The objective of the SAFE K study is to demonstrate that in patients treated with the antagonists of vitamin K (VKA), a daily intake of vitamin K2 (75 micrograms/day) as naturally produced by the ferments used in fermented dairy products, does not upset the balance of anticoagulant treatment.Fifty-two patients will be chosen to receive either verum or placebo for four months after a 4-month run-in period.In addition, the study evaluates if regular consumption of vitamin K2 reduce the need of changing the dose of anticoagulation treatment and improve the markers of bone mineralisation.