Vitamin D Deficiency as a Risk Factor for Childhood Allergic Disease and Asthma

Augusto A. Litonjua

Disclosures

Curr Opin Allergy Clin Immunol. 2012;12(2):179-185. 

In This Article

Abstract and Introduction

Abstract

Purpose of review Over the past 2 years, the number of studies relating vitamin D deficiency and asthma and allergies has increased significantly. The purpose of this review is to update the last review in this journal and examine the evidence of the relationship between vitamin D deficiency and childhood asthma and allergies.
Recent findings In the past 2 years since the last review, there have been many studies, both cross-sectional and prospective, that have investigated the effects of vitamin D on the inception and severity of asthma and allergies. Most, but not all, studies have shown that low vitamin D levels increase the risk for asthma and allergies, but a few suggest an increased risk with high levels. Results from small trials of short duration suggest that vitamin D supplementation decreases severity of eczema and decreases the risk for asthma exacerbations.
Summary Data that vitamin D deficiency results in increased risks for asthma and allergies continues to accumulate. However, the optimal level of vitamin D that decreases both the risk for development and severity of these disorders remains elusive. Results of ongoing clinical trials of vitamin D supplementation will be needed before recommendations can be firmly established.

Introduction

Asthma and allergies are common chronic diseases in industrialized countries.[1–3] By the year 2025, as more communities adopt a westernized lifestyle and become urbanized, it is expected that there will be 400 million people worldwide with asthma. In the US, recent reports from national surveys show that the prevalence of asthma continues to rise in both children and adults, and in all racial and ethnic groups.[4,5] Among children (<18 years old), the prevalence of asthma increased from 8.7% in 2001 to 9.6% in 2009.[4] The highest rates were observed among poor children, non-Hispanic Black children, and the northeast.

Whereas data are not as detailed as those for asthma, other allergic disorders have also shown increases. For eczema, wide variations in prevalence have been documented in different parts of the world, with the largest rates in developed countries.[6] In the International Study of Asthma and Allergies in Childhood (ISAAC), eczema prevalence was seen to increase in developing countries over a 5–10-year period between surveys.[7] Similar patterns have been seen for allergic rhinitis.[8]

Whereas many potential reasons could account for the pattern of increased allergic disease in developed countries, vitamin D deficiency has been proposed as a risk factor that could explain a significant proportion of these increases. Vitamin D deficiency has been documented in many countries worldwide, even in areas that are considered sun-replete.[9–11] This topic has been reviewed in this journal,[12] and this review will examine the recent studies, published between 2009 and 2011, that have investigated the role of vitamin D in childhood asthma and allergies.

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