The importance of vitamins D and K for the bone health and immune function in inflammatory bowel disease.
OBJECTIVE
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).


RESULTS
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.


CONCLUSIONS
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. hiijima@gh.med.osaka-u.ac.jp
Hideki
H
Iijima
Shinichiro
S
Shinzaki
Tetsuo
T
Takehara
D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D002986:Clinical Trials as Topic; D016207:Cytokines / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007155:Immunologic Factors / Q000378:metabolism; D007249:Inflammation / Q000503:physiopathology; D015212:Inflammatory Bowel Diseases / Q000276:immunology* / Q000503:physiopathology; D013472:Sunlight; D013601:T-Lymphocytes / Q000378:metabolism; D014807:Vitamin D / Q000502:physiology*; D014812:Vitamin K / Q000502:physiology*
D016207:Cytokines; D007155:Immunologic Factors; D014812:Vitamin K; D014807:Vitamin D