Vitamin D3 Called the sunshine vitamin, vitamin D isformed naturally in the skin by exposure to sunlight. Butwhen an individual does not get enough sun exposure,their body cannot make sufficient vitamin D. Vitamin Dsupplementation is especially important because it’s hardto get enough during our long, dark northern winters.Vitamin D is a vitamin and hormone that stimulates thebody to absorb calcium, and it is needed to keep bonesstrong. People deficient in vitamin D levels tend to havesofter, thin bones, predisposing them to fractures. VitaminD is especially important for the elderly because of theirdifficulty synthesizing vitamin D from sunlight as somemedications interfere with vitamin D absorption.