Bone mineral density is decreased in inflammatory bowel diseases, which are intractable inflammation in the digestive tract. The causes of decreased bone mineral density are multifactorial including steroid use, insufficiency of nutritional intake, malabsorption in the gastrointestinal tract and activation of mucosal immune system. Insufficient levels of vitamins D and K are reported in patients with inflammatory bowel diseases and are also suggested to be involved in acceleration of intestinal inflammation.