It is beginning to look like Vitamin D is a central player in operation of our immune system. Numerous recent studies and clinical experiences suggest that vitamin D controls the production of an antimicrobial killer chemical known as cathelicidin. Our bodies encounter millions of bacteria and viruses every day, and our immune system is responsible for fending off these invaders on a continuing basis. It does so by first identifying the invaders as other that us, then sending a battery of cells to maim and kill them. Monocytes, a type of white blood cell, morph into macrophages when encountering a pathogen or other cells that need to be removed, and engulfs (eats) the bad guys. Then they use a battery of chemical weapons to destroy the invader, one of which is cathelicidin. Vitamin D has now been shown to ramp up the production of this killer molecule. Cathelicidin kills by punching holes in the external membrane of bacteria, fungi or viruses, destroying its internal integrity.
An article in the November 11, 2006 issue of Science News details a battery of studies that provide support for the link between vitamin D and immune function; in particular, expression of a gene that controls production of cathelicitin. It discusses the higher incidence of TB among Blacks than Whites in the northern latitudes, and that it correlate well with the know levels of vitamin D in the winter moths among these groups. Another segment of the article discusses experiments with skin infection and wound healing that ties sun exposure (and hence vitamin D levels and cathelicidin production in the skin) to enhanced resistance to infection and faster healing of wounds. Another part cites 5 studies since the 1930s linking reduced susceptibility to infectious disease to supplementation with cod liver oil, one of the best sources of vitamin D. A 1997 study showed a 13 times higher incidence of pneumonia among Ethiopian children with rickets (caused by low vitamin D) than in children without rickets.
Vitamin D3, the active form of the hormone in the human body, is converted to a prehormone through a cascade of reactions, circulates in the bloodstream and and then is converted to the hormone 1,25-D locally , as needed. In a cells nucleus, 1,25-D binds to a control switch next to the gene for cathelicidin and turns it on. This increase in cathelicidin production was first observed by geneticist John H. White of McGill University.
The synthesis of all these studies and observation will published in an upcoming issue of the journal Epidemiology and Infection by John J. Cannell, a psychiatrist at a psychiatric hospital in California. His interest began when a virulent flue epidemic hit one ward after another in his hospital in April, 2005, forcing quarantine of all the exposed wards but the ward he supervised. It hit him that maybe the seeming immunity was due to the high doses of vitamin D he was giving his patients because of measured deficiencies in much of its population. A few months later he read an article in FASEB Journal describing this increased production of cathelicidin due to vitamin D levels, and began to amass a library of related articles and studies to explore the link of vitamin D to immune function. He began discussions with other researchers of vitamin D and got them comparing notes, to the end that these collected results will be soon published, offering evidence of a strong correlation between vitamin D levels and immunity to bacterial, viral and fungal maladies.
It could be that your best shot against the much-tauted bird flu epidemic will be loading up on vitamin D; grandma would have loved this. What about testing this hypothesis against the regular old flu this season - that sounds like a good plan. The only way to know how you are doing in this regard is to have your blood levels checked regularly. The normal range is anywhere from 16 to 74ng/mL; you should tolerate nothing under 30, and shoot for maintaining close to 50ng/mL. Note that the vitamin D used to fortify milk is D2 not D3, and, according to Alan Inglis, M.D., milk is a very poor source of vitamin D and calcium for this reason. Probably the best source out there is high-quality cod liver oil. At the same time you get ample doses of EPA and DHA (the celebrated 'fish oil' omega-3 fatty acids) and vitamin A.
Good Living - Frank
