Introduction: The literature shows a bimodal incidence of Crohn's disease in relation to age, with peaks from 15-40 and from 50-80 years and more women have Crohn's disease than men. Clinical studies have shown a direct correlation of vitamin D deficiency with Crohn's disease. Objective: Using a systematic review, the objective of this study was to identify the main correlations and outcomes of clinical studies about vitamin D in Crohn's disease. Methods: Following the rules for systematic reviews (PRISMA), the key search terms used were Crohn's disease, vitamin D, clinical studies, immunotherapy and quality of life. After applying exclusion criteria, 117 articles were included and discussed in this study. Conclusion: The prevalence of low serum vitamin D levels has been demonstrated in patients suffering from Crohn's disease. However, further studies that are more comprehensive are still needed, in particular investigations that aim to evaluate the effects of serum vitamin D levels on clinical treatment and the effects of vitamin D supplementation on disease activity and mucosal healing. Thus, it may be possible to optimize the treatment of Crohn's disease patients thereby improving their quality of life.

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