Low Vitamin D Linked to High IgE, Need for Steroids in Asthma

[補充維他命D可能會減少氣喘嚴重度]

Kate Johnson

March 22, 2012 (Orlando, Florida) — Low serum vitamin D levels in children with asthma are associated with higher immunoglobulin (Ig)E levels and poorer response to inhaled corticosteroids, according to a study reported here at the American Academy of Allergy, Asthma and Immunology (AAAAI) 2012 Annual Meeting.

"Our study suggests that in children there is a window of opportunity to reverse allergic sensitization with vitamin D supplementation,"  said Elena Goleva, PhD, from the Department of Pediatrics at the National Jewish Health in Denver, Colorado.

The study involved 103 people with asthma. Mean serum vitamin D levels were 22 ng/mL for children (n = 53) and 17 ng/mL for adults (n = 50); 47.6% of the cohort was deficient in vitamin D (serum levels below 20 ng/mL).

The researchers found an inverse relation between serum IgE levels and vitamin D in children (P = .006) but not in adults (P = .1693), and an inverse relation between inhaled corticosteroid dose and serum vitamin D levels in children but not adults.

Multivariate regression showed positive correlations between vitamin D levels and the expression of several genes indicative of steroid response — Cyp24a (cytochrome P450, family 24, subfamily a) in children (P = .0084) but not adults, and LL-37 in both children (P = .0006) and adults (P = .0067).

In vitro results also showed that the expression of Cyp24a correlated with the suppression of both interleukin-13 and tumor necrosis factor-alpha by dexamethasone in children (P = .0094 and P = .05, respectively) but not in adults.

Vitamin D Supplementation Debated

"We suggest that supplementation with vitamin D should be done in patients with asthma, both adults and children, to lower steroid requirement and improve steroid response," said Dr. Goleva.

"They jumped to a lot of conclusions. It didn't seem that their data were that strong for making a recommendation as far as supplementation," said a meeting attendee, a researcher with a PhD in nutrition science who asked that her name not be used. "There's still a lot to learn about vitamin D. It is very potent. Modest supplementation might be fine, but some people are giving large doses and we don't know what effect that could have. It could have some negative effects."

Although he did not hear the presentation, Audreesh Banerjee, MD, from the airways biology initiative in the pulmonary, allergy, and critical care medicine division at the University of Pennsylvania in Philadelphia, said that if deficiency in vitamin D increases steroid requirements, there is a possibility that supplementation would decrease steroid needs.

"We've been looking for a long time for steroid-sparing agents. It's not clear that vitamin D would do that, but it could be one strategy, especially if you're really having to go up to high doses of steroids," he told Medscape Medical News.

However, Dr. Banerjee urged caution, because the story of vitamin D and asthma/allergy is still evolving. "Every good scientist and clinician is also a skeptic, so we've got to make sure we see the evidence."

Dr. Goleva and Dr. Banerjee have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma and Immunology (AAAAI) 2012 Annual Meeting: Abstract 483. Presented March 4, 2012.

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