Vitamin K
Calcium and vitamin D are important mediators in bone growth, but vitamin K plays an equally important role. The synthesis of bone growth is dependent on vitamin K, through its carboxylation of osteocalcin, a protein secreted by osteoblasts. Osteocalcin guides calcium into bones and prevents its absorption into organs, joint spaces and arteries. Vitamin K occurs in three main forms: K1 (phylloquinone), found primarily in the liver, naturally occurs in green leafy vegetables and is considered to be the main dietary source; K2 (menaquinone), which is a group name for a family of related compounds differentiated by their side chains; and K3 (menadione), which does not have vitamin K activity.
MK-4 and MK-7 are the two subclasses of K2 most widely studied for their role in bone and cardiovascular health. MK-4 is primarily a metabolic byproduct of K1 while MK-7 is found in small quantities in liver mitochondria and other tissues. The MK-7 form is substantially more active, has a longer half-life and accumulates to higher concentrations in serum than vitamin K1. The different degrees of bioavailability between K1 and K2 are due to differences in structure. The long side-chain of vitamin K2 (specifically MK-7) allows it to bind with fat particles in circulation. This process then allows easier facilitation to soft tissue, bones and arteries. More recently, research has shown that doses of 180 mcg of MK-7 provide greater results when supporting both bone and cardiovascular health.
Vitamin K Depletion
Although most people consume adequate dietary levels/amounts of vitamin K to maintain sufficient blood clotting, most do not consume enough MK-7 to meet cardiovascular and bone health needs. Compromised intestinal absorption can also lead to insufficient K2 levels, leaving calcium available to be exported out of bone and into other tissues. Other medications such as antibiotics, cholesterol-lowering medications and laxatives have also been found to contribute to a vitamin K deficiency.
Bone Health
Supplementation of K2 has repeatedly been shown to help maintain bone density and strength among women. Research from Japanese populations has found superior bone health among women who more frequently consumed MK-7 rich nattō than those who did not.12 The positive effect of K2 on bone health is also evident among healthy children, among whom modest supplementation with MK-7 has been shown to increase osteocalcin carboxylation. In a randomized, placebo controlled trial, 180 mcg of MK-7 or placebo were given to 244 healthy post-menopausal women over the course of three years. After at least two years, statistically significant benefits were seen in vertebrae, hip and femoral neck. Another ground-breaking randomized, placebo-controlled trial gave 244 women, aged 55-65, 180 mcg of vitamin K2 or placebo. The study found that those given the K2 were significantly better able to maintain their osteoclast to osteoblast ratio. Furthermore, levels of circulating osteocalcin, a marker related to tissue calcification in the body, were reduced by 50% among women taking K2 versus a 4% increase among the placebo group after two and three years.
Cardiovascular Health and Blood Sugar Balance
Vitamin K also plays a key role in supporting the cardiovascular system and healthy blood sugar balance. In a large population study, those who consumed high amounts of K2 had significantly improved cardiovascular markers compared to those given vitamin K1. A cohort of over 16,000 women also linked higher intake of K2 with better maintenance of cardiovascular health. Studies have also shown vitamin K to support healthy blood sugar metabolism. Doses of 180 mcg of K2 have been shown to have a positive effect on arterial and vascular elasticity. Additionally, 180 mcg of K2 given over two to three years has been shown to help maintain soft tissue health and vascular elasticity in healthy adult subjects.17 The same amount of MK-7 was also found to impart substantial benefits in arterial plasticity and blood vessel elasticity in healthy women, which had previously been only with “pharmacological doses” of synthetic vitamin K of up to 4,500 mcg daily.
Triage Theory
The Triage Theory states that in the face of nutrient inadequacies, nature ensures short term survival of a cell is protected at the expense of long term consequences. Vitamin K is an excellent example of this theory. Hypothetically, a short-term deficiency in vitamin K would lead to a reduction in blood clotting. This direct threat to survival does not happen, as the body uses its metabolic reserve of vitamin K to ensure immediate needs are met. If continued, this dip into reserve leads to a long term deficiency in vitamin K. Though not directly threatening immediate survival, long-term deficiencies are linked to bone fragility, arterial calcification and genomic instability. These issues are related to a loss of vitamin K-dependent proteins not required for short-term survival, nevertheless presenting long–term health challenges.
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