Vitamin D – Uses, Benefits, Sources and Dosage Vitamin D is also among the nutrients which our body needs in order to stay healthy. Functions of Vitamin D Here are some important functions of this vitamin: The vitamin helps the body to absorb calcium. This vitamin along with calcium helps to maintain the strong bones. There is a hormone, called parathyroid hormone, which reabsorbs the bone tissue as well as makes them thin and brittle. Vitamin D blocks this hormone