Prevalence and associated factors of vitamin D deficiency after Roux-en-Y gastric bypass: a systematic review and meta-analysis

Objects:To estimate the prevalence and associated factors of vitamin D deficiency (VDD) after Roux-en-Y gastric bypass (RYGB).Methods:PubMed, EMBASE, and CENTRAL were searched for relevant records from inception to 17 March 2023, using search terms: vitamin D, vitamin D3, vitamin D deficiency, hypovitaminosis D, gastric bypass, and RYGB. Studies were eligible for inclusion if they provided related data on VDD prevalence after RYGB.Results:Of the 1119 screened studies, 72 studies involving 7688 individuals were enrolled in the final analysis. The prevalence estimates of VDD after RYGB were 42%. Subgroup analyses suggested the pooled prevalence of postoperative VDD was 35% for follow-up duration less than or equal to 1 year, 43% for greater than 1 and less than or equal to 5 years, and 54% for greater than 5 years. Meta-regression showed that VDD prevalence was positively correlated with follow-up time. Also, the prevalence was higher in studies with inadequate vitamin D supplementation than in those with adequate supplementation and in Asia population than in those from South America, Europe, and North America. Other factors associated with high VDD prevalence after RYGB included high presurgical VDD prevalence, noncompliant patients, and black populations. No significant association existed between VDD and alimentary length.Conclusion:VDD presented a high prevalence in patients following RYGB. It occurred more frequently with longer postoperative follow-up time. Population-specific vitamin D supplementation measures, targeted treatment for presurgical VDD, improved patient compliance, and periodical follow-ups were necessary to reduce VDD and other adverse outcomes.