Which vitamin is primarily involved in blood clotting?

Vitamin K plays a crucial role in the process of blood clotting. This vitamin is necessary for the synthesis of certain proteins called clotting factors, which are essential for the blood coagulation process. Without adequate vitamin K, the body would struggle to properly manage bleeding, as clotting factors would not be produced efficiently.

Vitamin K exists in two forms: K1, which is found in green leafy vegetables, and K2, which is produced by bacteria in the human gut. A deficiency in vitamin K can lead to excessive bleeding and bruising because the blood would not clot properly.

In contrast, the other vitamins listed have different roles in the body. For example, vitamin A is important for vision and immune function, vitamin C is crucial for collagen synthesis and antioxidant protection, and vitamin D primarily regulates calcium and phosphorus in the body and is vital for bone health. Thus, vitamin K is distinctly recognized for its direct involvement in blood coagulation, making it the correct answer.