Vitamin K occurs in at least two major forms- Vitamin K1 & Vitamin K2. Vitamin K1 is found mainly in fresh green vegetables particularly dark green ones & in some fruits. Cow’s milk is a richer source of vitamin K than human milk.
Vitamin K2 is synthesized by the intestinal bacteria, which usually provide an adequate supply in man. Long-term administration doses for more than a week may temporarily suppress the normal intestinal flora & may cause a deficiency of vitamin K. Vitamin K is stored in the liver.
The role of vitamin K is to stimulate the production or release of certain coagulation factors. In vitamin K deficiency, the prothrombin content of blood is markedly decreased & the blood clotting time is considerably prolonged.The vitamin K requirement of man is met by a combination of dietary intake & microbial synthesis in the gut.
The daily requirement for man appears to be about 0.003 mg/kg for the adult. Newborn infants tend to be deficient in vitamin K due to minimal stores of prothrombin at birth & lack of an established intestinal flora. Soon after birth, all infants or those at increase risk should receive a single intramuscular dose of a vitamin K preparation by way of prophylaxis.