Differences In The Activation Of Vitamin D Types
The activation process involves the conversion of vitamin D from cutaneous synthesis and diet in either the D2 or D3 form which is biologically inactive until it goes through two enzymatic hydroxylation chemical reactions in the body. The first reaction occurs in the liver along with the mediation by the 25-hydroxylase that turns in hydroxy-vitamin D. the second reaction occurs in the kidney following by the mediation of 1 α-hydroxylase, which then ultimately converts 25OHD into a biologically active calcitriol pheromone. The 1α-hydroxylase gene expresses itself in various extra-renal tissues as its participation to calcitriol formation is unknown. 25OHD is the precursor of calcitriol, which is the main circulation form of vitamin D. calcitriol’s circulation remains to a specific plasma carrier protein which is known as vitamin D binding protein (DBP). Vitamin D binding protein (DBP) also moves vitamin D and calcitriol. Moreover, most of the food labels indicate vitamin D2 as vitamin D. while vitamin D3 appears as it is on nutrition labels.
Vitamin D is not a single substance but rather a group of related nutrients. The most common dietary forms include vitamin D2 and D3. The vitamins D2 and D3 differs only in terms of their side chain structure but the difference does not affect the metabolism or activation. Therefore, both the types of vitamin D act as prohormones. Upon activation, the D2 and D3 show identical responses in the body and the potency of both these forms to treat vitamin D deficiency rickets is also the same. Some experimental studies on animals indicate that vitamin D2 is less toxic rather than vitamin D3, but there are no clear demonstrations in humans about that.