Impact of vitamin D supplementation on markers of bone turnover: Systematic review and meta-analysis of randomised controlled trials.

AIM: The effects of vitamin D administration on bone turnover markers (BTMs) in adults are controversial. Thus, we carried out a meta-analysis of available randomised controlled trials (RCTs) to examine the impact of vitamin D supplementation on BTMs. METHODS: To identify relevant RCTs, we searched the PubMed/MEDLINE, Web of Science, Scopus, Cochrane Library and Embase databases for manuscripts published up to July 2022. The present study was conducted in agreement with the PRISMA guidelines. Weighed mean difference (WMD) and 95% confidence intervals (CI) were used to calculate the magnitude of the effect of the intervention. RESULTS: A total of 42 RCTs were included in the meta-analysis. The age of the participants enrolled in the RCTs ranged from 19.4 to 84 years. The pooled results depicted a decrease in deoxypyridinoline (DPD) concentrations (WMD: -1.58 nmol/mmol, 95% CI: -2.55, -.61, p = .001) following vitamin D supplementation. In addition, subgroup analyses demonstrated that vitamin D administration notably reduced procollagen type I N-terminal propeptide (PINP) levels in individuals aged >50 years and led to a pronounced decrease in alkaline phosphatase (ALP) values when the intervention lasted >12 weeks. No significant effect was observed on other BTMs, for example, collagen type 1 cross-linked C-telopeptide (CTX) and osteocalcin (OC) levels. CONCLUSION: Vitamin D administration decreases DPD, PINP and ALP levels, indicating a reduced bone turnover following the intervention. Other BTMs, for example, CTX or OC values, were not affected by vitamin D prescription. Vitamin D supplementation may exert a positive effect on some important BTMs.

The association between vitamin D status and inflammatory bowel disease among children and adolescents: A systematic review and meta-analysis.

Aim: Vitamin D deficiency is very common among children with IBD. Since there are conflicting results regarding the association of vitamin D with IBD, we conducted this systematic review to confirm the association of vitamin D with IBD. Methods: We conducted a systematic search in Scopus, Cochrane Library, Web of Science, PubMed, and Google Scholar to find relevant studies. Articles with cross-sectional and case-control designs that reported the association between vitamin D and IBD among children were included. Results: Eventually, 9 studies (with 16 effect sizes) reported the mean and SD or the median and the interquartile range of serum vitamin D levels in both subjects with IBD and control subjects. The random effects meta-analysis revealed that subjects with IBD had -1.159 ng/ml (95% CI: -2.783, 0.464) lower serum vitamin D concentrations compared with their healthy counterparts, but this difference was not significant. A total of 14 studies (with 18 effect sizes) with 2,602 participants provided information for the prevalence of vitamin D deficiency or insufficiency in patients with IBD as 44% (95% CI: 0.34-0.54) with significant heterogeneity noted among studies (p < 0.001; I2 = 97.31%). Conclusion: This systematic and meta-analysis study revealed that vitamin D deficiency was associated with IBD. Longitudinal studies should be conducted in the future to confirm our findings. Large randomized controlled trials assessing the doses of supplementation of vitamin D would provide a better understanding of the association between vitamin D and IBD.