In 1929 Dam a Danish scientist, observed that chicks fed on a synthetic diet developed hemorrhages and diet. This was due to prolonged blood clotting time. Dam noticed that this could be prevented by the addition of alfalfa grass to the diet. The curative factor contained in this grass was isolated and was found to be present also in leafy vegetables, especially spinach. It was called vitamin K because of its role in the coagulation in the blood (spelt koagulation in European languages).
Vitamin K is found in nature in two forms: k1 occurs in green leaves and K2 is produced by bacterial synthesis. These are soluble in fats. They are not destroyed by heat, but are unstable to alkalies, strong acids, oxidation and light.
Vitamin K is often called “coagulation vitamin” because it has anti– hemorrhagic properties. This is essential for the synthesis of prothrombin, the precursor of thrombin, one of the factors needed for the normal coagulatory function of blood. A blood clot is made up of fibrin, a protein, which is deposited as fine threads to form a net-work. The formation of fibrin from prothrombin requires calcium and Vitamin K may be an essential part of the enzyme system involved in the production of the blood clotting factor.
Prothrombin + calcium + vitamin K=thrombin
Thrombin + fibrinogen = fibrin (Blood Clot)
Vitamin K mainly occurs in plants. Green leaves of plants such as spinach and also cabbage, cauliflower, Soya bean and vegetable oils are good sources of vitamin K. Cereals, fruits and other vegetables are poor sources. Animal products contain much less vitamin K, but pork liver is a good source. Since this vitamin is present in a large variety of commonly eaten plant foods and it can be synthesised in the intestinal tract by bacteria and because of its stability and insolubility in water, the person does not usually suffer from vitamin k deficiency.
It is not possible to recommend a daily allowance of vitamin k because of the variation in the intestinal synthesis of the vitamin and in the diet. Dietary deficiency is not believed to be a problem.
Deficiency results usually from a faulty absorption of the vitamins or due to liver disorders that effect the synthesis of the prothrombin. Dietary lack of vitamin K is rather unusual and adequate supply of its normally available in the body for reason mentioned earlier. The intake of large amount of sulfa drugs or other antibiotics can, however destroy microorganisms which synthesise the vitamin, resulting in deficiency. Premature infant and those whose mother have been taking anticoagulants are also susceptible to a deficiency. New-born infants may have vitamin K deficiency because micro-organisms of the right type may not have had time to get established in the intestinal tract. The deficiency of vitamin K results in low blood levels of prothrombin and other clotting factors leading to an increased tendency haemorrhage.
Since vitamin K is fat soluble the presence of bile is necessary for its absorption. Disorders of the liver or gall bladder which interfere with the secretion of bile could result in vitamin K deficiency.