Vitamin K2 and bones — does calcium end up in the wrong place without it?

Aim of the study: Vitamin K2 has been approved for the treatment of osteoporosis in Japan since 1995. Vitamin K2 treatment in osteoporosis has been shown to inhibit the occurrence of new bone fractures and to maintain BMD.

Results: Vitamin K2 treatment in osteoporosis has been shown to inhibit the occurrence of new bone fractures and to maintain BMD. The uniqueness of the prevention of bone fractures by vitamin K2 is that there has been no direct evidence of the relationship between increase of BMD and a decrease in the occurrence of bone fractures. A recent systematic review of seven Japanese randomized controlled trials by Cockayne has also shown that supplementation with phytonadione (Vitamin K1) and menaquinone (Vitamin K2) , particularly menaquinone-4, is associated with increased BMD and reduced fracture incidence. To confirm these results, a larger well design RCT using fractures as the primary endpoint is clearly needed.

Aim of the study: In the past decade it has become evident that vitamin K has a significant role to play in human health that is beyond its well-established function in blood clotting. There is a consistent line of evidence in human epidemiologic and intervention studies that clearly demonstrates that vitamin K can improve bone health.

Results: However, there is emerging evidence in human intervention studies that vitamin K(1) at a much lower dose may also benefit bone health, in particular when coadministered with vitamin D. Several mechanisms are suggested by which vitamin K can modulate bone metabolism. Besides the gamma-carboxylation of osteocalcin, a protein believed to be involved in bone mineralization, there is increasing evidence that vitamin K also positively affects calcium balance, a key mineral in bone metabolism. The Institute of Medicine recently has increased the dietary reference intakes of vitamin K to 90 microg/d for females and 120 microg/d for males, which is an increase of approximately 50% from previous recommendations.

Aim of the study: The K vitamins, a group of napthoquinones, are required for the carboxylation of a limited number of proteins including the bone matrix protein osteocalcin. Vitamin K1 (phylloquinone) and vitamin K2 (menaquinones), differ regarding food source (green vegetables and fermented products, respectively), bioavailability and intermediate metabolism.

Results: Epidemiological studies provide evidence for an association between a low vitamin K intake and an enhanced osteoporotic fracture risk. Doses of vitamin K1 up to 15 times the current recommended dietary allowance have successfully been used to reduce the percentage of undercarboxylated osteocalcin in the circulation. Studies demonstrating clear beneficial effects on bone health, however, are still lacking. In contrast, therapy with very high pharmacological doses of the vitamin K2 menatetrenone has impressively been used to prevent further bone mineral loss and fracture risk in osteoporotic patients.

Aim of the study: 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.

Results: 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.

Aim of the study: Osteoporosis (OP) and vascular calcification (VC) represent relevant health problems that frequently coexist in the elderly population. Traditionally, they have been considered independent processes, and mainly age-related.

Results: Vitamin K2 (VitK2), a family of several natural isoforms also known as menaquinones (MK), has recently received particular attention for its role in maintaining calcium homeostasis. In particular, VitK2 deficiency seems to be responsible of the so-called "calcium paradox" phenomenon, characterized by low calcium deposition in the bone and its accumulation in the vessel wall. Since these events may have important clinical consequences, and the role of VitK2 in bone-vascular crosstalk has only partially been explained, this review focuses on its effects on the bone and vascular system by providing a more recent literature update. Overall, the findings reported here propose the VitK2 family as natural bioactive molecules that could be able to play an important role in the prevention of bone loss and vascular calcification, thus encouraging further in-depth studies to achieve its use as a dietary food supplement.

Aim of the study: Inadequate calcium intake can lead to decreased bone mineral density, which can increase the risk of bone fractures. Supplemental calcium promotes bone mineral density and strength and can prevent osteoporosis.

Results: An adequate intake of vitamin K2 has been shown to lower the risk of vascular damage because it activates matrix GLA protein (MGP), which inhibits the deposits of calcium on the walls. Vitamin K, particularly as vitamin K2, is nearly nonexistent in junk food, with little being consumed even in a healthy Western diet. Vitamin K deficiency results in inadequate activation of MGP, which greatly impairs the process of calcium removal and increases the risk of calcification of the blood vessels. An increased intake of vitamin K2 could be a means of lowering calcium-associated health risks.

Aim of the study: Vitamin K (VK) is a fat-soluble vitamin that is indispensable for the activation of vitamin K-dependent proteins (VKDPs). It has been shown to play an important role in the proper calcium deposit at the bone level, hindering that on the vascular walls.

Results: For Vitamin K2 (VK2), there is currently no official reference daily intake (RDI). However, the effects of VK2 on the improvement of health in cardiovascular diseases, on bone metabolism, on chronic kidney diseases have been the subject of research in recent decades. The microbiota in the gastrointestinal tract plays an important role: Bacteroides are primarily capable of synthetizing very long chain forms of menaquinones and, in addition to the bacteria present in the intestinal flora, VK2 is also produced by bacteria used in food fermentation processes. This review provides an update on the current literature regarding the origin of VK2 and its implications in what is called the "calcium paradox", namely the lack of calcium in the bone and its storage in the wall of the vessel.

Aim of the study: Background: The menopausal transition may be accompanied by several disabling symptoms which impair quality of life. Many women cannot proceed with and/or refuse hormonal replacement therapy (HRT) and, thus, they rely on non-hormonal remedies to manage climacteric syndrome.

Results: Comparing Group A and Group B, the values of CTX significantly differed after treatment (p = 0.0458). In comparison to the baseline, significant differences emerged within Group A for physical, psychosocial, and vasomotor domains of Menopause-Specific Quality of Life (MenQol) (p < 0.05) whereas no significant difference was found for the sexual domain (p > 0.05). Comparing Group A and Group B, significant differences were observed for all MenQol domains (p < 0.05), except for the sexual domain (p > 0.05) after therapy. Conclusions: Based on our findings, the combination of PCP, vitD, and vitK2 could be used for managing vasomotor and mood disturbances associated with menopause, whilst also offering the added benefit of maintaining bone health.