Submitted August 9, 2006
Accepted December 3, 2006
Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7
Leon J Schurgers, Kirsten JF Teunissen, Karly Hamulyak, Marjo HJ Knapen, Hogne Vik, and Cees Vermeer*
VitaK & Cardiovascular Research Institute CARIM, University of Maastricht, Maastricht, Netherlands
Department of Hematology, University Hospital Maastricht, Maastricht, Netherlands
NattoPharma ASA, Oslo, Norway
* Corresponding author; email: c.vermeer{at}bioch.unimaas.nl.
Vitamin K is a cofactor in the production of blood coagulation factors (in the liver), osteocalcin (in bone) and matrix Gla-protein (cartilage and vessel wall). Accumulating evidence suggests that for optimal bone and vascular health relatively high intakes of vitamin K are required. The synthetic short chain vitamin K1 is commonly used in food supplements, but recently also the natural, long chain menaquinone-7 (MK-7) has become available as an OTC supplement. The purpose of this paper was to compare in healthy volunteers the absorption and efficacy of K1 and MK-7. Serum vitamin K species were used as a marker for absorption, and osteocalcin carboxylation as a marker for activity. Both K1 and MK-7 were absorbed well with peak serum concentrations at 4 h after intake. A major difference between both vitamin K species is the very long half-life time of MK-7, resulting in much more stable serum levels and accumulation of MK-7 to higher levels (7-8 fold) during prolonged intake. MK-7 induced more complete carboxylation of osteocalcin and hematologists should be aware that preparations supplying 
50 µg/day of MK-7 may interfere with oral anticoagulant treatment in a clinically relevant way.
