D-fending against dermatitis

Introduction

Atopic dermatitis (AD), also known as eczema, is a skin condition that causes dry, itchy red skin. Scratching can result in inflammation and injury to the epidermis, the top-most layer of the skin. The prevalence^[1] of this condition has been increasing in both children and adults over the past several decades. It can affect up to 20% of children, though symptoms usually resolve for most prior to adulthood. One trial showed that people who get more sun exposure^[2] have a lower incidence of AD, and that symptoms are generally more severe in winter when sunlight exposure is lower, although most people tend to have an increase in dry itchy skin during the winter months when the skin is exposed to colder and drier air.

There has been some evidence^[3] to show that a higher intake of certain vitamins, including vitamins D and E, may improve the symptoms of AD. Several different mechanisms of action have been suggested, some of which are shown in Figure 1. One is that vitamin D can increase the production^[4] of antibacterial peptides and barrier formation molecules on the surface of the skin, which strengthens and prevents infection of the skin surface. There is also evidence that vitamin D supports^[5] the production of a number of immune system molecules related to the reduction of inflammation.

While several individual studies have been completed in various populations to assess the effects of vitamin D supplementation on AD, the results of studies have been somewhat inconsistent, and no meta-analysis to date has been conducted to evaluate the overall trend of these studies. The authors set out to assess the relevant literature on AD and vitamin D, and conduct a meta-analysis of clinical trials on this topic.

Atopic dermatitis, or eczema, is a skin disease that has been increasing in prevalence worldwide. Both oral intake of vitamin D and increased sun exposure have been associated with improvements in the symptoms of AD.

Figure 1: Vitamin D in atopic dermatitis: antimicrobials, barrier formation, and inflammation

Who and what was studied?

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