Vitamin K activates prothrombin and the other blood clotting factors, and is a necessary nutrient to make the blood clotting activity work properly. Recently, it has been also found that Vitamin K is needed in order that the protein osteocalcin existing in human bones may function properly. A distinctive amino acid, γ- carboxyglutamin acid (Gla), is in the proteins depending on Vitamin K. It can't be made without Vitamin K.

In the type of the proteins like the osteocalcin the glutamic acid is transformed into Gla by Vitamin K, and it enhances the affinity to calcium. These proteins are combined with calcium Ion, and the strength of the combination with hydroxyapatites gets stronger. It has been reported that in middle aged people the ratio of osteocalcin with the inadequate transformation into Gla gets higher, and administering Vitamin K to them, the transformation into Gla will be accelerated.

Vitamin K helps to maintain the normal blood clotting activity and plays an important role in the prevention of osteoporosis by the improvement of the bone formation.
Natural Vitamin K is classified roughly into Vitamin K1 (Phylloquinone ) and Vitamin K2 (Menaquione),and both are almost the same in the biological activities.
Vitamin K1 is synthesized by the vegetal chloroplast and is included much in green leaves vegetables such as spinach, etc and the sea alga - especially, the outside leaves of vegetables catching the sun. Vitamin K2 is included in milk, dairy products, meats, eggs, and the general vegetables and is also made by the intestinal bacteria.

It is clear that the deficiency disease is related to only blood clotting. It is known that the cause of the gut hemorrhage and the intracranial hemorrhage in newborn babies is from the deficiency of Vitamin K. In the clinical area it is being recommened to administer Vitamin K to newborn babies. That's why pregnant women should take foods including adequate Vitamin K. It is reported that the concentration of Vitamin K in blood rises by the intake of Chlorella. It means that Chlorella is very helpful in order to supplement Vitamin K.