Vitamin K2

Vitamin K2, also known as menaquinone, is a fat-soluble vitamin that plays a crucial role in several physiological processes, primarily blood coagulation, bone metabolism, and cardiovascular health. It is one of two main forms of vitamin K, the other being vitamin K1 (phylloquinone), predominantly found in leafy green vegetables. Vitamin K2, however, is found in fermented foods, animal products, and is also produced by bacteria in the human gut. Within the vitamin K2 family, there are several sub-types, designated as MK-n, where 'n' represents the number of isoprenoid residues in the side chain. The most well-researched and common forms are menaquinone-4 (MK-4) and menaquinone-7 (MK-7). MK-4 is found in some animal products, such as meat, eggs, and dairy, and its presence in tissues is partly due to conversion from K1. MK-7, on the other hand, is primarily found in fermented foods, with natto (a traditional Japanese fermented soybean dish) being a particularly rich source. MK-7 has a longer half-life in the body compared to MK-4, which allows for more stable blood concentrations and potentially greater bioavailability and biological activity. This has led to MK-7 being a common form used in dietary supplements (NIH Office of Dietary Supplements). The primary function of vitamin K in the body is to act as a cofactor for the enzyme gamma-glutamyl carboxylase (GGCX). This enzyme is essential for the carboxylation of specific glutamic acid residues in certain proteins, converting them into active forms. These vitamin K-dependent proteins (VKDPs) are critical for processes like blood clotting (e.g., prothrombin) and calcium metabolism (e.g., osteocalcin and matrix Gla protein).