Vitamin K2 (menaquinones) is a slightly lipid soluble vitamin produced by the helpful microbe of intestines. It is a derivative of naphthoquinone and has similar biological activities as phylloquinone. More importantly, it is one of the indispensable and important vitamins in human body.

　　There are total 14 forms of vitamin K2 (usually noted as MK), which are MK-4, MK-7, MK-8, MK-9, etc. Among them, the synthetic MK-4 and natural MK-7 are the most common forms of vitamin K2. Both of them play important roles in bone and cardiovascular health.

　　The bioactivities of vitamin K2 are related to the length of its side chain. The longer the side chain is, the higher the biological activities are. Vitamin K2 with long side chain is also easier to be absorbed and can exists in the blood for a longer time. Vitamin k2-7 (MK-7) is the most unique in the vitamin K2 family and has been proved to have the highest bioavailability. It has a long half-life in the blood after oral intake, thus it can play its benefits for a long period of time.

The structure of vitamin K2-7

　　The safety of vitamin K2 has long been recognized by many countries and organizations such as FDA and EU. At present, vitamin K2 has been widely used in many countries and regions as food additives or nutritional supplements.

　　The health benefits and safety of vitamin K2-7 have been approved by Food and Drug Administration (FDA) of American. Statistics from the World Health Organization (WHO) show that vitamin K2, especially the long-chain vitamin K2 represented by vitamin K2-7, is recognized as a high-quality natural vitamin K2. In 2008, the European Food Safety Agency (EFSA) published positive scientific opinions on vitamin K2-7 that extracted from natto, as a dietary supplement and food additive. In 2009, an evaluation taken by the European Food Safety Commission recognized vitamin K2's claim of reducing bone loss and improving bone integrity, then vitamin K2-7 from natto has been approved as a new resource food. China also officially approved vitamin K2 as a nutritional fortification supplement to be included in the national nutritional fortification catalogue (14880) in 2016.