provisionnal answer in wait for access to the referred article
According to wikipedia on vitamin K2 and K the European Food Safety Authority set an "Adequate Intakes" at 70 micrograms a day for vitamin K.
Again according to wikipedia, you can get vitamin K2 out of natto.
The use of an "Adequate Intakes" instead of a recommended dietary allowances and no discrimination between K1 and K2 is due to a lack of evidence when they established their standards.
Therefore, to answer your question, I wouldn't panic about vitamin K2 as research is not being conclusive (yet! I'm curious about your article).
In case of doubt/symptoms, go see a doctor.