What Can Early-Life Vitamin D Levels Tell Us About Allergy-Related Outcomes?

Vitamin D insufficiency can be like the slippery suspect in a network procedural: It’s probably up to no good on any number of counts, but pinning the crime on it with airtight evidence can still prove elusive.

A recent study in the Journal of Allergy & Clinical Immunology (JACI) sought to examine the associations between early-life vitamin D levels and the development of allergy-related outcomes. The study, which looked at a racially diverse population, also sought to differentiate the risk of vitamin D insufficiency with regard to race.Race is a consideration in the effect of vitamin D deficiency; earlier studies have shown that areas further away from the equator—and thus with a corresponding decrease in exposure to ultraviolet radiation, have been shown to have higher rates of childhood food allergy-related hospital admissions.

The interest in vitamin D research has been fueled by the relatively recent discovery that every tissue in the human body has vitamin D receptors. It is also widely accepted that vitamin D deficiency is widespread and is on the increase worldwide.Epidemiological studies have shown that low serum 25-hydroxyvitamin D levels are associated with a higher risk of upper and lower respiratory infections in children. A 2014 study published in Journal of Pediatrics suggested that infants with vitamin D deficiency are at an increased risk for food allergies over infants with vitamin D sufficiency. The study also found that the severity of atopic dermatitis may be related to vitamin D status.Other studies have suggested associations between childhood asthma, childhood atopy, and fetal lung and/or immune development, among others.

As yet, there is no consensus on what levels of vitamin D constitute an insufficiency or what doses of vitamin D should be used for supplementation. Further complicating the matter is the fact that some research on allergies has suggested that high levels of “the sunshine vitamin” may also contribute to the development of allergies.

The JACI study measured 25-hydroxyvitamin D (25[OH]D) levels in stored blood samples from pregnancy, cord blood, and blood taken at 2 years, then looked at incidence of eczema and increased allergen-specific immunoglobulin levels and physician diagnosis of asthma from ages 3 to 6. The study revealed that prenatal and cord blood 25(OH)D levels were associated with some allergy-related outcomes, with a general pattern indicating that children with higher 25(OH)D levels tend to have fewer allergy-related outcomes.Prenatal 25(OH)D levels were inversely associated with eczema, with a slightly stronger, though not statistically significant, association in white children.

Additional research on the impact of vitamin D deficiency is sorely needed.