in the majority of studies, but evidence on whether supplementation can improve symptoms of the condition was inconsistent.
The data on the effect of vitamin D supplementation on AD severity “suggested potential benefit but were conflicting,” concluded Christina M. Huang, MD, of Queen’s University, Kingston, Ontario, and her coinvestigators from the department of dermatology, Hospital for Sick Children, Toronto. They reported the results of their systematic review of 21 studies published between 2008 and 2017, which included quantitative data on serum vitamin D levels or vitamin D supplementation and AD severity in patients aged 18 years or younger, in Pediatrics.
In the review, 16 studies explored the relationship between serum vitamin D status and disease severity (one was a randomized controlled trial; the rest were cohort, cross-sectional, or case control studies) in 1,847 children (average age, 5.6 years). Disease severity was measured with the SCORing Atopic Dermatitis (SCORAD) system. In 10 of the 16 studies, there was a significant inverse association between vitamin D levels and AD severity.
The studies that supported this association generally had larger sample sizes, which, the authors pointed out, suggested they were of higher quality and more reliable. However, the randomized controlled study of 89 children did not find a correlation, although in the study, vitamin D level and AD severity was a secondary outcome.
The randomized controlled trial of vitamin D supplementation used lower SCORAD cut-offs for the different severities of AD, which complicated interpretation the results, “as it may indicate that the severities reported in these articles were exaggerated as compared to other studies,” they wrote.
Six studies – four randomized controlled trials (including the study that was among the 16 studies on vitamin D and severity) and two cohort studies – with 354 participants (average age, 6.8 years) looked at the effects of oral vitamin D supplementation on the severity of AD, although dosage and duration of use varied across the studies. In four of the six studies, there were significant improvement in AD in patients given supplements, but the data were “conflicting,” partly because the largest study showing benefit used a different measure of disease severity, the Eczema Area and Severity Index (EASI), not SCORAD. “The inconsistency of tools used to measure outcomes makes it difficult to compare and understand results,” so the effects of vitamin D supplementation “are controversial and should be interpreted with caution, as certain patient populations may benefit more than others,” the authors wrote.
They also drew attention to previous research suggesting that vitamin D supplementation in the first year of life might actually increase the risk of AD in children. “Therefore, although there is a growing body of evidence supporting the beneficial effects of VD [vitamin D] supplementation, the age at which supplementation is given should be considered carefully.” The authors added that the inconclusive findings “may have been due to confounding factors that were not accounted for, such as age, season, latitude, dose, and duration. It is also possible that the lack of a true effect of VD may be contributing to the inconsistent results. Future large‐scale RCTs with consideration of these factors are needed.”
Funding and conflict of interest disclosures were not included in the study.
SOURCE: Huang C et al. Pediatr Dermatol. 2018;35: 754-60. doi: 10.1111/pde.13639.