Vitamin D For Good Health

Vitamin D is a fat-soluble steroid hormone that regulates calcium homeostasis and is vital for bone health. It exists in two molecular forms. In animal skin it exists as vitamin D-3 (cholecalciferol), and in plants, mushrooms, and yeast it exist as vitamin D-2 (ergocalciferol). These two forms are created by the action of the sun’s ultraviolet rays on the biological precursors, 7-dehydrocholesterol, and ergosterol. Chole-calciferol and ergocalciferol are biologically inactive precursors of vitamin D and must be converted to biologically active forms in the liver and kidneys.

For most humans, exposure to sunlight is the major source of vitamin D. When exposed to sunlight, the ultraviolet-B radiation enters the skin where 7-dehydrocholesterol is converted to pre-vitamin D3. Within the plasma membrane pre-vitamin D3 rapidly converts to Vitamin D3 which is then mobilized into the extracellular space where it is bound to vitamin D receptors.

Following dietary intake or its production in the epidermis when ultraviolet rays from sunlight strike the skin, both forms enter the circulation and are transported to the liver by the vitamin D-binding protein (and to a lesser extent by albumin). Vitamin D must undergo two hydroxylations in the body for activation. These two hydroxylations and their effect on our nervous and immune system are explained in the book, "Caring Your Bones Today for the Future".

There are many functions of the active form of vitamin D, including the vital role in maintaining an efficient immune system. Under certain circumstances, monocytes, macrophages, and T-cells can express the 25-hydroxyvitamin D3-α-hydroxylase enzyme and produce 1,25-dihydroxyvitamin D, which acts locally to regulate the immune response. It is also involved in the inhabitation of the proliferation of cancer cells and stimulates the differentiation of cells through binding to the vitamin D receptors.

 

In addition to bone loss, research concluded that vitamin D deficiency is associated with heart disease, some cancers, multiple sclerosis, and infectious diseases such as tuberculosis and flue.

Sunlight exposure can provide most people with their entire vitamin D requirement. There are however, many different factors that affect the rate at which this vitamin is produced from sunlight exposure. The book Caring Your Bones Today for the Future gives detailed information about these factors and how they affect the rate at which you produce this vitamin from sunlight.

 

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