There was no significant effect for asthma symptom scores and lung function .
Conclusions and Relevance R and omized controlled trials provide some low- quality evidence to support vitamin D supplementation for the reduction of asthma exacerbations .
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 .
GRADE guidelines: 5. Rating the quality of evidence--publication bias.
In the GRADE approach , r and omized trials start as high- quality evidence and observational studies as low- quality evidence , but both can be rated down if a body of evidence is associated with a high risk of publication bias . Even when individual studies included in best- evidence summaries have a low risk of bias , publication bias can result in substantial overestimates of effect . Authors should suspect publication bias when available evidence comes from a number of small studies , most of which have been commercially funded . A number of approaches based on examination of the pattern of data are available to help assess publication bias . The most popular of these is the funnel plot ; all , however , have substantial limitations . Publication bias is likely frequent , and caution in the face of early results , particularly with small sample size and number of events , is warranted
There was no significant effect for asthma symptom scores and lung function .
Conclusions and Relevance R and omized controlled trials provide some low- quality evidence to support vitamin D supplementation for the reduction of asthma exacerbations .
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 .