- Vitamin K
Vitamin K was discovered through a series of experiments in the early 1930s conducted by Henrik Dam who was investigating the possible essential role of cholesterol in the diet of the chick. Dam  noted that chicks ingesting diets that had been extracted with nonpolar solvents to remove the sterols developed hemorrhages and that blood taken from these animals clotted slowly. Subsequently, McFarlane et al.  and Holst and Halbrook  described clotting defects seen when chicks were fed ether-extracted sh or meat meal, or internal and external hemorrhages in chicks fed sh meal and yeast as a protein source. This disease could not be cured by the administration of any of the known vitamins. Dam continued to study the active component in vegetable and animal sources and in 1935 proposed [4,5] that the antihemorrhagic vitamin of the chick was a new fat-soluble vitamin, which he called vitamin K. Not only was K the rst letter of the alphabet that was not used to describe an existing or postulated vitamin activity at that time, but it was also the rst letter of the German word koagulation.