Abstract Objective. To review the evidence for the use of vitamin K supplementation in clinical conditions such as osteoporosis, vascular calcification, arthritis, cancer, renal calculi, diabetes, and warfarin therapy. Quality of Evidence. PubMed was searched for articles on vitamin K (K1 and K2) along with books and conference proceedings and health conditions listed above. Level I and II evidence supports the use of vitamins K1 and K2 in osteoporosis and Level II evidence supports vitamin K2 in prevention of coronary calcification and cardiovascular disease. Evidence is insufficient for use in diabetes, arthritis, renal calculi, and cancer. Main Message. Vitamin K2 may be a useful adjunct for the treatment of osteoporosis, along with vitamin D and calcium, rivaling bisphosphonate therapy without toxicity. It may also significantly reduce morbidity and mortality in cardiovascular health by reducing vascular calcification. Vitamin K2 appears promising in the areas of diabetes, cancer, and osteoarthritis. Vitamin K use in warfarin therapy is safe and may improve INR control, although a dosage adjustment is required. Conclusion. Vitamin K supplementation may be useful for a number of chronic conditions that are afflicting North Americans as the population ages. Supplementation may be required for bone and cardiovascular health. Full article
Vitamin K2 MK-7 regulates the extrahepatic movement and uptake of calcium in the body; or, more simply, K2 regulates the distribution of calcium. MK-7 activates the proteins that incorporate calcium into bones (where it is needed) and activates the proteins that bind calcium to prevent deposits in arteries and smooth muscle walls (where it increases cardiovascular risk factors).
Vitamin K2 is an essential cofactor for the activation of proteins belonging to the Gla-protein family, of which one of the most studied is osteocalcin. Osteocalcin plays a role in the integration of calcium into the bone matrix, a function that defines vitamin K2 as essential to bone health. Vitamin K2 MK-7 is also essential for the activation of matrix Gla-protein (MGP).6 After MGP is activated (in a carboxylation process initiated by vitamin K2), MGP binds free-floating calcium to prevent it from being deposited in vascular smooth muscle cells.7 Without MGP activation, unbound calcium is free for deposit in arteries and vascular smooth muscle walls. In plain language, K2 prevents calcium from being deposited in arteries, making it essential for heart health.
MK-7 vs MK-4
Abstract Background Vitamin K2 contributes to bone and cardiovascular health. Therefore, two vitamin K2 homologues, menaquinone-4 (MK-4) and menaquinone-7 (MK-7), have been used as nutrients by the food industry and as nutritional supplements to support bone and cardiovascular health. However, little is known about the bioavailability of nutritional MK-4. To investigate MK-4 and MK-7 bioavailability, nutritional doses were administered to healthy Japanese women.
Findings Single dose administration of MK-4 (420 μg; 945 nmol) or MK-7 (420 μg; 647 nmol) was given in the morning together with standardized breakfast. MK-7 was well absorbed and reached maximal serum level at 6 h after intake and was detected up to 48 h after intake. MK-4 was not detectable in the serum of all subjects at any time point. Consecutive administration of MK-4 (60 μg; 135 nmol) or MK-7 (60 μg; 92 nmol) for 7 days demonstrated that MK-4 supplementation did not increase serum MK-4 levels. However, consecutive administration of MK-7 increased serum MK-7 levels significantly in all subjects.
Conclusions We conclude that MK-4 present in food does not contribute to the vitamin K status as measured by serum vitamin K levels. MK-7, however significantly increases serum MK-7 levels and therefore may be of particular importance for extrahepatic tissues. KeywordsVitamin K2Menaquinone-4Menaquinone-7BioavailabilityAbsorption
While K1 is preferentially used by the liver to activate blood clotting proteins, K2 is preferentially used by other tissues to deposit calcium in appropriate locations, such as in the bones and teeth, and prevent it from depositing in locations where it does not belong, such as the soft tissues.(Spronk et al., 2003, pp. 531-537) In an acknowledgment of the different roles played by vitamins K1 and K2, the United States Department of Agriculture (USDA) finally determined the vitamin K2 contents of foods in the U.S. diet for the first time in 2006. (Elder, Haytowitz, Howe, Peterson, & Booth, 2006, pp. 436-467) Another common misconception is that human beings do not need vitamin K2 in their diet, since they have the capacity to convert vitamin K1 to vitamin K2. The amount of vitamin K1 in typical diets is ten times greater than that of vitamin K2, and researchers and physicians have largely dismissed the contribution of K2 to nutritional status as insignificant.
Vitamin K deficiency increases the risk of excessive bleeding (hemorrhage). An injection of vitamin K is recommended to protect all newborns from life-threatening bleeding within the skull. (More information)
The adequate intake (AI) level for vitamin K is set at 90 μg/day for women and 120 μg/day for men. (More information)
Vitamin K deficiency may impair the activity of VKDPs and increase the risk of osteoporosis and fractures. Yet, observational studies have failed to isolate vitamin K intakes from overall healthful diets, thus warranting cautious interpretation of positive associations between vitamin K intakes and markers of bone health. Overall, intervention trials have been inconclusive regarding the role of supplemental vitamin K in further reducing bone loss in otherwise calcium- and vitamin D-replete adults. (More information)