Henrik Dam discovered vitamin K, earning the 1943 Nobel Prize in Physiology or Medicine.
Dam identified the vitamin while studying sterol metabolism and blood coagulation in chickens at the University of Copenhagen. Animals fed a fat-free diet developed bleeding problems, suggesting that an unknown fat-soluble substance was required for normal clotting. He called it vitamin K, using the initial from the Danish word “koagulation.”
Vitamin K is essential for producing several proteins involved in blood coagulation. It is found in leafy green vegetables and is also made in small amounts by bacteria in the human intestine. Dam shared the 1943 prize with Edward A. Doisy, who independently isolated and characterized vitamin K. A common mix-up is confusing vitamin K with vitamin C: vitamin C deficiency causes scurvy, whereas vitamin K deficiency primarily impairs clotting.