Is vitamin D deficiency a cause of CD symptoms?

Are Crohn's patients deficient in vitamin D because they have Crohn's Disease?  Or do they have Crohn's Disease because they are deficient in vitamin D?

"Hypovitaminosis D in Adults with Inflammatory Bowel Disease: Potential Role of Ethnicity" in Digestive Diseases and Sciences (2012)
"A significantly higher percentage of South Asians had hypovitaminosis D when compared to Caucasians. Disease severity trended towards an inverse relationship with vitamin D status in all South Asian and Caucasian CD patients, although most patients in this study had only mild to moderate disease. We suggest that vitamin D supplementation should be considered in all adult IBD patients."


"Vitamin D Deficiency in Patients With Inflammatory Bowel Disease" in JPEN (2011)
"Vitamin D deficiency is common in IBD and is independently associated with lower HRQOL and greater disease activity in CD. There is a need for prospective studies to assess this correlation and examine the impact of vitamin D supplementation on disease course."


"High Prevalence of Vitamin D Inadequacy and Implications for Health" in Mayo Clinic Proceedings (2006)
"Supplemental doses of vitamin D and sensible sun exposure could prevent deficiency in most of the general population. The purposes of this article are to examine the prevalence of vitamin D inadequacy and to review the potential implications for skeletal and extraskeletal health. "

"Low wintertime vitamin D levels in a sample of healthy young adults of diverse ancestry living in the Toronto area: associations with vitamin D intake and skin pigmentation" in BMC Public Health (2008)
Conclusions:  "Our study suggests that the prevalence of low vitamin D levels in young adults living in Canada (Southern Ontario) may be higher than previously described. Our sample included individuals of diverse ancestry, and as such provides a better representation of the multi-ethnic composition of Canadian metropolitan areas than previous studies. Our research also indicates that there are differences in serum 25(OH)D levels and vitamin D intake between population groups and that the currently Recommended Adequate Intake of vitamin D (RAI = 200 IU/day) may not be met by a large proportion of the young adults. Vitamin D intake was particularly low amongst those young Canadians at greatest risk of vitamin D insufficiency. Furthermore, our study suggests that the current vitamin D recommendations in the US and Canada (200 IU/day) are insufficient to ensure optimal circulating 25(OH)D levels, which are defined by most vitamin D experts as 75 nmol/L."

"Vitamin D: a D-Lightful health perspective" in Nutrition Reviews (2008)
TREATMENT FOR VITAMIN D DEFICIENCY
"Vitamin D deficiency requires immediate attention and aggressive vitamin D replacement.13,30 When a person is vitamin D deficient, simply giving them what is now thought to be the required amount of vitamin D3, i.e., 1000 IU/day, will only satisfy what the body requires and will gradually increase the blood levels of 25(OH)D. To quickly correct vitamin D deficiency, 50,000 IU of vitamin D2 once a week for 8 weeks is often effective. In most patients, blood levels of 25(OH)D will rise on average by 100%. For those who are severely deficient, an additional 8-week course of 50,000 IU of vitamin D2 is recommended. Since the individual presented with vitamin D deficiency, it's likely that they will become vitamin D deficient again unless they take an adequate amount of vitamin D either as 1000 IU of vitamin D3/d or 50,000 IU of vitamin D twice a month. An alternative strategy that was found to be effective was to give 100,000 IU of vitamin D3 every 3 months."