Vitamin D and the Immune System

(cancers and autoimmune diseases)

Presently many claims are being made about vitamin D and its influence on cancers and the immune system. While these statements have some basis in fact, it is important to recognize that an overall understanding of vitamin D is far from being achieved.

What is known:

Our ancestors would have had significantly higher vitamin D levels than are currently observed in industrialized nations. Higher levels are observed in sun exposed populations today (about 55 ngm/ml of 25-OH D3).

Receptors for vitamin D and the enzymes to convent circulating 25-OH cholecalciferol to the active hormone are found in most human tissues - not just kidney, intestine and bone.

Marine organisms that do not have calcified skeletons make vitamin D – which is used for non-calcium/skeleton cellular regulatory processes. (It is interesting to note that osteoclasts, which participate in bone remodeling, are derived from the same human cell line as our immune cells.)

There is epidemiological and experimental evidence that many tumors and some autoimmune diseases are associated with low vitamin D levels or reduced sun exposure.  The problem with epidemiological evidence is that it can suggest associations.  Such information does not in and of itself prove causality.  Experimental laboratory data is beginning to shed light on the basic cellular control mechanisms in several tissues.

Making sense of the current data – which is far from consistent or conclusive – requires an in depth understanding of data analysis, cell physiology and immunology.  A comprehensive review of any of these topics is beyond the scope of this website or its author (who has a background in chemistry and medicine.) Vitamin D is very important in many aspects of human physiology. An understanding of its actions is very complex and far from complete. 

The recent Institute of Medicine review has a section with references and comments on this topic.

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