HOW IS VITAMIN D BEING FORMED IN OUR BODY?

Vitamin D formation in our body is a fascinating process — it’s not directly obtained like most vitamins but is actually made by the skin and then activated by the liver and kidneys. Here’s how it works step by step:

🔬 Formation and Activation of Vitamin D

1. Skin Production (First Step)

• In the skin, we have a compound called 7-dehydrocholesterol (a form of cholesterol).
• When exposed to UVB rays from sunlight, this compound is converted into previtamin D3, which then naturally changes into vitamin D3 (cholecalciferol).

2. Transport to the Liver

• Vitamin D3 enters the bloodstream and travels to the liver.
• In the liver, it is converted into 25-hydroxyvitamin D [25(OH)D], also known as calcidiol.
• This is the main circulating form measured in blood tests to check vitamin D levels.

3. Activation in the Kidneys

• From the liver, calcidiol goes to the kidneys.
• The kidneys convert it into the active form, called 1,25-dihydroxyvitamin D [1,25(OH)₂D], also known as calcitriol.
• Calcitriol is the hormone form of vitamin D — it regulates calcium, phosphorus, bone health, immunity, and many other functions.

⚡ Key Points

• Sunlight → Skin → Liver → Kidneys → Active Vitamin D.
• Without proper kidney or liver function, vitamin D activation is impaired.
• That’s why people with chronic kidney disease often need active vitamin D supplements.