What is Vitamin D

Vitamin D is a vitamin that helps keep your bones strong, supports your immune system, and can even help with your energy and mood. There are two main types: Vitamin D2, which comes from plants like mushrooms and fortified foods, and Vitamin D3, which is found in animal foods like fish and eggs and is also made by your skin when you’re in the sun. Your body changes these into forms it can use—first into a storage form called calcidiol, made in the liver, and then into the active form called calcitriol, made in the kidneys. Calcitriol helps your body use calcium and phosphorus to build healthy bones and teeth.

Your body stores and manages vitamin D in a few places. It starts in the skin when you get sunlight, then moves to the liver where it gets stored as calcidiol. It can also be stored in your body fat for long-term use. When your body needs active vitamin D, your kidneys step in and make calcitriol from the stored version. The bloodstream helps carry all these forms around to where they’re needed. Special systems in your body, like certain hormones, help control how much is made and used. Having enough vitamin D stored in your body is important, especially during times when you don’t get much sunlight. Without enough, you could become deficient, which can lead to weak bones or other health problems.