Table 4.

Summary of major clinical studies evaluating the relationship between vitamin D status and asthma risk

Source	Study design	Condition	Population (cases)	Main outcome(s)
Korn et al91	Prospective study	25(OH)D3 levels <30 ng/mL	280 adult asthma patients	Severe and uncontrolled adult asthma was associated with vitamin D insufficiency and deficiency
Brehm et al169	Cross-sectional study	25(OH)D3 levels <30 ng/mL	616 children (6–14 years)	Vitamin D insufficiency was relatively frequent in an equatorial population of children with asthma; lower vitamin D levels were associated with increased markers of allergy and asthma severity
Bener et al93	Randomized compared trial	25(OH)D3 levels <30 ng/mL	483 children with asthma and 483 healthy controls	The majority of asthmatic children had vitamin D deficiency compared to control children
Freishtat et al89	Cross-sectional case-control study	25(OH)D3 levels <30 ng/mL	92 asthma and 21 controls in African American youths	The prevalence of vitamin D insufficiency and deficiency was significantly greater among asthma cases than control subjects
Brehm et al94	Prospective study	25(OH)D3 levels <30 ng/mL	1,024 children with asthma	Vitamin D insufficiency was associated with higher odds of severe exacerbation over a 4-year period
Morales et al92	Prospective cohort study	Maternal circulating 25(OH)D3 levels	1,724 children	Maternal vitamin D intake resulted in a lower risk of asthma in children at 5 years of age
Gale et al95	Prospective cohort study	25(OH)D3 levels >75 nmol/L	596 pregnant women and 466 children	High vitamin D levels in pregnant women could pose an increased risk of asthma in offspring
Goleva et al90	Prospective cohort study	25(OH)D3 levels <20 ng/mL	205 adults and children	Significant associations between serum vitamin D status and steroid requirement in the pediatric asthma group