Association between 25(OH)D Level, Ultraviolet Exposure, Geographical Location, and Inflammatory Bowel Disease Activity: A Systematic Review and Meta-Analysis

Abstract

BackgroundThere is no consensus on the vitamin D levels and inflammatory bowel disease (IBD).AimTo conduct a systematic review and meta-analysis to analyze the relationship between IBD and 25(OH)D, sun exposure, and latitude, and to determine whether vitamin D deficiency affects the severity of IBD.MethodsWe searched the PubMed, EBSCO, and ClinicalTrials.gov databases to identify all studies that assessed the association between 25(OH)D, sun exposure, latitude, and IBD through November 1, 2014, without language restrictions. Studies that compared 25(OH)D levels between IBD patients and controls were selected for inclusion in the meta-analysis. We calculated pooled standardized mean differences (SMDs) and odds ratios (ORs).ResultsThirteen case-control studies investigating CD and 25(OH)D levels were included, and eight studies part of above studies also investigated the relationship between UC and 25(OH)D. Both CD patients (SMD: 0.26 nmol/L, 95% confidence interval [CI]: 0.09–0.42 nmol/L) and UC patients (SMD: 0.5 nmol/L, 95% CI: 0.15–0.85 nmol/L) had lower levels of 25(OH)D than controls. In addition, CD patients and UC patients were 1.95 times (OR, 1.95; 95% CI, 1.48–2.57) and 2.02 times (OR, 2.02; 95% CI, 1.13–3.60) more likely to be 25(OH)D deficient than controls. We also included 10 studies investigating the relationship between CD activity and vitamin D. Results showed that patients with active CD (CD Activity Index≥150) were more likely to have low vitamin D levels. In addition, whether low sun exposure and high latitude were related to a high morbidity of CD need to be provided more evidence.ConclusionOur study shows that IBD patients have lower vitamin D levels. For active CD patients, vitamin D levels were low. These findings suggest that vitamin D may play an important role in the development of IBD, although a direct association could not be determined in our study.

Vitamin D Status and Efficacy of Vitamin D Supplementation in Atopic Dermatitis: A Systematic Review and Meta-Analysis

“…Thus, we assumed that the included AD patients in this meta-analysis probably had vitamin D deficiency and similar 25(OH)D levels. Second, we did not adjust for potential confounding factors of the serum 25(OH)D level in the selected populations, such as altitude, latitude, sun exposure, seasonal variation, level of outdoor activities, and dietary vitamin D intake [36]. Third, significant interstudy heterogeneity was present, which can be partially attributed to the confounding factors.…”

Low Sun Exposure and Vitamin D Deficiency as Risk Factors for Inflammatory Bowel Disease, With a Focus on Childhood Onset

“…Two recent systematic reviews and meta‐analyses of observational studies showed that, in adults, patients with IBD had significantly lower 25OHD levels and were more likely to be vitamin D‐deficient than controls (without IBD) . In both studies, subgroup analysis showed that, although pediatric patients with IBD also had lower 25OHD levels (and higher prevalence of vitamin D deficiency) than non‐IBD controls, this difference was not statistically significant.…”

The role of UVR and vitamin D on T cells and inflammatory bowel disease

“…A recent systematic review and meta-analysis was done to determine the association of 25(OH)D levels, UVR exposure, geography and IBD. 25 The conclusions of the study were that both Crohn’s disease and ulcerative colitis patients had lower levels of vitamin D and lower levels of 25(OH)D were associated with higher Crohn’s disease activity indexes (CDAI; there were too few studies to evaluate ulcerative colitis). 25 However, because of a lack of adequate data no correlations could be made between latitude, geography and IBD.…”

“…25 However, because of a lack of adequate data no correlations could be made between latitude, geography and IBD. 25 …”