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Document Type

Open Access

Degree Program

Nutrition

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2011

Month Degree Awarded

February

Keywords

Serum 25(OH)D, Dietary Vitamin D, Asthma

Abstract

Although maternal vitamin D status has been linked to asthma in offspring, the relationship between vitamin D status and asthma in adults still remains unclear. The current study assessed the relationship between measures of vitamin D status and self-reported asthma/wheeze in 186 healthy women aged 18-30 years. Although the risk of asthma/wheeze symptoms was three-times higher among women with low dietary vitamin D intake (<200 IU>/day) than in those with higher vitamin D intake, suboptimal serum levels of 25(OH)D ( <70 nmol>/L) were associated with a 48% lower risk of asthma/wheeze than “optimal” serum levels. These contradictory effects underscore the poor correlation between dietary vitamin D intake and serum vitamin levels and suggest that other components in vitamin D-rich foods may be protective. Alternatively, women with higher serum vitamin D levels may have spent more time outdoors, increasing their exposure to asthma triggers. This study also identified predictors of serum 25 (OH) D in this sample. In addition to total dietary vitamin D (r= 0.2; p=0.03), intake of cold cereal (p=0.02) also significantly predicted serum 25(OH)D levels. Among non-dietary factors, month of blood draw (p=0.05) and oral contraceptive use (p<0.0001) were positive predictors of serum 25(OH) D; sunscreen use (p=0.04) was a negative predictor. After adjusting for covariates, oral contraceptive use was associated with 25(OH)D levels that were on average 24 nmol/L greater than those observed in women who did not use oral contraceptives. Additional prospective studies are needed to further evaluate the relationship between vitamin D status and asthma.

First Advisor

Alayne G Ronnenberg

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