An estimated six million children have food allergies in the United States, with the prevalence continuing to rise over the past two decades. Currently, no treatment for latent food allergies exists; thus, methods focus on prevention or management.
Food allergies occur as a result of the immune system mistakenly attacking a harmless food protein, known as an allergen. The immune system then produces excessive amounts of an antibody called immunoglobulin E (IgE), which releases histamine and other chemicals to fight the allergen. Histamine causes an immediate inflammatory response.
Vitamin D possesses anti-inflammatory and immune strengthening properties. Therefore, researchers have hypothesized that vitamin D may be linked to food allergies. However, studies have produced conflicting results.
Researchers recently conducted a meta-analysis to assess the available research on vitamin D and food allergies. The meta-analysis included five studies, with a total of 5105 children.
The meta-analysis revealed no significant association exists between vitamin D status and risk of food allergy in children. They went on to conduct sub-analyses, assessing the results of studies that used different cutoffs of vitamin D status, specifically 20 versus 30 ng/ml.
Only one study used a cutoff of 30 ng/ml. This study found that children with levels below 30 ng/ml were more likely to have a food allergy than children with vitamin D levels above or equal to 30 ng/ml (p = 0.04). All four studies that compared the incidence of food allergies between children with vitamin D levels below 20 ng/ml to levels of 20 ng/ml or higher found no significant differences (p = 0.62).
The researchers call for larger studies before definitively declaring whether vitamin D plays a role in food allergies. They also stated that future studies need to use the vitamin D status needed for optimal immune health, which remains a topic of debate.
The study concluded,
“Until those studies are completed, we have insufficient evidence to support the role of vitamin D deficiency or insufficiency in sub-jects with established food allergy.”
The Vitamin D Council and the Endocrine Society advises everyone to keep his or her vitamin D level above 40 ng/ml. In the above analysis, there were too few children > 40 ng/ml in any of the five studies to do an analysis.
The mechanism of vitamin D’s anti-inflammatory actions are well known. Vitamin D increases a powerful anti-inflammatory cytokine (IL-10), which has a calming effect on the immune system. Vitamin D also increases the amount of T-regulatory cells (TREG). TREGs reduce levels of an inflammatory cytokine (IL-2). These two actions should reduce inflammation.
I suspect the reason they didn’t an association in this meta-analysis is because almost all the children were deficient. Thus, the researchers could not properly assess the benefits associated with healthy vitamin D levels.
Tovey, A. & Cannell, JJ. Research finds no relationship between food allergies and vitamin D status in children. The Vitamin D Council Blog & Newsletter, May 10, 2017.