Allergies are a common condition for both children and adults. It is an inflammatory condition involving an immunoglobulin E (IgE)-mediated immune response. Vitamin D and the gut microbiota play roles in overall health, including normal immune function. Research demonstrates that vitamin D deficiency may influence the microbiota and immune function and their connection with an allergic response.

The microbiota plays an important role in overall health, including the support of immune function. The presence of microbes requires the immune system to find a balance between triggering an appropriate response to commensal bacteria and fighting against potential pathogens. Imbalances in the skin, gut, and respiratory microbiota are associated with allergic diseases, including atopic dermatitis, asthma, allergic rhinitis, and food allergies.

Vitamin D plays many roles in the body, including the support of immune function. Vitamin D receptors are expressed in a variety of tissues and on many immune cells. It modulates the immune response, including decreasing neutrophils, eosinophils, IgE production, mast cell differentiation, inflammatory cytokines, increasing Treg cells, and interleukin-10 synthesis and expression. 

Additionally, vitamin D may play a role in regulating the gut microbiome. This may occur by supporting host-microbial interactions in the small intestine and colon, playing roles in proliferation, differentiation, intestinal permeability, immunity, and susceptibility to pathogenic infection. Metabolites from the gut microbiomes may regulate the expression of vitamin D receptors. Vitamin D supplementation has been shown to potentially promote a healthy microbial composition.*

Healthy vitamin D levels may be one avenue for supporting immune function, which includes a healthy response to allergens.* One study on children with allergic diseases found that patients with allergic disease were more likely to have vitamin D deficiency compared to controls. Those with mild allergic disease were more likely to have higher vitamin D concentrations compared to those with more severe clinical symptoms. One systematic review and meta-analysis found that patients with atopic dermatitis were at high risk for lower serum levels of 25(OH)D. The reviewers also found that supplementing with 1,600 IU of vitamin D daily led to a clinically meaningful reduction in the severity of atopic dermatitis. Another meta-analysis found that vitamin D supplementation had potential benefits for asthma. Supplementation reduced the rate of asthma exacerbation, especially in those with a deficiency, and had a positive effect on pulmonary function.

The immune system and its response to allergens are complex with many factors influencing the response. Vitamin D may have one role to play in supporting a healthy immune response to allergies, possibly due to its effect on both the immune system and the gut microbiota.* More research will further detail the relationship between vitamin D, the gut microbiota, and allergic diseases.

By Kendra Whitmire, MS, CNS