Biological importance of C-3 alpha epimer of 25-hydroxy vitamin D regarding bone mineral density in young and adult rats

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Vitamin D is a nutrient that helps bones grow and stay strong. In Canada, the main dietary source of vitamin D comes from milk. Milk has vitamin D added in amounts that help to prevent the body from having very low stores of this vitamin D. Recently, a new form of vitamin D, called C-3 epimer, has been discovered in blood samples taken from infants and adults. The only difference is that one chemical bond has a different orientation, however, this might alter how well it works. For example, vitamin D works by binding to receptors in the body's cells in a similar way as using a key in a lock to open a door. A small change could alter how the key works. Therefore, it is unclear if the C-3 epimer is as good as the normal form of vitamin D in helping bones grow and stay strong. This research is designed to test if higher intakes of vitamin D result in proportional increases in C-3 epimer and to test if this has any consequences to growing or adult bone. The work will be conducted in young and mature rats over 8 weeks of feeding various amounts of the vitamin D forms. Bone will be examined by taking a series of x-rays specially designed to show how much calcium is packed into bone and also to estimate bone strength. The results will help the dairy industry to know where the C-3 epimer comes from and if it is good for bone.