What is Vitamin D?

Vitamin D (cholecalciferol) is a fat-soluble vitamin that helps maintain blood levels of calcium by increasing absorption from food and reducing urinary calcium loss. Both functions help keep calcium in the body and therefore spare the calcium that is stored in bones. Though the overall effect of vitamin D on the bones is complicated, it is certainly necessary for healthy bones and teeth.

While Vitamin D is present in some foods, it is also produced by the human body during exposure to the ultraviolet rays of the sun. However, seasonal changes, latitude, time of day, cloud cover, smog and sunscreen can all affect UV exposure. Vitamin D deficiency is more common in northern latitudes, making vitamin D supplementation more important for residents of those areas.

Vitamin D plays a role in immunity and blood cell formation and also helps cells differentiate - a process that may reduce the risk of cancer. From various studies, researchers have hypothesized that vitamin D may protect people from multiple sclerosis, autoimmune arthritis and juvenile diabetes. Vitamin D is also necessary for maintenance of adequate blood levels of insulin. Vitamin D receptors have been found in the pancreas, and some evidence suggests that supplements may increase insulin secretion for some people with adult-onset diabetes