The importance of vitamins D and K for the bone health and immune function in inflammatory bowel diseaseIijima, Hideki; Shinzaki, Shinichiro; Takehara, TetsuoCurrent Opinion in Clinical Nutrition & Metabolic Care: November 2012 - Volume 15 - Issue 6 - p 635–640 doi: 10.1097/MCO.0b013e328357f623 MICRONUTRIENTS: Edited by Gil Hardy and Henry Lukaski Abstract Author Information Purpose of review: This review summarizes the recent literature about the roles of vitamins D and K in bone metabolism and immunity-mediated inflammatory processes in inflammatory bowel diseases (IBDs). Recent findings: The levels of vitamins D and K are lower than normal in patients with IBD, especially in Crohn's disease. Although vitamins D and K are important for the maintenance of bone mineral density in non-IBD patients, an association between vitamins D or K and bone metabolism is not apparent in IBD patients. Recent studies showed that vitamins D and K are suggested to have immune-suppressive effects, both in animal models of colitis and human trials. In particular, vitamin D suppresses dendritic and T-cell functions by inhibiting the production of proinflammatory cytokines. Insufficiency of vitamin D is associated with the activated phenotype of IBD. Summary: Vitamins D and K potentially contribute to the maintenance of bone health in IBD, but this effect may be diminished by other factors such as steroid use, reduced exposure to sunlight, and inflammatory cytokines. Vitamin D and possibly vitamin K are suggested to be involved in the suppression of immune-mediated inflammation and modulation of disease activity. Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan Correspondence to Hideki Iijima, MD, PhD, Department of Gastroenterology and Hepatology, Osaka University Graduate School of Medicine, 2–2 Yamadaoka, Suita, Osaka 565–0871, Japan. Tel: +81 6 6879 3621; fax: +81 6 6879 3629; e-mail: firstname.lastname@example.org © 2012 Lippincott Williams & Wilkins, Inc.