Vitamin K

Vitamin K is a group of structurally similar fat-soluble vitamins that are required for the complete synthesis of proteins involved in blood coagulation, and for controlling binding of calcium in the bones and other tissues. Without vitamin K, blood coagulation is seriously impaired, and uncontrolled bleeding occurs. Preliminary clinical research indicates that deficiency of vitamin K may weaken bones, potentially leading to osteoporosis, and may promote calcification of arteries and other soft tissues.

Vitamin K includes two natural vitamers: vitamin K1 and vitamin K2:

Vitamin K1

Vitamin K1, also known as phylloquinone, is made by plants, and is found in highest amounts in green leafy vegetables. It performs the classic functions of vitamin K, including its activity in the production of blood coagulation proteins.
Bacteria in the gut flora can convert K1 into vitamin K2.

Vitamin K2

Vitamin K2 or menaquinone, has a similar mechanism of action as vitamin K1. It is suggested that it plays a key role in bone strength and arterial health.
EFSA has acknowledged the following beneficial effects as a basis for health claim:
• Vitamin K contributes to normal blood clotting
• Vitamin K contributes to the maintenance of normal bones