Practitioners and patients are becoming increasingly aware of the benefits of Vitamin K for optimal bone and cardiovascular health. This post will address some commonly asked questions on the various forms of Vitamin K, their benefits, and how best to utilize this important nutrient.
Isn't vitamin K deficiency rare, and associated with bleeding disorders?
Yes and no. A diagnosis of frank vitamin K deficiency is rare, since the definition of the Adequate Intake of Vitamin K is based on the requirement by the liver for synthesis of clotting factors. However, some research points to substantial concentrations of undercarboxylated osteocalcin and extra-hepatic Gla-proteins found in the circulation of non-supplemented individuals, indicating an inadequate amount of the Vitamin K required to carboxylate these proteins. When these levels were measured in 896 samples of healthy volunteers, children and adults over 40 years of age showed the largest tissue-specific vitamin deficiency. (1) Multiple studies have demonstrated that supplementing with a subtype of Vitamin K called Vitamin K2-7 (also known as menoquinone 7 or MK-7) can decrease the circulating levels of these undercarboxylated proteins. (2, 3)
Is there an added benefit to supplementing Vitamin K2-7 along with Vitamin D3 for bone health?
Vitamin D3 helps increase intestinal uptake of calcium, and decrease urinary excretion of this important mineral. In other words, Vitamin D3 helps increase calcium levels in the blood. Vitamin K2 then supports the bones' ability to take up this calcium, by carboxylating the protein osteocalcin in the extracellular matrix of bone. This may help promote bone mineralization.* In one 2013 study, 244 healthy postmenopausal women received MK-7 capsules (180 μg MK-7/day) or placebo daily for 3 years. MK-7 intake significantly improved vitamin K status and decreased the age-related decline in bone mineral density at the lumbar spine and femoral neck, though not at the total hip. MK-7 was also associated with greater bone strength and significantly decreased loss of vertebral height in the lower thoracic spine. Researchers concluded that supplementation with MK-7 may help post-menopausal women prevent bone loss. (4)
What does Vitamin K2-7 have to do with cardiovascular health?
In addition to bone, Vitamin K2-7 also concentrates in the tissues of the arteries, where it carboxylates Matrix GLA Protein, an inhibitor of arterial calcification. Maintaining healthy calcium metabolism in the artery wall helps support vascular elasticity. Healthy, elastic arteries in turn support healthy blood pressure levels and endothelium, by reducing shear stress on the artery wall. Micro-injuries to the endothelium caused by shear stress are thought to be an initiating event in the formation of atherosclerotic plaques in the artery wall. In a 2015 double-blind, randomized,clinical trial , 244 healthy post-menopausal women were randomly assigned to receive either 180 mcg vitamin K2 menaquinone-7 (MK-7) or placebo capsules daily for 3 years. This trial showed substantial benefits in preventing age-related stiffening of arteries as measured by both echotracking and pulse wave velocity (PWV). Researchers concluded long-term use of MK-7 supplements may improve arterial stiffness in healthy postmenopausal women, especially in women having a high arterial stiffness to begin with.(5)
Why choose to supplement Vitamin K2-7 over other forms of Vitamin K? What about getting vitamin K from leafy green vegetables?
Leafy greens, along with all other colorful vegetables, are an essential part of a healthy diet for numerous reasons, including the vitamin K1 they provide. K1 or phylloquinone is involved in synthesis of blood clotting factors as mentioned above. However, studies have not found K1 to have any of the same effects as vitamin K2 in terms of reducing risk of coronary heart disease , coronary calcification, or all-cause mortality (6, 7) Another form of Vitamin K2, vitamin K2-4 (also known as menoquinone 4 or MK-4), has demonstrated benefits as well, but in a study comparing bioavailability of menaquinone-4 and menaquinone-7 in healthy women, researchers concluded that MK-4 did not contribute to the vitamin K status as measured by serum vitamin K levels, while MK-7 significantly increased serum MK-7 levels and may be of particular importance for extrahepatic tissues.(8) In the Western diet, vitamin K2 is obtained mainly from cheese, with smaller amounts from other animal foods including milk and meat. Many people choose to avoid some of these foods for various reasons, but as cited above, even among the general population, many individuals appear to have tissue-specific deficiency of vitamin K2 as measured by undercarboxylated extra-hepatic Gla-proteins.
Is Vitamin K2-7 supplementation safe for everyone?
Because of its role in clotting, Vitamin K supplementation is generally contraindicated for those taking Coumadin/warfarin anticoagulant medication.
DISCLAIMER: The information contained in this article is for informational purposes only, and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
References:
1. https://www.ncbi.nlm.nih.gov/pubmed/24296867
2. http://www.ncbi.nlm.nih.gov/pubmed/23062766
3. http://www.ncbi.nlm.nih.gov/pubmed/22289649
4. http://www.ncbi.nlm.nih.gov/pubmed/23525894
5. http://www.ncbi.nlm.nih.gov/pubmed/25694037
6. http://www.ncbi.nlm.nih.gov/pubmed/15514282
7. http://www.ncbi.nlm.nih.gov/pubmed/18722618
8. http://www.ncbi.nlm.nih.gov/pubmed/23140417
