Which vitamin is essential for blood clotting processes?

• A. Vitamin A
• B. Vitamin D
• C. Vitamin C
• D. Vitamin K

Answer: (D)

Vitamin K is essential for blood clotting because it enables the gamma-carboxylation of several key clotting factors (II, VII, IX, and X) as well as proteins C and S. This chemical modification allows these proteins to bind calcium and interact properly on platelets and phospholipid surfaces, which is necessary for forming a stable clot. Without this activation step, the coagulation cascade cannot proceed effectively, leading to impaired clotting and a higher risk of bleeding.

Vitamin A, D, and C have important roles in vision and epithelial health, bone and calcium metabolism, and collagen synthesis/antioxidant protection, respectively, but they do not drive the clotting process.