Vitamin D supplementation for the prevention of vitamin D deficiency after bariatric surgery: a systematic review and meta-analysis

Objective To evaluate the efficacy of vitamin D supplementation on the prevention of postoperative vitamin D deficiency. Methods PubMed, Embase, Web of Science, and Cochrane library were searched. Prospective studies evaluating the effects of vitamin D supplementation in patients who had undergone bariatric surgery were included. Meta-regression was performed to explore heterogeneity, and assess the relationship between dosage of vitamin D supplementation, study design, and prevalence of vitamin D depletion. Results Twelve studies enrolling 1285 patients met the inclusion criteria, and were included. Vitamin D supplementation was associated with significant improvements in 1-year Vitamin D depletion and 1-year 25-OHD level. A daily supplement of more than 800 IU vitamin D significantly reduced the prevalence of 1-year Vitamin D depletion, but the dosage of less than 800 IU did not. Significant decrease in prevalence of 1-year Vitamin D depletion was observed in randomized controlled trials (RCTs), but not in non-RCTs. For the 1-year 25-OHD level, significant elevation was found in the studies irrespective of the study design and dosage of vitamin D supplementation. Meta-regression showed that there was significant relationship between vitamin D depletion and study design, but not between vitamin D depletion and the dosage of vitamin D supplementation. Conclusion Vitamin D supplementation with a daily dosage of more than 800 IU is effective in preventing postoperative vitamin D deficiency and improving the 25-OHD level. However, the results should be interpreted cautiously since there was significant heterogeneity among the studies.