Just one more area that needs more research. I was amazed that my new endocrinologist was thrilled to hear I was already taking K2, as well as Magnesium. I was impressed with a doctor who had some nutritional knowledge! He didn’t seem to care which one I took. I tried MK7 at first, because it was cheaper and had a longer half-life, but I am one of those few people who experienced palpitations with it. I am prone to those anyway, so it likely doesn’t bother most people. I settled on MK4, and the only brand I could find at the health food store was Carlson. I take two tablets a day, each 5 mg for a total of 10. I know the Japanese study was with 45, but I tend to under-dose with most things. I take the morning one with my D3 and the evening one alone with dinner. Was confused about whether or not to take them together in case they compete, so I do take the middle road on that as well.