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Having strong healthy bones is important throughout all stages of life. Insufficient dietary intake of vitamins and minerals may impact on bone quality. Adequate calcium is essential through life and is crucial for strong healthy bones. Inadequate calcium leads to osteopenia or osteoporosis.1 More than 66% of Australians over the age of 50 have poor bone health.2
Just as insufficient dietary calcium may lead to weak, brittle bones, excess calcium in the body may contribute to cardiovascular conditions.
Some questions have been raised over a possible connection between calcium supplementation and increased cardiovascular risk due to vascular calcification.6 The body contains many proteins including osteocalcin and matrix Gla-protein (gamma carboxyglutamate), which regulate calcium balance.78 Both calcification activity and MGP (matrix Gla Protein) activity are correlated with vitamin K2 intake.9
Vitamin K is a fat-soluble vitamin that the body stores in the liver and fat cells. It is available in three forms:10
All three forms are metabolically activated in the liver to become co-factors in the activation of vitamin K-dependent proteins that are important for normal blood coagulation, and normality of bones and arteries (Gla-proteins).12 The only structural difference between vitamin K1 and K2 is the side chain. Vitamin K2 has side chain of repeating isoprenoid units (phytyl side-chain). The common bioactive region (menadione comprising a methylated naphthoquinone ring) of both K1 and K2 molecules is identical. It is understood that vitamin K2 is more resistant to hepatic metabolism allowing vitamin K2 to travel systemically in the body to other tissues.1314
Vitamin K was first identified as an essential vitamin required for blood clotting through acting as a cofactor in the normal biosynthesis of several plasma blood clotting factors (factors II, VII, IX and X).15 Vitamin K1 appears to have a short half-life of one-two hours,15 needing to be replaced through the diet regularly.15
Vitamin K supports the body’s calcium balance for strong bones and is thought to play an integral role in calcium
absorption into the bone.161718 Vitamin K2 optimises the calcium balance by activating osteocalcin and matrix Glaprotein.171819 When vitamin K status is inadequate, these two proteins are not carboxylated as they would normally be, and therefore, have limited ability to bind to calcium and aid in bone mineralisation.19
People at risk for developing vitamin K deficiency include those with chronic malnutrition (including those with alcohol dependency) or conditions that limit absorption of dietary vitamins, such as various gut issues.20
Vitamin K2 (MK-7) is well-absorbed and has a longer half-life than vitamin K1, remaining in the body for approximately
72 hours.12 Both calcification activity and MGP (matrix Gla Protein) activity are correlated with vitamin K2 intake8,
however larger interventions with longer follow-up will further clarify the role of vitamin K2 in optimising calcium balance.
In young healthy people (20 to 40 years old) and older people (60 to 80 years old) an increase in daily intake of vitamin K for 5 days from 100 to 420 μg, reduced the undercarboxylated fraction of ostecalcin by 40%.21
Studies of postmenopausal women who have taken vitamin K2, show beneficial effects on bone health. One placebocontrolled study examined the effect of fortified dairy products on parameters of bone metabolism in postmenopausal women following a 12-month intervention. Each intervention group provided 800mg calcium, and 10μg of vitamin D while two were also enriched with 100μg of either phylloquinone (CaDK1) or menaquinone-7 (CaDK2). This study showed more favourable changes on bone metabolism and bone mass indices for the CaDK2 (as well as CaDK1) supplemented group compared to the group receiving calcium and vitamin D only.22
Another placebo-controlled study conducted over a three year period resulted in a decrease in age-related decline in bone mineral content and density at the lumbar spine and femoral neck with MK-7 intake. Bone strength was also favourably affected and there was a significant decrease in the loss in vertebral height of the lower thoracic region at the mid-site of the vertebrae.23
Changes to vitamin K intake (from diet and/or supplementation) may interfere with the action of warfarin and other vitamin K antagonists.24