**6.4 Malnutrition**

Nutritional deficits linked to inflammatory bowel disorders have been mentioned as additional pathogenic pathways causing low bone mineral density. There have been reports of calcium insufficiency in Crohn's disease due to either inadequate intake or poor intestinal absorption [51–53].

Patients with ulcerative colitis and/or Crohn's disease have been found to have more vitamin D deficiencies compared to the control healthy population reference range. Elevated levels of bone turnover markers coexist with decreased vitamin D level in Crohn's disease patients compared to controls. In general, patients with inflammatory bowel disease have lower vitamin D status for a number of reasons, including [54]: lack of vitamin D lowers calcium levels and triggers secondary hyperparathyroidism, which in turn promotes osteoclastogenesis, increases bone resorption, and causes osteopenia and osteoporosis [55].


Vitamin K insufficiency may potentially have a role in osteopenia related to IBD. Because of ileopathy, some patients may absorb this fat-soluble vitamin. However,

the discrepancies in vitamin K status between patients with ulcerative colitis and Crohn's disease may result from changed bacterial flora that produces less vitamin K. Additionally, it is likely that antibiotics, which are frequently used to treat inflammatory bowel disease patients, could eradicate flora that produces vitamin K [54, 56].
