Understanding the Role of Vitamin D in Your Health

Vitamin D is unique among vitamins because it functions more like a hormone, specifically a steroid hormone, produced when the skin absorbs sunlight from cholesterol. Often called the "sunshine" vitamin, it plays a vital role in maintaining overall health. Modern lifestyles limit sun exposure, making it necessary to source vitamin D through diet or supplements.
What exactly is vitamin D?
It is a fat-soluble vitamin, similar to vitamins A, E, and K, meaning it dissolves in fats and can be stored in the body for extended periods. The primary sources include foods rich in omega-3s like fatty fish and egg yolks (Vitamin D3), as well as certain mushrooms (Vitamin D2). Notably, D3 is nearly twice as effective at raising blood vitamin D levels.
Once ingested or synthesized, vitamin D undergoes two conversions: first in the liver to calcidiol (storage form), then in the kidneys to calcitriol, the active hormone. This active form interacts with the vitamin D receptor (VDR) in nearly all body cells, regulating gene expression. It influences bone health by promoting calcium and phosphorus absorption and is additionally linked to immune function and cancer prevention. A deficiency in vitamin D can lead to a lack of calcitriol, impairing these essential processes.