Tag Archives: vitamin D deficiency

Why Adding Vitamin D May Not Help IBD

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Despite all of the accolades that vitamin D has received, the fact that low vitamin D is associated with worse outcomes, in a number of disease states, does not prove causality. A recent article indicates that vitamin D is likely more of a marker of disease activity than a mediator of disease activity in inflammatory bowel disease (IBD), and specifically Crohn’s disease (CD) (Inflamm Bowel Dis 2014; 20: 856-60).

Background: Binding sites for the vitamin D receptor (VDR) have been “identified in genes associated with CD, and vitamin D has been shown to enhance the production of interleukin-10 (IL-10) and induction of regulatory T-cells.”

Design:The authors prospectively collected samples of 37 CD patients; the mean age in those with active disease (n=20) was 34 years and it was 30 years in those with inactive disease. In 8 patients with active disease, vitamin D levels were measured at the time of active inflammation (day 0) and at 14 days after receiving infliximab (day 14).

  • Key finding in these 8 patients: Vitamin D (25-OH) was 23 ng/mL on day 0 and 40 ng/mL 2 weeks later.  Only 1 of these 8 patients was taking a vitamin D supplement.
  • Key finding in the entire cohort: in the active disease group mean vitamin D level was 27 ng/mL compared with 38 ng/mL in those in remission (P=0.02).

Take-home point: There is an inverse relationship between vitamin D levels and disease activity.  However, the early increases in vitamin D levels with clinical response to anti-TNF therapy suggests that a major mechanism of vitamin D deficiency is related to the burden of systemic inflammation.  Hence, repeat testing when patients are in remission may obviate the need for vitamin D supplementation in many patients.

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Explaining the Vitamin D Paradox

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For a long time, there has not been a satisfying explanation for the fact that blacks have higher bone mineral density but lower 25-hydroxy-vitamin D levels than whites.  New research (NEJM 2013; 369: 1991-2000, editorial 22047-48) helps explain this paradox.

This study examined a community cohort of 2085 individuals in the “Healthy Aging in Neighborhoods of Diversity across the Life Span” study.

Key Findings:

  • Blacks had higher bone mineral density and lower 25-hydroxy-vitamin D levels than whites
  • The calculated bioavailable levels of 25-hydroxy-vitamin D were similar to whites.

The editorial notes that the similar bioavailability is due to differences in the vitamin D-binding protein (aka GC-globulin).  “GC1F is the most abundant form in persons of African ancestry whereas GC1S is most abundant in European populations.”  Thus, it has been hypothesized that the vitamin D-binding protein in blacks has “increased affinity for vitamin D3, and thus able to transport vitamin D3 more efficiently from the skin to the liver for its metabolism to 25-hydroxy-vitamin D.”

Bottomline: This research in vitamin D metabolism may impact on how we determine vitamin D deficiency.  The measurement of vitamin D-binding protein may need to be incorporated into the assessment.

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Vitamin D deficiency and metabolism in pediatric Crohn’s disease

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As noted in previous blog posts (see links below), vitamin D has received a great deal of attention with a number of chronic diseases.  In this latest study from CHOP, the incidence and mechanisms of vitamin D deficiency in pediatric Crohn’s disease are explored (Inflamm Bowel Dis 2013; 19: 45-33).

At diagnosis (2002-2005), Crohn’s disease (CD) participants (n=78) had their serum vitamin D assays and parathyroid hormone (PTH) levels checked.  Then, these values were sequentially followed at 6 months, 12 months, and a median of 43 months later (n=52). The average age of the CD patients was 12.7 years.

Key findings:

  • 42% of CD participants were 25-OH D deficient (<20 ng/mL) with an odds ratio of 2.1 compared with controls.
  • Among patients with 25-OH D <30 ng/mL, CD patients had a lower PTH than controls.
  • At final visit, 3% remained 25-OH D deficient and PTH levels corrected.
  • Risk factors, besides CD, for vitamin D deficiency: black race (OR 10.4), visit in winter (OR 2.4), age 12 to <15 (OR 2.7), age >15 (OR 3.2).  Greater disease activity was associated with lower vitamin D levels at baseline.

Implications of this study:

  1. Vitamin D deficiency normally causes secondary hyperparathyroidism.  With newly-diagnosed CD, there was a relative hypoparathyroidism that resolved with therapy.  “It is conceivable that proinflammatory cytokines associated with CD …prevent an appropriate PTH response.”
  2. The authors state that ‘vitamin D deficiency likely contributes to the pathogenesis of CD through effects on T and B lymphocyte, macrophage, and dendritic cell regulation.”  Correcting vitamin D deficiency may improve CD treatment response in addition to potential improvements in bone health.

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