Shi, Shanzhen, Jiaxing Feng, Lixiang Zhou, Yu Li, and Huaxiu Shi. “Risk Factors for Vitamin D Deficiency in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis”. Turkish Journal of Gastroenterology 32, no. 6 (January 6, 2021): 508–518. Accessed January 1, 2026. https://www.turkjgastroenterol.org/index.php/tjg/article/view/3742.