What deficiency can lead to poor blood clotting?

Vitamin K is essential for the synthesis of certain proteins that are required for blood coagulation, or clotting. When there is a deficiency of this vitamin, the body cannot produce enough of these proteins, which can lead to poor blood clotting. This condition can manifest as easy bruising, excessive bleeding from wounds, or prolonged bleeding after surgery.

Vitamin K plays a crucial role in the body's clotting process by aiding in the production of factors II (prothrombin), VII, IX, and X, which are necessary for managing blood coagulation. Without adequate Vitamin K, the overall ability of the blood to clot effectively is impaired, leading to potentially serious health concerns.

Other vitamins mentioned in the question have different functions in the body; for example, Vitamin A is important for vision and immune function, Vitamin C is vital for the synthesis of collagen and antioxidant protection, and Vitamin E primarily acts as an antioxidant. None of these vitamins have the same direct role in blood clotting as Vitamin K does.