IBD and Vitamin D: Exploring the Link The relationship may be bidirectional

Some studies have suggested that individuals with Crohn's disease or ulcerative colitis have low levels of vitamin D, with up to 60% to 70% of patients possibly having insufficiency and half of those being deficient. Those numbers are influenced by other factors, however, such as the location and the season of the year when the vitamin D levels are measured. Several studies have shown geographic variation in the incidence of IBD. For instance, in the prospective Nurses' Health Studies I and II, 175,912 women reported their area of residence in 1992. During more than three million person-years of follow-up, the incidence of both Crohn's disease and ulcerative colitis increased with higher latitude and less ultraviolet exposure. Compared with women living in northern areas of the U.S., those residing in the south had an adjusted hazard ratio of 0.48 (95% CI 0.30-0.77) for Crohn's disease and 0.62 (95% CI 0.42-0.90) for ulcerative colitis (P<0.01). https://www.medpagetoday.com/reading-room/aga/lower-gi/65873?xid=nl_mpt_DHE_2017-06-09&eun=g721819d0r&pos=3