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In the last post, we talked about the new report on vitamin D and cancer from the International Agency for Research into Cancer (IARC). In this one, we'll summarise what the report has to say on the balance between getting enough vitamin D through sun exposure and reducing the risk of skin cancer by being SunSmart. IARC calls for more trials to really pin down the effects of vitamin D supplements - either positive or negative - depending on how much vitamin D people already have in their system. Until then, they feel that there is no solid basis for changing any existing recommendations about vitamin D.

Professor Robert P. Heaney's talk about vitamin D deficiency and what actions should be taken

Paradigms and Paradoxes Last month Dr. Armin Zittermann of Ruhr University, Germany, published the best vitamin D paper of the month. He reviewed the mounting evidence that vitamin D deficiency is a major cause of heart disease. Zittermann A, Schleithoff SS, Koerfer R. Putting cardiovascular disease and vitamin D insufficiency into perspective. Br J Nutr. 2005 Oct;94(4):483-92. Before we start, let's talk about paradigms and paradoxes. A paradigm is a set of assumptions, concepts, and practices that constitutes a way of viewing reality. The current paradigm is that heart disease is caused by a combination of genetics, hypertension, diabetes, cholesterol, smoking, obesity, inactivity, and diet. A paradox is a fact that contradicts the paradigm.

I stumbled on one of the growing number of local media stories on the power of vitamin D. \nIn one story, a purported "expert" was talking about the benefits of "high-dose" vitamin D, meaning up to 1000, even 2000 units per day. \nI regard this as high-dose---for an infant. \nJudging by my experiences, now numbering well over 1000 patients over three years time, I'd regard this dose range not as "high dose," nor moderate dose, perhaps not even low dose. I'd regard it as barely adequate.

"I discussed in my last post how Dr Vieth has a model of tissue 1,25(OH)2D synthesis and degradation in which the level of active substance is pretty well independent of blood vitamin D level, provided the level is either rising or stable. I think it is also worth pointing out that he is talking, hypothetically, about tissue 1,25(OH)2D, not plasma level... As we know, almost nothing is known about tissue 1,25(OH)2D control. By Vieth's hypothesis tissue 1,25(OH)2D is OK so long as there is at least SOME vitamin D present in plasma and the level dose not vary too much. Obviously there is a level below which you can have as much of the enzyme for converting vitamin D to the active form as you like, if there is no vitamin D in your blood you can't make any 1,25(OH)2D in your tissues, or in your kidneys for export to your blood to control calcium levels. At the lower extremes we have rickets and osteomalacia. These are clear cut, unarguable markers of vitamin D deficiency, in the absence of confounding factors (there are a few)."