Adequate vitamin D intake is essential for optimal health. The body depends on it for a variety of health and wellness processes, from a robust immune system to strong bones and improved mental health. It also lowers the risk of some cancers. Vitamin D may help the body fight off pathogens that cause colds, the flu and other diseases as well as alleviate some of the inflammation brought on by autoimmune illnesses.

It can be challenging to get enough vitamin D, though, due to the nature of the nutrient. About one in four Americans is thought to be vitamin D deficient. When deficient, a vitamin D injection can be helpful, as vitamin D3 is absorbed most effectively when it enters the circulation right away.