The K used originally denoted koagulation, (from Danish). It was originally discovered by Henrik Dam, who discovered that the addition of putrefying fish powder and alfalfa to the diet of haemorrhaging chickens could staunch the internal bleeding. The compound he isolated was named koagulation vitamin, and the K has been retained by all languages.
The primary purpose of vitamin K is to bring about the normal clotting of blood. It enhances the activity of platelets and participates in many coagulation factors, such as prothrombin. It also seems to help prevent osteoporosis, since K1 catalyzes the metabolism of osteocalcin, the protein matrix of new bones.
There are two natural forms of vitamin K: K1 (phytomenadione), which occurs in leaves of green plants, and K2 (menaquinone), which is formed by intestinal bacteria. A healthy human gut contains these bacteria, and so a person can obtain most of his required vitamin K without eating much. Vitamin K is resistant to heat, water and air, but is sensitive to uv and visible light, so foods containing K vitamins should be kept away from sunlight. Vitamin K is widely available in vegetables such as spinach, cauliflower, peas, soya beans and carrots. It can also be found in liver, egg white and cod liver oil.
Currently, there is no RDA for vitamin K, but it is estimated that 1mg per day is a good amount with which to supplement your diet.
These are rare, but are mostly related to problems in the gut. Patients experience a prolonged clotting time, and are at risk from internal haemorrhaging. The most common sufferers of vitamin K deficiencies are newborn babies, and older children and adults with abdominal diseases that can kill off intestinal flora. Prolonged courses of antibiotics kill off intestinal bacteria. Long term alcoholism, burns treatment and some painkillers (such as acetylsalicylates) have the same effect. Newborn babies are at particular risk from haemorrhaging due to vitamin K deficiency, since the first appearance of intestinal bacteria is after two days. To combat this, doctors often administer vitamin K injections shortly after birth. It is known that very large quantities of vitamin E can inhibit the effect of vitamin K.