While vitamin D has long been known to assist calcium absorption, it is vitamin K, through its carboxylation of osteocalcin, which guides this calcium to bones and prevents their absorption into organs, joint spaces and arteries. Vitamin K occurs in 3 main forms: K1 (phylloquinone), derived from foods such as green leafy vegetables, K2 (menaquinone) which originates from bacteria; a third form, K3 (menadione), is a synthetic analogue. Numerous studies have shown that vitamin K2 is the more bioavailable form of the nutrient, and more powerfully influences bone building than K1. In addition, though both reach the liver, most of the K1 is used for purposes of coagulation, with little left over to support the body’s needs elsewhere. The profoundly different degrees of bioavailability between K1 and K2 is due to their differences in structure; only 10-20% of vitamin K1 that is absorbed from food even reaches the circulation, while the long side-chain of vitamin K2 allows it to bind with fat particles in circulation and facilitate its arrival at soft tissue, bones and arteries. There are two forms of vitamin K2 commonly used in supplements, synthetic MK-4, and natural MK-7 (extracted from the traditional Japanese food, Natto). The MK-7 form has been shown to have 6 times the activity of MK-4 in the blood. MK-7 has also been found to remain in the blood approximately nine times as long as the MK-4 (8 hours versus 72 hours), making it the optimal form of K2 for health.
A growing body of research shows that when it comes to bone health, ensuring optimal intake of vitamin K is a critical piece of the puzzle. New research is focusing on the synergistic relationship between vitamin K (specifically, vitamin K2) and vitamin D3, especially in terms of bone strength and cardiovascular health. Through its activation of the protein osteocalcin, vitamin K helps to bind newly absorbed calcium to the mineral matrix in bone. In addition, vitamin K has been found to help maintain bone mineral density by decreasing the activity of osteoclasts, a cell that breaks down the bone matrix.Thus, vitamin K and vitamin D not only share similar qualities, but also act synergistically with one another within the body. The Vitamin K2 with D3 formula includes 45 mcg of vitamin K2 delivered as MK-7 and 5,000 IU of vitamin D3 per capsule, for optimal absorption by the body.