Review supports K1 and K2 having separate recommended daily intakes

The differences between vitamins K1 and K2, pertaining to recommended daily intake, have been reviewed by Norwegian nutritional experts

Differences between vitamins K1 and K2 have been examined in a new paper by NattoPharma’s International Research Network. The paper assesses the need for a vitamin K2-specific recommended daily intake (RDI). Recognising the importance of a vitamin K2-specific RDI, is an endeavor NattoPharma is currently spearheading with the help of its research partners.

According to the authors, the paper is the first to highlight differences between isoforms vitamin K1 and K2 by means of the source, function, and extrahepatic activity.

The paper explains that based on its very molecular structure, K2 is available beyond the liver to support systems like the bone and vasculature through proper calcium utilisation. Significantly different from K1.

Expert opinions

Presenting the findings, Prof Schurgers, co-author and Professor of Biochemistry of Vascular Calcification said that although functions of K2 are proving to be beneficial with regard to cardiovascular diseases and bone metabolism, there is a growing body of evidence suggesting vitamin K2 is involved in multiple cellular processes. Therefore it might have a protective role in various organs throughout the human body.

As Professor of Biochemistry of Vascular Calcification and Vice Chair of Biochemistry at the Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Schurgers is of the opinion that the functions are different enough that it would, and should, influence the RDI.

“When exploring the non-coagulation, extrahepatic activities of vitamin K, it is clear that K2 in its various forms is the highlight of such activity. Therefore, although history and nomenclature have classed K1 and K2 into the same category, these molecules can have a very different action in the body,” said Schurgers.

The senior author and leader of the research project, added: “Major health organisations, such as WHO, European Food Safety Authority (EFSA) and FDA have established RDI for vitamin K, which is solely based on the dose of K1 to retain an appropriate blood clotting function. Differences between K1 and K2 merit recognition among national and international regulatory organisations, and remain open to research.”

Dr Hogne Vik, Chief Medical Officer at NattoPharma, said: “This review paper continues to explore the differences between Vitamin K1 with its known benefit for coagulation and the newly recognised benefits of Vitamin K2 also to function extrahepatically to support bone and cardiovascular health.”

Vik added: “Practically, the body of evidence today supports a dominant role for Vitamin K2 in the inhibition of calcification of soft tissues because of its better bioavailability and bioactivity. Observational studies and gold standard double-blind, placebo-controlled trials show that Vitamin K2 may inhibit vascular calcification and even hold progression of vascular stiffness.”

The Chief Medical Officer echoed Schurgers plea for vitamin K2 to be distinguished from its sister vitamin, for an individualised RDI. Citing K2’s elucidated inhibition of vascular and soft tissue calcification as a core reason.

The grant

The review is the result of the Intricare and EVOluTION grants, awarded to NattoPharma’s International Research Network by the EU, within the Horizon 2020 Marie Skłodowska-Curie research and innovation programme.

The programme trained a total of 26 Early Stage Researchers, focusing on harnessing endogenous mechanisms for health and the effect of vitamin K to hold or regress microcalcification and subsequent cardiovascular disease.

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