Vitamin K is a fat-soluble vitamin, but it is unique in that it is not stored in the body. It includes several chemically similar compounds: phylloquinone (K1) and menaquinones (K2). K2 is labelled MK along with a number indicating the number of isoprenoid residues in the chain (e.g. MK-4, MK-7). The best absorbable and most valuable vitamin is K2 MK-7. Due to its structure, it is carried by lipoproteins in the blood and has a half-life of up to 3 days. This allows the body to utilize this vitamin longer. Compared to K1, it is about 7 times more bioavailable. The richest source of this highly absorbable vitamin is natto – a Japanese dish fermented with the help of bacteria. Studies show that, unfortunately, MK-7 blood levels are usually low, so appropriate supplementation may be indicated. This form, unlike the rest, is not as common in food, which is probably why low concentrations may occur. Menaquinone is primarily responsible for the transport of calcium to the bones and prevents calcification of the arteries. It is an indispensable duo together with vitamin D3. It also participates in blood clotting processes.

There are various preparations containing menaquinone available on the market, with different manufacturer declarations. Sometimes important information may be missing, including the form of K2, the source of origin, etc. The only approved form of MK-7 considered safe by EFSA is menaquinone extracted from Bacillus subtilis natto. This form appears in Novel food, a list of so-called novel foods, and its sale must be approved by the European Union. The European company that produces menaquinone according to the guidelines is Gnosis by Lesaffre in Italy. It is the only company in Europe that has approved raw material produced on site, without intermediaries. It contains vitamin K2 in the patented vitaMK7® form in an amount of over 99% as all-trans-menaquinone-7. This is a highly bioavailable form derived from nature. This production occurs without chemical additives, including preservatives and solvents, using fermentation. It complies with the principles of GMP (Good Manufacturing Practice), ISO and HACCP (Hazard Analysis and Critical Control Points). It is characterized by a purity of over 99%, which allows for several years of durability. Even though the compound comes from bacterial fermentation, it has no microbiological contamination.

It has confirmation of purity in certificates, as a designation of:

• gluten free
• lactose free
• GMO free
• vegetarian and vegan
• halal
• kosher

An important issue to consider when choosing a preparation is the chemical form of the compound. Supplements may contain cis/trans forms of synthetic origin. Chemical synthesis is cheaper to produce, but only the trans form is needed and highly absorbable in the body. A Polish study of the menaquinone content in 8 products available on the market showed that most of them contained less K2 than its declared amount, and the cis/trans form predominated. You can protect yourself from not entirely honest practices by choosing a well-labelled product. The patented and EFSA-approved form of K2 provided by Gnosis would be the best. The Gnosis product has been tested and used in various studies, e.g. Bruge F. et al., which showed an increase in the concentration of vitamin K2 in the blood after its consumption with olive oil.

Bibliography:
https://gnosisbylesaffre.com/ingredient/vitamk7/
https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX%3A32009D0345
Brugè F, Bacchetti T, Principi F, Littarru GP, Tiano L. Olive oil supplemented with menaquinone-7 significantly affects osteocalcin carboxylation. Br J Nutr. 2011 Oct;106(7):1058-62.
Szterk A, Zmysłowski A, Bus K. Identification of cis/trans isomers of menaquinone-7 in food as exemplified by dietary supplements. Food Chem. 2018 Mar 15;243:403-409.
Szterk A, Bus K, Zmysłowski A, Ofiara K. Analysis of Menaquinone-7 Content and Impurities in Oil and Non-Oil Dietary Supplements. Molecules. 2018 May 1;23(5):1056.