Who discovered the blood-clotting factor later known as vitamin K?

Henrik Dam discovered the blood-clotting factor later known as vitamin K.

In the late 1920s and early 1930s, Danish biochemist Henrik Dam studied chickens fed a fat-free diet. The animals developed bleeding problems, and Dam concluded that they lacked an essential dietary factor needed for normal coagulation. He called it Koagulationsvitamin, using the German-derived letter K.

American chemist Edward Doisy independently isolated and characterized vitamin K compounds. Dam received the 1943 Nobel Prize in Physiology or Medicine for discovering vitamin K, while Doisy shared the prize for his work on its chemical nature.

Vitamin K is required to activate several clotting proteins made by the liver. Newborn babies are commonly given vitamin K because they have low stores and can otherwise develop serious bleeding. Vitamin K is not the same as a clot-forming drug; it is a nutrient essential to the body's coagulation system.