The aim of the present review is to discuss the roles of vitamin K (phylloquinone or menaquinones) and vitamin K-dependent proteins, and the combined action of the vitamins K and D, for the maintenance of bone health. The most relevant vitamin K-dependent proteins in this respect are osteocalcin and matrix Gla-protein (MGP). When carboxylated, these proteins appear to have the ability to chelate and import calcium from the blood to the bone, thereby reducing the risk of osteoporosis. Carboxylated osteocalcin appears to contribute directly to bone quality and strength. An adequate vitamin K status is required for the carboxylation of MGP and osteocalcin. In addition, vitamin K acts on bone metabolism by other mechanisms, such as menaquinone 4 acting as a ligand for the nuclear steroid and xenobiotic receptor (SXR). In this narrative review, we examine the evidence for increased bone mineralization through the dietary adequacy of vitamin K. Summarizing the evidence for a synergistic effect of vitamin K and vitamin D3, we find that an adequate supply of vitamin K, on top of an optimal vitamin D status, seems to add to the benefit of maintaining bone health. More research related to synergism and the possible mechanisms of vitamins D3 and K interaction in bone health is needed.

The aim of the present review is to discuss the roles of vitamin K and vitamin K-dependent proteins, and the combined action of the vitamins K and D, for maintenance of bone health. The most relevant vitamin K-dependent proteins in this respect are osteocalcin and matrix Gla-protein (MGP). When carboxylated these proteins appear to have the ability to chelate and import calcium from the blood to the bone, thereby reducing the risk of osteoporosis. Carboxylated osteocalcin appears to contribute directly to bone quality and strength. Adequate vitamin K status is required for carboxylation of MGP and osteocalcin. In addition, vitamin K acts on bone metabolism by other mechanism, such as a ligand for the nuclear steroid and xenobiotic receptor (SXR). In this narrative review, we examine the evidence for increased bone mineralization through dietary adequacy of vitamin K (phylloquinone or menaquinone). Summarizing the evidence for a synergistic effect of vitamin K and vitamin D3 we find that an adequate supply of vitamin K on top of an optimal vitamin D status seems to add to the benefit for maintaining bone health. More research related to synergism and possible mechanisms of vitamins D3 and K interaction in bone health is needed.

Objective: The aim of this study was to determine the biological effects of natural dietary intake of vitamin K as phylloquinone (K₁) and menaquinone-4 (MK-4) and a control diet also containing menadione (K₃) on levels of K₁ and total MK-4 (menaquinone-4) and menaquinone-4-2,3-epoxide (MK-4O) in liver and pancreas, and on femur bending resistance in a fast-growing animal model. Design: Chickens were fed four wheat-based diets from day 11 to day 22 after hatching. The diets contained different combinations of fat sources: rapeseed oil, animal rendered fat, soybean oil and hydrogenated soybean oil. Concentration of K₁ in the three experimental diets was 120 ng/g whereas MK-4 levels were 23, 52 and 63 ng/g respectively. The control diet contained 157 ng K₁/g, 75 ng MK-4/g and 2.250 ng K₃/g. Results: Growth rates and femur strength confirmed adequate supply of nutrients and vitamin K in the test groups. There were no significant differences in femur bending resistance among the test groups, but these were higher than the control. K₁, MK-4 and MK-4O were found in liver. In pancreas, mainly MK-4O was found with small amounts of MK-4, but none had content of K1. In the test groups the hepatic levels of MK-4 and MK-4O reflected the dietary intake of MK-4. Conclusion: The chickens were in good health with good bone resistance without supplements of K₃in the feed, but at least a natural content of 23 ng MK-4/g feed. Liver and pancreas appears to use MK-4 in different ways.Keywords: Menaquinone-4; diet; liver; pancreas; chicken (Published: 2 April 2012) Citation: Food & Nutrition Research 2012. 56: 5380 - DOI: 10.3402/fnr.v56i0.5380