"Vitamin D is a protein and is likely mostly digested when taken orally. Or not?"
Vitamin D is actually **not a protein**, but a fat-soluble vitamin that plays a key role in calcium metabolism and bone health. There are two main forms of Vitamin D: - **Vitamin D2 (Ergocalciferol)** – plant-based - **Vitamin D3 (Cholecalciferol)** – animal-based or produced in the skin through sun exposure ### How is Vitamin D absorbed in the body? When you take Vitamin D orally (through food or supplements), it is **not digested like proteins**. Since it is fat-soluble, it is absorbed in the small intestine along with fats from food. Here's an overview of the process: 1. **Absorption in the small intestine:** Vitamin D is absorbed in the small intestine with the help of bile acids, which come from food or supplements. The presence of fat in food can improve this process. 2. **Transport into the bloodstream:** After absorption, Vitamin D enters the lymphatic system and then the bloodstream, where it binds to specific transport prote...