The basics of Vitamin D – what is it and what does your body do with it?

By: Andrew Stewart                                                                                                      Published 07/23/13

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Let’s start off first by recognizing that “Vitamin D” isn’t necessarily one unique substance that our bodies need. It’s really an umbrella term which describes a group of molecules of similar structure.

For example, Vitamin D3 (Cholecalciferol) is created in our skin when it is exposed to energy from the sun. In a sense, Vitamin D3 isn’t a true vitamin. With adequate exposure to the sun (UVB) we can get along just fine without supplementation.

There are also forms of Vitamin D in the foods we eat. This form is commonly called Vitamin D2 or “Ergosterol” and can be found in eggs, fish oils, and many plants but generally in low levels. Many food suppliers now add Vitamin D to foods to increase the levels of Vitamin D in our diet.

Now, Vitamins D2 and D3 on their own don’t do much for our bodies – they are raw substances that require some processing before we can put them to use. Through the use of our liver and subsequently the kidneys a series of structural conversions occur creating a compound with the fancy name of 1,24-dihydroxycholecalciferol. Just like its precursors it is what we call a fat soluble compound.

As I am sure you know, we are mostly water and fats don’t dissolve too well in water. To account for this we have special Vitamin D binding proteins which protect the activated Vitamin D and shuttle it throughout our bodies to where we need it most.

Ok, now that our bodies have processed the Vitamin D we need and it is floating around in our bloodstream how do our cells get at it? Well, the Vitamin D carrier proteins pull the Vitamin D through the protective membrane (outer wall) in our cells so that it is exposed to the inner cellular machinery responsible for everyday function. In order for Vitamin D to work though, it needs a way of communicating with our machinery.

Lego_Thumbdrive_by_m_schneiderDeep inside our cells are Vitamin D Receptors. To simplify things, you can think of these receptors as a Lego with two open spots. One clips on to the bioactive Vitamin D, and the other onto our DNA. Once the receptor is clipped onto both, the way our DNA is read changes, and as a result different machines (systems) are turned on or shut down. This leads to a myriad of changes within our bodies. In fact, so many changes occur due to Vitamin D that researchers still don’t know everything that it does!

Ok, to prevent too much information overload I’m going to end here for today. In my next post I will start to go through what researchers think Vitamin D changes in the body. Later this week I will attempt to cover some of the Vitamin D controversy currently being brought up in the news; specifically, can Vitamin D do everything people say it does?

References

Bowen, R. A. (2011) Vitamin D (Calcitriol). Pathophysiology of the Endocrine System. Retrieved June 23, 2013, from http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/vitamind.html

Higdon, J. & Drake V. (2011) Vitamin D. Oregon State University Micronutrient Information Center. Retrieved June 23, 2013, from http://lpi.oregonstate.edu/infocenter/vitamins/vitaminD/index.html

Mayo Clinic (2012) Vitamin D and Related Compounds (Oral Route, Parenteral Route). Mayo Clinic Drug Information. Retrieved June 23, 2013, from http://www.mayoclinic.com/health/drug-information/DR602171

Image: “Medicated Sunshine Remix”  Cryptic Shadows (©2011-2013)

Image: “Lego Thumbdrive” m-schneider (©2009-2013)

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