Some researchers claim vitamin D is immunosuppressive; others argue it activates the immune system. Advocates for vitamin D supplementation insist that various forms of the “vitamin” can be protective against chronic disease, but longer-term studies have failed to confirm these findings [1]. Even among those who support widespread supplementation with the substance, there is wide acknowledgement that the understanding of vitamin D metabolism is “imprecise” [1].
L.R. Karhausen wrote, "Actually, there is no experience of causation: events do not wear their causal credentials on their faces." [2] In this Review, we discuss how the understanding of vitamin D metabolism in chronic disease may be approaching "black box epidemiology."[2]
We hope to show that although vitamin D is currently viewed in a beneficial light, explanations for how it provides a benefit are simplistic and imprecise.We will address liabilities of the disease/ deficiency model for vitamin D and summarize an alternative theory that, if valid, would necessitate rethinking systematic supplementation with vitamin D.
Contents
1. Introduction
2. Black box epidemiology
3. The Vitamin D Receptor and the vitamin D metabolites
4. Liabilities of the deficiency/disease model
5. Insights emerging from the molecular biology
5.1 Explanation for effects of vitamin D supplementation
6. 1,25-D and inflammatory disease
7. Conclusion
Take-home messages
References
