The vitamins information pages - Vitamin K
Description Vitamin K
The K in vitamin K is derived from the German word koagulation. Vitamin K is a fat-soluble vitamin which plays a vital role in blood clotting. There are several forms of vitamin K, one synthesized by plants, one synthesized by animals (including humans) and a large range of types synthesized by bacteria in the small intestine of humans. It is stated that the animal variant has some unique function that must still be discovered.
Functions of Vitamin K
Vitamin K delivers the required coenzyme for a vitamin K dependent carboxylation of amino acids. It is essential for the provision of proteins that play a role in blood clotting. Therefore, it is clear that deficiency causes bleeding disorders, such as haemorrhaging (uncontrolled bleeding). This may cause nose bleeds, blood in the urine, or extremely heavy menstrual bleeding. In infants vitamin K deficiency may even result in internal haemorrhaging of the skull. A vitamin K deficiency is fairly uncommon in healthy adults, because bacteria in the intestines synthesize the vitamin. It may however occur in individuals that take medicinal vitamin K antagonists.
Vitamin K in food
Vitamin K is present in cauliflower, soy beans, cottonseed, canola, olives, spinach, Brussels sprouts, broccoli, potatoes, meat, green leafy vegetables and green tea.
Vitamin K as a supplement
Newborns are often vitamin K deficient because they do not have bacteria that produce the vitamin in the gut. This effect is enhanced when the mother takes anti-epileptics.
It is thought that vitamin K also plays a role in bone mineralization, together with vitamin D. This has not been researched to a great extent so far. It leads to the belief that vitamin K may help preventing aging-related osteoporosis. Large doses of supplemental vitamin A and vitamin E have been found to antagonize with vitamin K. Vitamin A prevents absorptions, whereas one form of vitamin E inhibits vitamin K carboxylase enzymes. Medicines such as isoniazid, warfarin and anticonvulsants can interfere with foetal vitamin K synthesis in pregnant women. This may cause infant vitamin K deficiency. Vitamin E absorption may be decreased by a number of medicines, such as cholestyramine, mineral oil, sucralfate, and the fat substitute olestra. Long-term use of broad-spectrum antibiotics may affect bacteria responsible for vitamin K synthesis in the intestines.
People that use anti-clotting medication should not take vitamin K. Liver disease results in decreased blood vitamin K levels, which may cause decreased blood clotting resulting in uncontrolled bleeding. Patients that take medication against blood clotting (vitamin K antagonists) must make sure their diets do not contain too much vitamin K. It is advised that vitamin K intake does not exceed 120 µg.
Descriptions of vitamins on this website are based on information provided by BBC Health and The Linus Pauling Institute.