In the first human study using natural vitamin K2 as a dietary supplement it was demonstrated that natural menaquinone-7 was significantly better as compared to the synthetic vitamin K1 in several important areas, including better absorption.

The study showed that despite their different lipophylicity, maximal serum concentrations of K1 and MK-7 were seen at approximately 4 hours after intake. But at the same time, MK-7 absorption was 1,5 fold better than K1. A marked difference was observed during the second phase (between 8 and 96 hours after mealtime), in which K1 declined to its baseline within several hours, whereas MK-7 remain detectable for at least four days.

 Absorption K1 vs K2

Circulating vitamin K concentrations following a single oral dose of 1mg each of vitamin K1 (orange) and vitamin K2-MK-7 (green) [13].

The difference between these two vitamins may be related to the fact that following intestinal absorption, both are taken up in the triglyceride fraction from which rapidly cleared by the liver but that only higher menaquinones are redistributed via low density lipoproteins (LDL) [14].