Tehran University of Medical Sciences Journal of Nutritional Sciences and Dietetics 6 1 2022 11 02 27 46 EN GLAREH KOOCHAKPOOR Maragheh University of Medical Sciences Sakineh Shabbidar Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences Zeynab Iraji Department of Statistics and Epidemiology, Faculty of Health, Tabriz University of Medical Sciences Firoozeh Hosseini-Esfahani Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Parvin Mirmiran Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences 2021 04 12 2021 07 15 An accurate understanding of B vitamin status in patients with Inflammatory Bowel Disease (IBD) can prevent controversial dietary advice; hence, the current study aimed to review the literature published on B vitamins status in patients with IBD systematically. An extensive literature search was conducted through search engines including PubMed, Scopus, and Google Scholar from Jan. 2000 to 26 April of 2020. The meta-analysis was performed using random effect measures.    Thirteen cross sectional and 19 case-control studies including 8492 participants were selected. Vitamin B12 deficiency was mostly observed (above 30%) in patients with Crohn disease (CD). Folate deficiency was mostly found in patients with CD (92%) and the ones with ulcerative colitis (UC) (94.2%). In several studies, the prevalence of vitamin B12 and B6 deficiency was greater in patients with CD than in the ones with UC. Based on meta-analysis results, there were no significant differences in the mean serum level of vitamin B12 between patients with IBD and controls. This review showed that the prevalence of B vitamins deficiency was higher in patients with UC than in the ones with CD, and folate deficiency was more common than other B vitamins deficiencies in patients with IBD. https://jnsd.tums.ac.ir/index.php/jnsd/article/view/322 https://jnsd.tums.ac.ir/index.php/jnsd/article/download/322/249