Vitamin D

Overview

Vitamin D (calciferol; active form: calcitriol/1,25(OH)₂D₃) is a secosteroid hormone with profound immunomodulatory effects. The vitamin D receptor (VDR) is expressed on virtually all immune cells, and vitamin D deficiency is epidemiologically linked to autoimmune disease (MS, T1D, Hashimoto's, IBD), infection susceptibility, and depression. In the WikiBiome framework, vitamin D connects to the microbiome through antimicrobial peptide induction, Treg support, and direct modulation of gut barrier integrity.

Immune Effects

  • Antimicrobial peptides: Vitamin D induces cathelicidin (LL-37) and defensin production — direct antimicrobial effectors at mucosal surfaces.
  • Treg support: Vitamin D promotes Treg differentiation and IL-10 production, counterbalancing Th17 responses.
  • Th17 suppression: Calcitriol directly inhibits IL-17 production by Th17 cells.

Microbiome Interactions

  • Vitamin D supplementation alters gut microbiome composition — increases Bacteroidetes, modulates Firmicutes:Bacteroidetes ratio.
  • VDR expression in the gut epithelium regulates barrier integrity and antimicrobial peptide production.
  • Vitamin D + probiotic: Combined supplementation (vitamin D + Lactobacillus/Bifidobacterium) improved metabolic parameters in schizophrenia RCT [1].

Disease Relevance

  • MS: Low vitamin D is the strongest environmental risk factor; supplementation reduces relapse rate [2] [3].
  • T1D: Vitamin D deficiency associated with beta-cell autoimmunity [4].
  • Hashimoto's: Part of nutritional prevention strategy [5].
  • Schizophrenia: Vitamin D + probiotic RCT evidence [1].

Cross-References

References (5)

  1. Ghaderi A, Banafshe HR, Mirhosseini N et al. (2019). Clinical and Metabolic Response to Vitamin D Plus Probiotic in Schizophrenia Patients. BMC Psychiatry. doi:10.1186/s12888-019-2059-x
  2. Kathrine E. Attfield, Lise Torp Jensen, Max Kaufmann et al. (2022). The immunology of multiple sclerosis. Nature Reviews Immunology. doi:10.1038/s41577-022-00718-z
  3. Hoffman K, Doyle WJ, Schumacher SM et al. (2023). Gut Microbiome-Modulated Dietary Strategies in EAE and Multiple Sclerosis. Frontiers in Nutrition. doi:10.3389/fnut.2023.1146748
  4. Xinyun Bi, Fanghong Li, Shanshan Liu et al. (2017). Bi 2017 — Omega-3 Polyunsaturated Fatty Acids Ameliorate Type 1 Diabetes and Autoimmunity. Journal of Clinical Investigation. doi:10.1172/JCI87388
  5. Puszkarz I, Guty E, Stefaniak I et al. (2018). Role of Food and Nutrition in Pathogenesis and Prevention of Hashimoto's Thyroiditis. Journal of Education, Health and Sport. doi:10.5281/zenodo.1320419

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