Vitamin K2 is also called menaquinone, is made by the bacteria that line gastrointestinal tract. K2 is really critical for keeping our bones strong and arteries clear.
K2 can be broken into two additional categories, called MK4 & MK7
MK-4: a short-chain form of vitamin K2 found in butter, egg yolks, and animal-based foods
MK-7: longer-chain forms found in fermented foods like mature cheeses and curd (richest source: Japanese dish natto made of fermented soybeans and Bacillus subtilis)
What is the optimal amount for an adult
The optimal amounts of vitamin K2 is still not very clear but it seems likely that 180 to 200 micrograms of vitamin K2 should be enough to activate your body's K2-dependent proteins to shuttle the calcium where it needs to be and where it is not.