Vitamin K2 and Bone Health

Bones are living tissues that gives support and strength to the body. The living part of our bones is the metabolically active cells in the tissue, while the non-living part is made up of a matrix, a bonding of multiple fibers and chemicals of different materials, including primarily collagen fibers and crystalline salts. The crystalline salts deposited in the matrix of bone are composed principally of calcium and phosphate, which are combined to form hydroxyapatite crystals. The living tissues contains  osteoblasts, a special type of cells building the matrix, and another type of cells, the osteoclasts,  which breaks down and remove matrix  material.  Throughout life there is a balance between these processes; in childhood and in the teens bones are growing and acquiring increased size, mineral content and strength, while after the age of 25 -35 the balance is slowly tipped in favor of loss of matrix and loss of strength. We become more and more brittle as years pass, usually considered a normal physiological process.

For many years vitamin K has been associated to improved bone health due to its unique mechanisms of action: Vitamin K is a co-factor for activation of osteocalcin ‘the calcium binding protein’ secreted by the bone building cells, the osteoblasts.  Osteocalcin is a natural protein which exists in two forms, one inactive form unable to bind calcium and one active form able to bind calcium. The body makes osteocalcin in an inactive form and it needs additional factors to activate the protein. Extensive research has shown that the vitamin K is essential in activating osteocalcin, and thus the binding of calcium to the bone matrix. It is now clear that bone strength is just as important as bone mineral density (BMD) to sustain fractures and preserve good bone health.

While health professionals1 and politicians are debating how to fight osteoporosis and what is important to long term bone health, scientists have for long seen that supplementation of vitamin K is interesting for improving bone health. Science agree to the crucial role of osteocalcin as an important protein for bone health and that inactive osteocalcin2   corresponds to increased risk for osteoporosis and hip fractures3,4,5  . They also agree that vitamin K is an activator of osteocalcin, and that inactive osteocalcin is a useful biomarker for bone health6,7 and vitamin K status8,9,10. However, scientists still discuss the role of vitamin K without differentiating between vitamin K1 and vitamin K2, not to mention the various forms of vitamin K211,12. It is clear from bioavailability studies where vitamin K1 (phylloquinone), menaquinone-4 and menaquinone-7 are compared13,14 that menaquinone-7 is the optimal vitamin K2 for biological effect15,16,17.


References:

1) Annweiler C, Beauchet O. Vitamin D and bone fr