Which vitamin is needed for bone development and is often added to milk?

Vitamin D plays a crucial role in bone development and health. It facilitates the absorption of calcium and phosphorus from the diet, which are essential minerals for the formation and maintenance of strong bones. Without adequate levels of vitamin D, bones can become weak and brittle, leading to conditions such as rickets in children and osteomalacia in adults.

Milk is often fortified with vitamin D to help prevent deficiencies in the population, as many individuals may not get enough sunlight exposure, which is a natural source of vitamin D. This fortification is particularly important in regions with limited sunlight, especially during the winter months.

In contrast, while vitamins C, A, and K have important functions in the body, they are not primarily associated with bone development in the same way that vitamin D is. Vitamin C is essential for collagen formation and supports the immune system, vitamin A is important for vision and immune function, and vitamin K is critical for blood clotting and also plays a role in bone metabolism, but it does not directly enhance calcium absorption like vitamin D does.