Weston A Price was a Dentist, who didn't know why there were so many people with bad teeth. He took on a world trip to find out people who did not have bad teeth. He wanted to find out what can be done to enhance the quality of teeth. He discovered many natives and tribes that had excellent jaw structure and teeth. He discovered the dietary practices of these people, and distilled the knowledge to come up with fish oil and butter oil (ghee) as the two ingredients that can provide the basic necessities for recovering and building teeth and skeletal structure. At that time it was known that Vitamin A was the crucial factor which helped and was obtained from fish oil. The factor from Ghee was not known, and Dr. Price called it Activator X. Vitamin K2 was discovered in 1993, and is now expected to be the Activator X.
Vitamin K comes in 2 forms K1 and K2 and have quite a bit overlapping functionality. K2 seems to have a high effect on forming bones and teeth. K1 reduces the requirement of K2 a lot, so it is also a good idea not to concentrate solely on K2, as K1 is easier to obtain through natural sources.
Vitamin K1 is created by the gut bacteria from elements in green vegetables. Some people may be able to create K2 as well as K2 is also created by bacteria. But the real trouble is that most of the creation happens in the colon, where it is not absorbed. This is the same problem with Vitamin B12. Still it is beneficial to eat plenty of green vegetables.
Vitamin K2 comes in two forms, MK4 and MK7. The MK4 has a very short half life, and is gone within a few hours. MK7 is the storage form and persists for several days. MK4 is made by mothers in their mammary glands, which is an important source of Vitamin K for the newborn children. MK4 is converted to MK7 by bacteria.
Milk from Cows or Buffaloes, which eat green grass have MK4 form in their milk. It is heat stable and ghee from pastured cows is a good source. Long aged cheeses created from pastured cows milk contains a lot MK7. Actually the MK7 content of Cheese is much higher than in ghee. Natto a Japanese condiment made by fermenting soy, is the largest source of MK7, and is used in MK7 supplements.
Green Vegetables, Ghee, and aged Cheeses are a good way to get the full spectrum of vitamin K. But since most of the milk these days is not pastured, and our gut bacteria are not in the best of health, so Vitamin K2 content may still be lacking, particularly for people with impaired gut.
Super K from Life Extension is a good supplement which contains all three varieties. MK4 in supplements is normally synthetic, which may contain some trans version of MK4, and maybe problematic. So it is still better to try and get the vitamin from pastured dairy. Several Pastured butters and cheeses are available from Europe and Australia. The supplement is also quite expensive, but imported butter and cheeses in India would be prohibitively expensive.
Update: Be aware that Vitamin K2 does not work well with Blood thinners like Warfarin, which are actually Vitamin K antagonist. Vitamin K is very important for our body and Warfarin can cause quite a bit of side effects, including osteoporosis, due to this effect. IMO a better option is to use mega doses of Omega3s, which will suppress Omega6 signalling and act as an anti-coagulant.
Updated2: Vitamin K2 requires several cofactors to do its job, some of them are Vitamin A, Vitamin D, Magnesium. It also helps with the uptake of Vitamin D and Sulfates.