This document discusses vitamin D, including what it is, why it is important, factors that can lead to vitamin D deficiency, symptoms of deficiency, and supplementation recommendations. Vitamin D enhances nutrient absorption and is important for bone and overall health. It can be obtained from sunlight or dietary sources. Many people have inadequate vitamin D levels due to less sun exposure and other lifestyle factors. Symptoms of deficiency are nonspecific but supplementation can help address deficiency.