Vitamin D and food allergies in children: A systematic review and meta-analysis

Background: Vitamin D insufficiency has been associated with immune dysfunction and linked to the epidemic of atopic diseases in the Western hemisphere, yet there are studies with conflicting results, and the risk has not been quantified uniformly across studies. Objective: To perform a systematic review and meta-analysis to evaluate and quantify if vitamin D deficiency is associated with the presence and persistence of food allergy. Methods: A systematic review was undertaken to assess for the association between food allergy and vitamin D status in children. Results: A total of 368 citations relevant to this systematic review were identified. In the whole review, 5105 children were included. We did not find a significant association between 25 hydroxy vitamin D (25(OH)D) status and risk of food allergy in children (odds ratio [OR] 1.35 [95% confidence interval {CI}, 0.79-2.29]; p = 0.27, I² = 58.3%). We conducted subgroup analyses based on different cutoffs of the 25(OH)D status (20 versus 30 ng/mL). Only one study used 30 ng/mL and found that children with <30 ng/mL were more likely to report food allergy than children with a 25(OH)D status of ≥30 ng/mL (OR 2.04 [95% CI, 1.02-4.04]; p = 0.04). Four studies compared children with a 25(OH)D status of >20 ng/mL to children with a 25(OH)D status of ≥20 ng/mL and found no significant differences (OR 1.18 [95% CI, 0.62-2.27]; p = 0.62, I² = 62.7%). Conclusion: Based on the studies analyzed, this systematic review did not identify a significant association between vitamin D status and food allergy. Interpretation of the included studies was limited by a lack of a standard definition for vitamin D deficiency and insufficient knowledge regarding the optimal vitamin D status needed to impact immune function. Longitudinal studies are warranted to assess if vitamin D might contribute to the development of food allergy.