The purpose of this study is to determine the effect of vitamin D supplementation in Crohn's disease patients. Patients will be evaluated for increases in circulating vitamin D levels and effects on health benefits including improved bone markers, Crohn's disease activity scores, and inflammatory markers.

The incidence of autoimmune diseases like inflammatory bowel disease (IBD) has increased in developed countries over the last 50 years. We propose that decreased outdoor activity and increased pollution and diets that lack adequate vitamin D have combined to create large fluctuations in vitamin D status in developed countries and especially in populations that experience winter. Experimentally we've shown that changes in vitamin D status results in more severe forms of experimental IBD. In addition, active vitamin D (1,25(OH)2D3) completely blocks the development of experimental IBD. The vitamin D hypothesis proposes that vitamin D regulates the development and function of the immune system and that changes in vitamin D status affect the development of the resultant immune response and the development of diseases like IBD. Our hypothesis is that because of low dietary vitamin D intakes and malabsorption of many nutrients, Crohn's patients will have low circulating vitamin D levels that are detrimental for their health. We plan to give Crohn's patients 1000 IU of vitamin D/d and determine whether this dose is well tolerated, induces an increase in circulating vitamin D levels and has any additional health benefits (improved bone markers, Crohn's disease activity scores, inflammatory markers).

Inclusion Criteria:

• Patients 18-70 years of age with mild to moderate Crohn's disease who are not on active steroid treatment and who do not have ostomies.

Exclusion Criteria:

• Patients with ulcerative colitis or other bowel conditions which are not Crohn's.
• Patients with ostomies.
• Those currently using supplemental vitamin D in excess of the amount in one multivitamin per day.
• Regular tanning bed users.
• Persons who report more than moderate alcohol consumption ( > 1 drink/day for women > 2 for men).
• Pregnant or lactating women or women planning a pregnancy during the study time frame.
• Regular users of medications which may interfere with assessment of study outcomes .
• Those who cannot understand written or spoken English .
• Individuals under medical psychiatric care.

The period when adverse outcomes for each individual was 7 months.

No adverse events were noted in any of the patients.

The main limitation of the study was the lack of placebo control and the small size of the study.