Vitamin D is a vitamin that is essential for human health. It is involved in calcium absorption, bone and muscle health, and immune function. Vitamin D can be obtained from food or supplements, but the body can also synthesize vitamin D when exposed to sunlight.
Vitamin D deficiency can lead to a number of health problems, including osteoporosis, rickets, and impaired immune function. Vitamin D supplementation is often recommended for people who are at risk for vitamin D deficiency. Take a look at my article - the 10th reason why you are vitamin D deficient to get a better understanding.
There is some evidence that vitamin D may have other benefits as well, such as reducing the risk of certain cancers and promoting cardiovascular health.