Assessing the Effect of Vitamin D Insufficiency in African American Patients with Inflammatory Bowel Disease

Previous research has shown that vitamin D may play an immunoregulatory role in inflammatory bowel disease (IBD) and that there may be a connection between lower levels of vitamin D and IBD in Caucasian patients. Researchers from the Johns Hopkins Genetics Research Center of the NIDDK IBD Genetics Consortium examined this connection in a cohort of African American patients with IBD and a control group of those patients’ African American spouses and friends without IBD.

Diagnosis of Crohn’s disease, ulcerative colitis, and/or indeterminate colitis was confirmed by review of medical records. There were 89 patients with IBD included in the analysis and 90 controls with a similar mean age of 42 years. The case group included 57 patients with Crohn’s disease, 24 with ulcerative colitis, and 5 with indeterminate colitis.

After adjusting for age and sex, the researchers reported no significant difference in mean vitamin D levels between the case group (19.19 +/- 9.73 ng/ml ) and the controls (18.6 +/- 8.40 ng/ml). In the case group, the patients diagnosed with indeterminate colitis had lower mean vitamin D levels (14.5 +/- 4.8 ng/ml) than the Crohn’s (19.6 +/- 10.4 ng/ml) and the ulcerative colitis (19.0 +/- 8.8 ng.ml) groups.

They also reported no significant difference in vitamin D deficient (defined as vitamin D levels less than 20 ng/ml) or vitamin D insufficient (defined as vitamin D levels less than 30 ng/ml) between the two groups.

The researchers reported that increased age “showed the only trend worth noting for greater deficiency” of vitamin D, but it did not rise to the level of significance. Patients with ileal disease had slightly lower odds of being vitamin D deficient compared to patients with non-ileal disease.

They also noted a “small” trend toward lower vitamin D levels in patients with Crohn’s disease with structuring and penetrating disease compared to patients with non-stricturing, non-penetrating disease.

Female patients were more than twice as likely to be vitamin D deficient, but this was not statistically significant and only led to small differences in overall vitamin D levels.

Based on these data the authors concluded that African American patients are “overwhelmingly” vitamin D deficient; more than 50% of the current cohort was vitamin D deficient. African American patients with IBD do not have lower levels of vitamin D compared to healthy patients. They conjectured that this lack of difference may be secondary to environmental effects on vitamin D levels in this “highly matched cohort of spouses and friends of the cases,” or possibly from unknown supplementation.

Although they found trends for lower vitamin D levels with “male sex, disease location, and behavior” in Crohn’s disease, none of them were statistically significant.