Stephan had a great post - Vitamin D: It's Not Just Another Vitamin
If I described a substance with the following properties, what would you guess it was?
-It's synthesized by the body from cholesterol
-It crosses cell membranes freely
-It has its own nuclear receptor
-It causes broad changes in gene transcription
-It acts in nearly every tissue
-It's essential for health
There's no way for you to know, because those statements all apply to activated vitamin D, estrogen, testosterone and a number of other hormones. Vitamin D, as opposed to all other vitamins, is a steroid hormone precursor (technically it's a secosteroid but it's close enough for our purposes). The main difference between vitamin D and other steroid hormones is that it requires a photon of UVB light for its synthesis in the skin. If it didn't require UVB, it would be called a hormone rather than a vitamin. Just like estrogen and testosterone, it's involved in many processes, and it's important to have the right amount.
I was reminded of this by a BBC Story today: Poor health 'due to wet climate'
Scotland's poor health record could be directly linked to a lack of sunshine, a scientist has said. Dr Oliver Gillie linked the "extreme" weather to vitamin D deficiency, which is caused by low exposure to sunlight. He has called for "urgent" government action to encourage people to take a daily dose of vitamin D to help tackle diseases such as cancer and MS.I live in Scotland and - particularly at this time of year - there is little sunlight to be found!
Then I came across this:
What Does Vitamin D Have To Do With Your Back Pain?
There are a number of reasons for why vitamin D deficiency can cause chronic pain.
1. Vitamin D deficiency causes a reduction in calcium absorption.
2. Production of parathyroid hormone is increased to maintain blood calcium levels
3. Parathyroid hormone results in increased urinary excretion of phosphorus, which leads to hypophosphatemia.
4. Insufficient calcium phosphate results in deposition of unmineralized collagen matrix on the endosteum (inside) and periosteum (outside) of bones.
5. When the collagen matrix hydrates and swells, it compresses the sensory-innervated periosteum, resulting in pain.