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Fluctuations in international normalized ratio values are often ascribed to dietary changes in vitamin K intake. Here we present a database with vitamin K1 and K2 contents of a wide variety of food items. K1 was mainly present in green vegetables and plant margarins, K2 in meat, liver, butter, egg yolk, natto, cheese and curd cheese. To investigate the effect of the food matrix on vitamin K bioavailability, 6 healthy male volunteers consumed either a detergent-solubilized K1 (3.5 µmol) or a meal consisting 400 g of spinach (3.5 µmol K1) and 200 g of natto (3.1 µmol K2). The absorption of pure K1 was faster than that of food-bound K vitamins (serum peak values at 4 h vs. 6 h after ingestion). Moreover, circulating K2 concentrations after the consumption of natto were about 10 times higher than those of K1 after eating spinach. It is concluded that the contribution of K2 vitamins (menaquinones) to the human vitamin K status is presently underestimated, and that their potential interference with oral anticoagulant treatment needs to be investigated.
Schurgers et al. (Sat,) studied this question.