Vitamin K2

Research published in the April 2012 issue of the journal Calcified Tissue International found that postmenopausal women fed dairy products enriched with 400 IU of vitamin D and 100 mcg of vitamin K2 had improved bone mineral density (BMD) beyond those fed dairy enriched with vitamin D alone. The vitamin K also significantly lowered undercarboxylated osteocalcin and urine deoxypyridinoline, both markers of bone breakdown.

Vitamin K2 is one of my favourite vitamins. Different than the vitamin K1 found in dark leafy greens and vegetables, vitamin K2 is derived from natto, a fermented soy product, and is responsible for activating osteocalcin (vitamin K1 does this to a lesser extent). Osteocalcin is the hormone that promotes calcium deposition in the bones. It also removes calcium from soft tissues such as muscle and arteries. Basically, the main function of vitamin K2 is to tell the calcium where to go. Vitamin D is well known for increasing the absorption of calcium into the blood. However, when someone takes a calcium + D they are simply increasing their blood levels of calcium and hoping that some will get into their bones. The reality is that some will get into the bones and some will get into other less desirable locations in the body such as our arteries as a component of plaque deposits. This is where vitamin K2 comes in. It directs calcium. First it directs it into the bone and promotes bone building. Second it directs calcium out of soft tissues where it is then excreted in the urine.
As mentioned above vitamin K2 is derived from a fermented soy product called natto. Other natural sources are soft cheeses and grass fed animal products, including egg yolk. Unfortunately not much of the meat out there is grass fed, which is why a supplement may be necessary. 
When looking to supplement with K2 it is important to realize that there are two forms MK-4 and MK-7. Both work but at different doses. The average dose used in much of the research showing benefit is 45mg (milligrams) of MK-4 and 120mcg (micrograms) of MK-7. This is especially important to note if you live in Canada because Health Canada limits the dose of any vitamin K (K1, K2 MK-4, K2 MK-7) to 120mcg per capsule. What that means is that to get proper dosing of the MK-4 form in Canada one would have to consume 375 capsules a day. Fortunately most companies use the MK-7 form which works well at the lower dose of one capsule per day.