If you go back to the link I gave you https://www.nutritionadvance.com/vitamin-k2-benefits/ , here are some key points:
There are many different forms of vitamin K2, but the two primary forms found in food are:
Menaquinone-4 (MK-4): animal foods such as dairy and meat contain MK-4.
Menaquinone-7 (MK-7): the best source of MK-7 is natto, a traditional Japanese fermented soy product. Other fermented soy dishes also have very high concentrations of MK-7.
On the other hand, vitamin K1 (phylloquinone) mainly occurs in plant foods, predominantly in dark green vegetables such as collard greens and spinach.
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As previously mentioned, we can get vitamin K from K1 (mainly green vegetables) and K2 (animal foods and bacteria/fermented food sources).
With this in mind, one of the most significant benefits of vitamin K2 is that the MK-7 form (found in natto) has greater bioavailability than vitamin K1.
First of all, vitamin K1 has very poor bioavailability, and studies show that K1 absorption may be as low as 4% in foods like spinach.
Since vitamin K is fat-soluble, eating the spinach alongside a source of fat (butter) led to a threefold improvement in the absorption rate.
Although the precise absorption rate of vitamin K2 is not known, the consumption of menaquinone-7 significantly raises serum vitamin K levels.
The graph below (see link for graph) shows that vitamin K2 (MK-7) has a much greater absorption rate and half-life in the body, and keeps vitamin K levels high for several days
Additionally, the Rotterdam Study showed that menaquinone (K2) decreased the risk of arterial calcification and cardiovascular disease mortality. In contrast, phylloquinone (K1) had no such effect ).
Key Point: As evidenced by the absorption rate in numerous studies, vitamin K2 is significantly more bioavailable than K1.
I have been lightly steaming my spinach with a pat of butter on top. I do stir fried green vegies with butter and/or olive oil, so hopefully I will get 12% or higher K1 absorbtion. I bought Savoy Cabbage recently it looked so much darker green than regular cabbage. It was still very tough steamed, so I tried using it in stir fry and liked it better with the other vegies.
A friend gave my partner some bottles of nattokinase. Would this be what you are talking about as natto. He was told it was supposed to enhance the effect of other supplements. Is this correct? What dose would be recommended?