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 .
Prevention of corticosteroid-induced osteoporosis by alfacalcidol
Summary We studied the effect of alphacalcidol ( 1-α-hydroxycholecalciferol ) on bone metabolism in patients who were placed on glucocorticoid therapy .  We selected 41 women ( age : 32–52 yrs ) who were recently diagnosed with systemic lupus erythematodes , multiple sclerosis , rheumatoid arthritis or asthma bronchiale . Patients did not have other disease or take drugs known to influence bone metabolism . Patients were r and omly enrolled into two groups and were given 5–25 mg prednisone daily . After 4 weeks , group A ( n=21 ) received 0.5–1.0μg ( mean=0.54±0.03μg ) alphacalcidol and group B ( control ; n=20 ) was given 500 mg calcium daily for three years . There were no significant differences in age and steroid doses between groups . Serum calcium ( Ca ) , osteocalcin ( OC ) , collagen I C-terminal propeptide ( PICP ) , parathyroid hormone ( PTH ) , and urinary calcium and deoxypyridinoline crosslink excretion ( DPD ) were measured before corticosteroid administration , and before alphacalcidol or calcium treatment as well as 6 weeks , 6 months , and 1 , 2 , and 3 years later . Bone mineral density ( BMD ) was examined before treatment and 6 months , 1 , 2 , and 3 years later by DEXA and SPA . OC and PICP decreased significantly after 4 weeks on steroid in both groups and increased in group A but not in group B after 6 weeks of treatment with alphacalcidol and remained unchanged for 3 years . Serum PTH increased in both groups after 4 weeks of glucocorticoid treatment and was reduced in group A , but not in group B , after 6 weeks on alphacalcidol . Serum Ca , urinary Ca , and DPD did not change significantly in either group during the study period . Lumbar spine and femoral neck BMD were significantly reduced in group B after 6 months and 1 year , respectively , and continued to decrease during the study , while no significant change in group A was observed . BMD of the radius did not change in either group for 2 years but there was a significant reduction by the third year in group B. Based on these results , alphacalcidol treatment appears to be effective in preventing glucocorticoid-induced bone loss in these patients by reducing secondary hyperparathyroidism and stimulating bone formation
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 .