Which vitamin helps with blood clotting?

Vitamin K plays a crucial role in the blood clotting process, which is essential for stopping bleeding when injuries occur. It is involved in the synthesis of certain proteins that are prerequisites for blood coagulation, specifically prothrombin, which is a key protein in the coagulation cascade. Without adequate vitamin K, the body cannot produce sufficient amounts of these clotting factors, leading to a higher risk of excessive bleeding.

While other vitamins listed have important functions in the body, they do not directly influence the coagulation process. For instance, vitamin D is primarily involved in calcium metabolism and bone health, vitamin A is essential for vision and immune function, and vitamin B12 is crucial for red blood cell formation and neurological function. None of these vitamins contribute to the specific mechanism of blood clotting that vitamin K does. Thus, vitamin K's unique role in facilitating proper clotting makes it the correct answer.