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Vitamin K can be found in two different forms: vitamin K1, also called phylliquinone, and vitamin K2, also known as menaquinone. Here, we reference research on vitamin K2. Menaquinones are present in very small amounts in western diets. Luckily, they are produced by bacteria in the human gut. Vitamin K2 plays a special role in your body, in circulating calcium to your bones and teeth and away from your arteries. Vitamin K2 inhibits arterial and soft-tissue calcification by stimulating matrix Gla protein.
Post-menopausal women, who have the highest rate of osteoporosis, were selected for a 2009 clinical study on the effects of Vitamin K on bone health. 244 healthy postmenopausal women were given 180mcg per day of vitamin K2 or a placebo for three years, and their bone strength and density was measured each year. Vitamin K2 reduced age-related decline in bone mineral content and bone mineral density at the lumbar spine and femoral neck, but not at the total hip. Bone strength was affected positively by vitamin K2 and a decrease in the loss of vertebral height in the lower thoracic region was found.
In a 1991 study, blood samples were taken from two groups in order to review the levels of vitamin K2. The subjects in the first group had osteoporosis and had experienced a recent fracture; those in the second group were healthy and did not have osteoporosis. Vitamin K2 levels were significantly higher in the group without osteoporosis. In the osteoporosis group, only two of the 29 patients were getting sufficient levels of vitamin K2.
Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women.
Knapen MH, Drummen NE, Smit E, Vermeer C, Theuwissen E., Osteoporosis International, 2013
Depressed levels of circulating menaquinones in patients with osteoporotic fractures of the spine and femoral neck.
Hodges SJ, Pilkington MJ, Stamp TC, Catterall A, Shearer MJ, Bitensky L, Chayen J., Bone, 1991
Vitamin K2 supports heart health by stimulating Gla-protein in order to prevent calcification of the arteries and soft-tissue. Clinical studies have attempted to further prove the benefits of vitamin K2 for heart health.
16,057 women who were free of cardiovascular disease were analyzed using a food frequency questionnaire. After approximately 8 years there were 480 cases of cardiovascular heart disease (CHD) in the group. The average daily vitamin K2 intake for the patients who developed CHD was 29.1mcg, far below the recommended daily intake of 80mcg/day.
A 2004 study also reviewed vitamin K2 intake and its relation to CHD. The Rotterdam study reviewed the dietary intake of 4,807 subjects. They found the relative risk of CHD mortality and severe aortic calcification was reduced in the middle and upper tiers of vitamin K2 consumption when compared to the lower tier.
A 2015 clinical study attempted to prove a link between vitamin K2 and arterial stiffness. 244 healthy post-menopausal women were randomized and given either a placebo or 180mcg of vitamin K2 per day. After three years, the group receiving vitamin K2 showed fewer signs of arterial stiffness than the placebo group when measured using echotracking.
A high menaquinone intake reduces the incidence of coronary heart disease.
Gast GC, de Roos NM, Sluijs I, Bots ML, Beulens JW, Geleijnse JM, Witteman JC, Grobbee DE, Peeters PH, van der Schouw YT., Nutrition, metabolism and cardiovascular diseases: NMCD, 2009
"Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial."
Knapen MH, Braam LA, Drummen NE, Bekers O, Hoeks AP, Vermeer C., Thrombosis and haemostasis, 2015
Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study.
Geleijnse JM, Vermeer C, Grobbee DE, Schurgers LJ, Knapen MH, van der Meer IM, Hofman A, Witteman JC., The Journal of Nutrition, 2004