Recently I restarted taking vit K for various reasons. I immediately noticed that 60-90 minutes after taking it I have more energy. I also saw similar results in Amazon reviews, so I googled it. Sure enough, this is what I have found: https://dailydose.ttuhsc.edu/2016/september/vitamin-k.aspx "Back in the 1950s and 1960s, researchers looked for answers as to how vitamin K2 might interact with mitochondria, which are organelles that supply energy to the body. Now, years later, Reid revisited vitamin K2 in collaboration with Cintergia. Mitochondria use oxygen in body to produce energy. Reid explained that mitochondria were from ancient bacteria taken up by cells eons ago. Remnants of these bacteria now function to produce energy in your body. One of the molecules they produce is Adenosine 5'-triphosphate (ATP), which is the principal molecule for storing and transferring energy in cells. Without mitochondria, you could not lift a finger. “We found that vitamin K2 allows you to make more ATP,” Reid said. “When you measure ATP production you can see the oxygen consumption capacity of a cell. We found that addition of vitamin K2 to cells in culture improved their oxygen consumption ability by 60 percent.” In another collaborative study with the University of North Texas, findings confirmed, when vitamin K2 is added to a human diet, energy capacity can actually go up. The study at North Texas looked at 19 young volunteers and gave them vitamin K2 supplements for 6 weeks. When the volunteers were then tested, their cardiac output improvement was equivalent to 6 months of extensive physical training. In this study, participants were given vitamin K2 supplements. But Reid said other sources for vitamin K2 include aged cheeses, organ meats like chicken liver, salami and egg yolks."