Meta- analysis of a modest number of trials in people with predominantly mild to moderate asthma suggests that vitamin D is likely to reduce both the risk of severe asthma exacerbation and healthcare use .
Children and people with frequent severe asthma exacerbations were under-represented ; additional primary trials are needed to establish whether vitamin D can reduce the risk of severe asthma exacerbation in these groups
BACKGROUND Several clinical trials of vitamin D to prevent  asthma exacerbation  and improve  asthma control  have been conducted in children and adults , but a meta- analysis restricted to double-blind , r and omised , placebo-controlled trials of this intervention is lacking .
OBJECTIVES To evaluate the efficacy of administration of vitamin D and its hydroxylated metabolites in reducing the risk of severe asthma exacerbations ( defined as those requiring treatment with systemic corticosteroids ) and improving asthma symptom control .
Distinct endotypes of steroid-resistant asthma characterized by IL-17Ahigh and IFN-γhigh immunophenotypes: Potential benefits of calcitriol
Background A small population of patients with severe asthma does not respond to glucocorticoids ( steroid resistant [ SR ] ) . They have high morbidity , highlighting an urgent need for strategies to enhance glucocorticoid responsiveness . Objective We investigated the immunologic differences between steroid-sensitive ( SS ) and SR asthmatic patients and the effect on immunophenotype of oral calcitriol treatment because it has been previously shown to beneficially modulate the clinical response to glucocorticoids in patients with SR asthma . Methods CD8-depleted P BMC s were isolated from 12 patients with SS and 23 patients with SR asthma and cultured for 7 days with anti-CD3 and IL-2 with or without dexamethasone . Cytokine production was assessed in supernatants by using the Cytometric Bead Array . Patients with SR asthma were subsequently r and omized to oral calcitriol or placebo therapy , and identical studies were repeated . Results Patients with SR asthma produced significantly increased IL-17A and IFN-γ levels compared with those in patients with SS asthma , although it was evident that cells from individual patients might overproduce one or the other of these cytokines . Production of IL-17A was inversely and production of IL-13 was positively associated with the clinical response to prednisolone . Oral calcitriol , compared with placebo , therapy of the patients with SR asthma significantly improved dexamethasone-induced IL-10 production in vitro while suppressing dexamethasone-induced IL-17A production . This effect mirrored the previously demonstrated improvement in clinical response to  oral glucocorticoids  in calcitriol-treated patients with SR asthma . Conclusions IL-17Ahigh and IFN-γhigh immunophenotypes exist in patients with SR asthma . These data identify immunologic pathways that likely underpin the beneficial clinical effects of calcitriol in patients with SR asthma by directing the SR cytokine profile toward a more SS immune phenotype , suggesting strategies for identifying vitamin D responder immunophenotypes
Meta- analysis of a modest number of trials in people with predominantly mild to moderate asthma suggests that vitamin D is likely to reduce both the risk of severe asthma exacerbation and healthcare use .
Children and people with frequent severe asthma exacerbations were under-represented ; additional primary trials are needed to establish whether vitamin D can reduce the risk of severe asthma exacerbation in these groups
BACKGROUND Several clinical trials of vitamin D to prevent  asthma exacerbation  and improve  asthma control  have been conducted in children and adults , but a meta- analysis restricted to double-blind , r and omised , placebo-controlled trials of this intervention is lacking .
OBJECTIVES To evaluate the efficacy of administration of vitamin D and its hydroxylated metabolites in reducing the risk of severe asthma exacerbations ( defined as those requiring treatment with systemic corticosteroids ) and improving asthma symptom control .