This question needs to be resolved as medical practitioners determine patient treatment.  The complexity in the nomenclature of vitamin D has caused many errors.  The general thought in medical practice is that vitamins do nothing for illness and hormones are very effective.  Government medical guidelines are not reliable because of the conflicts of interest at the IOM.  There are several levels of people writing about vitamin D where people tend to get information.  Let’s take four examples: Level one – researchers, level two – medical activists and practicing doctors, level three – new discoverers of vitamin D as practicing doctors, and level four – people that have experienced healing with vitamin D as novices in the world of biochemistry.  We will ignore the government for now because they are more concerned about the economy than your health.

Your take away from this discussion is that you should never take or give vitamin D as anything other than high quality vitamin D3 as you may overcome the biological controls of the body and cause illness.  If you are an innocent health consumer then do not bother to read the rest of this post as it is technical and may confuse you.

Level One

Reinhold Vieth: A clinical researcher specializing in vitamin D nutrition on faculty at the University of Toronto Canada.  Why Vitamin D is not a Hormone   The importance of this paper written in 2005 is to help prevent practitioners from making mistakes in the nomenclature and administering the wrong compounds of vitamin D to patients.  If you are a doctor or other medical practitioner, then this is a must read.  Note that Vieth clearly states that vitamin D is a vitamin and then describes 25(OH)D as a prehormone.  He says that prohormone has no place in the vitamin D system.

Anthony W. Norman: A biomedical researcher and Distinguished Professor of Biochemistry & Biomedical Sciences, Emeritus at the University of California Riverside.  From Vitamin D to Hormone D: fundamentals of the vitamin D endocrine system for good health.  The importance of this paper is to help medical practitioners properly assist patients with vitamin D deficiency diseases.  This is a must read for medical practitioners. Written in 2008.  Dr. Norman is concerned that the new understandings of vitamin D are not translated to medical practice. Dr. Norman describes vitamin D as a prohormone produced photochemically in the skin from the prohormone 7-dehydrocholesterol and then goes on to describe the importance of its derivatives as hormones.  He then describes vitamin D3 as both a vitamin and a prohormone.  Note the distinction between vitamin D and vitamin D3.  This in essence groups the family of all “prohormone” vitamin D system molecules as vitamin D which includes more sterol derivative molecules than most practicing doctors can imagine. This probably provides more confusion than clarification to practitioners that are not expert biochemist, but read it anyway.

Level Two:

John J. Cannell, MD: Dr. Cannell is head of the  Vitamin D Council and has been a general practitioner and psychiatrist.  He launched his understanding of vitamin D in 2003 from a paper written by Reinhold Vieth.  Cannell describes vitamin D as a prohormone .  Note that he does not say vitamin D3.  I am guessing that he has adopted the nomenclature of Dr. Norman.  In his description of the vitamin D system he shows D2 and D3, pharmaceutical vitamin D, and vitamin D metabolites.

Level Three:

Stasha Gominak, MD:  A practicing neurologist in Tyler, Texas that discovered in 2009 the value of vitamin D3 and magnesium in treating neurological diseases, in particular sleep apnea.  Dr. Gominak describes vitamin D as a hormone  that is made in the skin.  She likes to use D hormone as it helps her understand the importance of the vitamin D system and that vitamin D hormone is made in our skin and not something that is obtained from outside her body.  She references the Vitamin D Council as her primary source of information.  She clearly states that vitamin D is not a vitamin.  This is somewhat dangerous because of the confusion that can be created between vitamin D3 and calcitriol with other doctors that she contacts or reads her info.

Level Four:

Mark Pegram, A Vitamin D Deficiency Survivor:  Yeah, that’s me, a health activist.  I will tell you now that this discussion is complex.  The importance of writing about vitamin D is to help you the innocent health consumer and medical practitioners to implement the new understandings of the vitamin D system in combination of other nutrients in which we are deficient.  It is never just one nutrient.  It is the combination of nutrients and minerals that allows our bodies to be healthy. The expression and control of our genome by the combination of nutrients is extremely important to health.  A proper combination of vitamins, minerals, proteins, fats, and carbohydrates is more important to prevent disease and to heal disease than most pharmaceuticals. Vitamin D3 is a vitamin and I believe the confusion is in the definitions.

Vitamin – One of a group of organic substances, other than proteins, carbohydrates, fats, minerals, and organic salts which are essential to normal metabolism, growth, and development of the body. (Taber’s Cyclopedic Medial Dictionary 13^th edition, yes I am an old guy as this was published in 1977)  Please note that in this definition it does not say that it is obtained outside of the body.  However, it later says in the definition that a vitamin is not formed in the body, but gives the exceptions of vitamin A, vitamin D, and vitamin K.

Hormone – A substance formed in an organ, gland, or part of the body and carried in the blood to another part of the body, stimulating it by chemical action to increase functional activity. (Taber’s Cyclopedic Medial Dictionary 13^th edition)

Prohormone – A prohormone is a substance that is a precursor to a hormone, usually having minimal hormonal effect by itself. The primary function of a prohormone is to enhance the strength of the hormone that already occurs in the body.  en.wikipedia.org/wiki/Prohormone

Prehormone – A prehormone is a biochemical substance secreted by glandular tissue and has minimal or no significant biological activity, but it is converted in peripheral tissues into an active hormone.

These definitions seem to agree with Dr. Vieth and have a historical content in the practice of research and medical practice.  I do not think our definitions should be changed and I think that Anthony W. Norman has tried to stick with that understanding.  The primary difference is in prohormone and prehormone which are relatively new terms of the last twenty years.  They are not listed in my 13^th edition of Taber’s.  The confusion is in the second sentence of the definition of prohormone – “enhance the strength of a hormone that already exists”. This seems to contradict the first statement as being a precursor.  I believe that Dr. Vieth has it correct in calling calcidiol, 25(OH)D,  a prehormone as it is not a hormone itself and is converted in most cells of the body to several steroid hormone forms of vitamin D, the new discovery by vitamin D researchers.

Now, if I could just figure out a way to get doctors to stop prescribing vitamin D2, vitamin D pharmaceuticals like dihydrotachysterol and Alfacalcidiol, and the metabolites; calcidiol(except in the case of liver failure), calcitriol (or Jeff and Geoff as Rich quipped in his comment on last post) then the benefits to health of D3 would be much more apparent and most likely without toxicity except for industrial accidents in manufacturing.  Of course, more important at this point is to get everyone replete in vitamin D3.  Again: Your take away from this discussion is that you should never take or give vitamin D as anything other than high quality vitamin D3 as you may overcome the biological controls of the body and cause illness. – Pandemic Survivor