Vitamin K: The Missing Link to Bone Health?

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Researchers from the Keio University School of Medicine have recently reported that vitamin K supplementation plays an important role in preventing fractures.

Vitamin K exists in several forms including vitamin K1 (phytonadione) and vitamin K2 (menaquinone). This study is a meta-analysis of seven studies with postmenopausal women to evaluate their fracture risk and its association with their intake of vitamin K. Each of the studies reviewed had at least 50 subjects and lasted a minimum of 2 years.

The data from the meta-analysis showed that both forms of vitamin K supplementation reduced serum under-carboxylated osteocalcin levels. The normal remineralization of bone requires osteocalcin. Vitamin K is the cofactor that activates osteocalcin. Think of this as the bone forming phase. If the body is under-carboxylated osteocalcin meaning it is less active, which is caused by insufficient vitamin K levels. This results in decreased calcium binding and bone mineralization. The researchers also found that vitamin K consumption had inconsistent effects on total serum osteocalcin levels and had no effect on bone re-absorption or the breaking down phase. However, the study revealed that high-doses of either form of vitamin K supplementation improved bone strength indices in the hip and reduced the incidence of clinical fractures overall.

The researchers stated, “The review of the reliable literature confirmed the effect of vitamin K1 and vitamin K2 supplementation on the skeleton of postmenopausal women mediated by mechanisms other than bone mineral density and bone turnover.”

Vitamin K1 is the major dietary form of vitamin K. Green leafy vegetables and some vegetable oils (soybean, cottonseed, canola, and olive) are major contributors of dietary vitamin K. Hydrogenation of vegetable oils may decrease the absorption and biological effect of dietary vitamin K. Vitamin K2 is synthesized from intestinal bacteria but the amount that makes it into the blood stream is unclear. The minimum recommended daily amount is 90 mcg for women and 120 mcg for men. Daily supplementation ranges from 10 mcg to 1000 mcg in the various clinical studies. The Framingham Heart Study recommends supplementing at least 250 mcg per day to decrease the risk of hip fractures.

These studies gives another reason why you need to listen to your mother and eat your vegetables…especially the dark green leafy ones!