25-hydroxy calcifediol, also known as cholecalciferol, at first glance seems to be related to vitamin D3, they’re very similar, in fact, adding a hydroxyl group to the 25th carbon atom of vitamin D3, through a series of biochemical reactions in the body, 25-hydroxy calcifediol is obtained by hydroxylation of 25-hydroxylase in mitochondria of liver cells. So, what’s the difference between 25-hydroxy calcifediol and vitamin D3?
Vitamin D3 is a precursor of active metabolites and is not biologically active, whereas 25-hydroxy calcifediol is a biologically active substance. The two are stored in different places in the body, 25-hydroxy calcifediol is stored in the liver and vitamin D3 is stored in the liver, fat, plasma, and muscle. The body absorbs the two differently; 25-hydroxy calcifediol is easier to absorb than vitamin D3 and can be absorbed directly from the gut into the bloodstream. In terms of absorption rate, 25-hydroxy calcifediol has a higher absorption rate than vitamin D3 and can be converted more quickly and efficiently, bypassing the liver, while 25-hydroxy calcifediol has a shorter metabolic process and helps promote calcium absorption in the body.