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Requirements
Much of the body's supply of vitamin K is synthesised by bacteria in the digestive tract. Food sources of vitamin K are liver, green leafy vegetables, cabbage-type vegetables and milk.

Best sources
The digestive tract of humans contains bacteria that synthesise vitamin K, which is partly absorbed and stored in the liver. The body needs to take in additional vitamin K in the diet.

Functions
Vitamin K is essential for the synthesis for some of the proteins involved in blood clotting. Vitamin K is also needed for bone formation.

Deficiency symptoms
If vitamin K is missing, blood cannot clot. This can lead to haemorrhagic disease. However, vitamin K deficiency is rare.; only babies are susceptible to it. This is because the digestive tracts of new-born babies are sterile and do not contain the bacteria that synthesise vitamin K Also, breast milk contains only small amounts of vitamin K. This is why babies are given a dose of vitamin K at birth.

Toxicity
Vitamin K toxicity occurs only in people who take water-soluble substitutes for vitamin K. Symptoms are red cell hemolysis, jaundice and brain damage.