Vitamin K2 (menaquinones) is found in meat, eggs, and dairy products and is also made by bacteria in the human gut, which provides a certain amount of the human vitamin K requirement.19 Human studies show that vitamin K2 is up to ten times more bioavailable than K1. Vitamin K2 remains biologically active in the body far longer than K1. For instance, K1 is rapidly cleared by the liver within eight hours, whereas measurable levels of K2 (MK-7) have been detected 72 hours after ingestion.20
The Rotterdam Heart Study, a large-scale, well-controlled clinical trial that tracked 4,800 participants for seven years, revealed that participants who ingested the greatest quantities of vitamin K2 in their diet experienced a better cardiovascular condition than people who ingested the least.21 High intakes of vitamin K2 also corresponded to less calcium deposition in the aorta, whereas participants who ingested less K2 were more likely to show moderate or severe calcification. Animal studies suggest vitamin K intake not only blocks the progress of further calcium accumulation, but also induces 37% regression of preformed arterial calcification.22,23
Ideal Forms of Vitamin K2
In recent years, two forms of vitamin K2 have been extensively researched and the findings reveal vastly improved effects compared to K1. The MK-4 form of vitamin K2 is the most rapidly absorbed and is now routinely used in Japan to maintain healthy bone density. MK-4, however, only remains active in the blood for a few hours. The MK-7 form of K2, on the other hand, remains bioavailable to the human body over a sustained 24-hour period and to higher levels (seven- to eightfold) during prolonged intake.10 Both MK-4 and MK-7 have demonstrated remarkable health benefits when studied in human populations.
Low-Dose Vitamin K2 contains the menaquinone-7 form of vitamin K2, which is not metabolized quickly by the liver, thereby making it available to provide a more consistent supply of vitamin K to the body.