Vitamin K is commonly known as an essential factor in making sure our blood clots, to help wounds heal properly. Vitamin K is also a vital cofactor in the carboxylation (a specific chemical reaction) of osteocalcin, a protein released by osteoblasts during bone formation. Once vitamin K initiates carboxylation, osteocalcin can then help guide calcium into bone (and not into soft tissues where it can harden blood vessels), increasing bone density and acting as a tempering agent keeping bone flexible and less prone to breaking
There are two major types of K.
Vitamin K1 (phylloquinone) comes from leafy green vegetables like kale, chard and spinach. While it is a capable cofactor for carboxylating proteins, it is better suited for making blood clotting factors in the liver.
Vitamin K2 (menaquinones) has an easier time traveling throughout the body and into places such as bone, so ingesting K2 is the better type for affecting bone health. Of the dietary sources of vitamin K2, the two most related to bone health are MK4 and MK7. MK4 comes from meats (especially organ meats such as liver), eggs and hard cheeses; it may act somewhat more broadly in its activity, but it has a half life of only an hour or so. MK7 comes from fermented soy and has a much longer half life, which would ensure a more thorough and steady carboxylation capacity. As far as bone health is concerned, it may be best to use a combination of these forms of vitamin K2 but the jury is still out as far as how to achieve optimal skeletal benefit from vitamin K.
A three-year study from The Netherlands investigated the effects of vitamin K2 MK7 supplementation in healthy postmenopausal women (n=244). The results, published in Osteoporosis International, demonstrated that 180 mcg oral supplemental vitamin K2 MK-7 per day was beneficial to bone. “MK-7 intake significantly improved vitamin K status and decreased the age-related decline in BMC [bone mineral content] and BMD [bone mineral density] at the lumbar spine and femoral neck, but not at the total hip. Bone strength was also favorably affected by MK-7. MK-7 significantly decreased the loss in vertebral height of the lower thoracic region at the mid-site of the vertebrae.”
There is no doubt this is an important study and one that helps establish K2 MK7 as a valuable supplement for individuals focused on keeping their bones healthy.
That said, we must keep in mind that this study was performed on HEALTHY postmenopausal women. For individuals who have a metabolic disease such as osteoporosis, simply adding therapeutic levels of vitamin K may not result in the same level of benefit. Reversing substantial bone loss usually takes promoting change throughout all aspects of the person’s physiology: adequate levels of vitamins K and D, a healthy gut that can absorb nutrients, a reduction in chronic inflammation causing oxidative stress, and a body pH that is not acidic. These and a host of other physical factors for whole-body health and thus bone health must all be assessed and corrected if possible.
Knapen, M.H., et al. 2013. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. March 23 [Epub ahead of print].