Understanding Vitamin D: Essential Facts for Health

Vitamin D is unique among vitamins because it functions as a hormone, or steroid hormone, produced in the skin when exposed to sunlight. Often called the "sunshine vitamin," it plays a vital role in maintaining overall health. Due to less sun exposure nowadays, it's important to obtain vitamin D through diet or supplements.
Vitamin D is a fat-soluble vitamin, similar to vitamins A, E, and K, meaning it dissolves in fats and oils, allowing it to be stored in the body. There are two primary types:

Vitamin D3 (cholecalciferol), found in fatty fish and egg yolks.

Vitamin D2 (ergocalciferol), present in some mushrooms.

Of these, D3 is nearly twice as effective in raising blood vitamin D levels.
In the body, vitamin D undergoes two conversion steps: first to calcidiol in the liver (storage form), then to calcitriol in the kidneys (active form). Calcitriol interacts with vitamin D receptors across nearly all cells, influencing gene activity and bodily functions. It is crucial for bone health, aiding calcium and phosphorus absorption, but recent research suggests roles in immune regulation and cancer prevention.
Deficiency in vitamin D results in a lack of calcitriol, which can impair vital hormonal functions, affecting multiple bodily systems.