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 .
Vitamin D Supplementation and the Risk of Colds in Patients with Asthma.
RATIONALE Restoration of vitamin D sufficiency may reduce asthma exacerbations , events that are often associated with respiratory tract infections and cold symptoms . OBJECTIVES To determine whether vitamin D supplementation reduces cold symptom occurrence and severity in adults with mild to moderate asthma and vitamin D insufficiency . METHODS Colds were assessed in the AsthmaNet VIDA ( Vitamin D Add-on Therapy Enhances Corticosteroid Responsiveness ) trial , in which 408 adult patients were r and omized to receive placebo or cholecalciferol ( 100,000 IU load plus 4,000 IU/d ) for 28 weeks as add-on therapy . The primary outcome was cold symptom severity , which was assessed using daily scores on the 21-item Wisconsin Upper Respiratory Symptom Survey . MEASUREMENTS AND MAIN RESULTS A total of 203 participants experienced at least one cold .  Despite achieving 25-hydroxyvitamin D levels of 41.9 ng/ml ( 95 % confidence interval [ CI ] , 40.1 - 43.7 ng/ml ) by 12 weeks , vitamin D supplementation had no effect on the primary outcome : the average peak WURSS-21 scores ( 62.0 [ 95 % CI , 55.1 - 68.9 ; placebo ] and 58.7 [ 95 % CI , 52.4 - 65.0 ; vitamin D ] ; P = 0.39 ) . The rate of colds did not differ between groups ( rate ratio [ RR ] , 1.2 ; 95 % CI , 0.9 - 1.5 ) ; however , among African Americans , those receiving vitamin D versus placebo had an increased rate of colds ( RR , 1.7 ; 95 % CI , 1.1 - 2.7 ; P = 0.02 ) . This was also observed in a responder analysis of all subjects achieving vitamin D sufficiency , regardless of treatment assignment ( RR , 1.4 ; 95 % CI , 1.1 - 1.7 ; P = 0.009 ) . CONCLUSIONS Our findings in patients with mild to moderate asthma undergoing an inhaled corticosteroid dose reduction do not support the use of vitamin D supplementation for the purpose of reducing cold severity or frequency
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 .