range between 19 and 51 years, were enrolled. Asthma severity was classified using Global Initiative for Asthma (GINA) guidelines and Asthma Control Test (ACT) questionnaire. Serum vitamin-A and 25-hydroxyvitamin-D (25(OH)D3) levels were measured using high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods, respectively.

RESULTS

The prevalence of VDD (<15 ng/ml) was higher but not statistically significant for women with asthma compared with controls (95.6% vs. 87.0%; p = 0.070). The severity of VDD correlated with the number of asthma medications (p = 0.020). 25(OH)-D3 serum levels directly correlated with asthma control level using ACT score (p = 0.012) and GINA classification (p = 0.046). After adjusting for age, the odds of having VDD for asthmatic women were 35.9 times higher than that for women with no asthma. There was no difference in serum vitamin-A level between healthy and asthmatic women (p = 0.214) and none had vitamin-A deficiency (<200 µg/dl).

CONCLUSIONS

VDD is prevalent in women with asthma in northern Jordan. The severity of VDD correlated with poor asthma control and a need for more medications to control asthma. There was no association between vitamin-A and asthma.

Effects of vitamin D on immune disorders with special regard to asthma, COPD and autoimmune diseases: a short review

This paper reviews the recent data on the role of vitamin D (VD) in the genesis of various immunological disorders. It inhibits immune reactions in general, but it enhances the transcription of 'endogenous antibiotics' such as cathelicidin and defensins. VD inhibits the genesis of both Th1- and Th2-cell mediated diseases. The pleiotropic character VD-induced effects are due to the altered transcription of hundreds of genes. VD supplementation in most related studies reduced the prevalence of asthma. Th1-dependent autoimmune diseases (e.g., multiple sclerosis, Type 1 diabetes, Crohn's disease, rheumatoid arthritis and so on) are also inhibited by VD due to inhibition of antigen presentation, reduced polarization of Th0 cells to Th1 cells and reduced production of cytokines from the latter cells. VD seems to also be a useful adjunct in the prevention of allograft rejection. Last but not least, VD supplementation may be useful in the prevention or adjunct treatment of chronic obstructive pulmonary disease.