However, there is no explanation as to why Vitamin D
deficiency contributes to so many diseases. The primary focus of
this review is to develop the hypothesis that Vitamin D acts as a
custodian of phenotypic stability by maintaining the integrity of
cell signalling pathways. It will be argued that a decline in the
stability of signalling systems, such as the Ca2þ and redox pathways, may explain why Vitamin deficiency is such a major risk
factor in the development of so many diseases.