Intervention Study on the Effect of Vitamin K2 (Menaquinone-7) Supplementation on the Vascular Stiffness in Subjects With Poor Vitamin K-status

This study will be a double-blind randomized placebo-controlled intervention study. In total 240 healthy men and women between 40 and 70 years will be recruited in the province of Limburg through small advertisements in local newspapers. Eligible participants will be randomized into 2 study groups: * Group 1: MK-7 (1 tablet: MK-7 dosage is 180 μg) * Group 2: Placebo (1 tablet: MK-7 dosage is 0 µg) Each group will consist of 120 participants. A double-blind design is chosen to avoid the occurrence of bias during the study. After randomization, the participants consume the placebo or MK-7 tablets once daily with either breakfast or dinner during one year. People who are interested to participate will come to the research laboratory of VitaK for a screening visit (day -14). During this visit, the investigator will check whether the volunteers are eligible for inclusion based on the in- and exclusion criteria. After meeting the inclusion criteria and none of the exclusion criteria, volunteers will be assigned a randomization number from a computer-generated randomization list. A stratified block randomization will be performed for gender, in order to avoid unequal distribution of men and women among the 2 treatment groups. On-site measurements will be performed at t=0 and after 1 year of treatment: the carotid-femoral Pulse Wave Velocity (cfPWV; primary outcome) and echotracking of the common carotid artery to assess the vascular stiffness (secondary outcome). A Whole Body scan with DXA will be performed to determine total fat and lean mass of the participants. Blood will be taken after an overnight fasting period at t=0 and after 1 year to measure the circulating level of inactive MGP. Results from our previous study (NCT00642551) showed significant changes in vascular characteristics, pulse wave velocity after a 3 year intervention period with a daily dosage of 180 µg MK-7 in 240 postmenopausal women. After 1 year MK-7 intervention inactive MGP levels (improvement of vascular vitamin K status) were decreased 50% compared to placebo and remained at this level during the following 2 years of intervention. Recently published population-based studies show that the unfavorable cardiovascular outcomes are mainly attributable to those within the highest quartile of circulating dp-ucMGP. We expect, therefore, that an intervention study among preselected subjects with poor vascular vitamin K status (inactive MGP levels > 400 pmol/L) and treatment with the same dosage MK-7 (i.e. 180 µg/day) during one year will have a more pronounced effect on arterial stiffening and pulse wave velocity. The follow-up study will be performed at the end of the intervention period of 1 year, with participants who have completed the one year intervention study. From this study population eligible participants (men and women) will be selected. In total 100 participants will be invited. Measurements will be performed at the same day: the carotid-femoral Pulse Wave Velocity (cfPWV), echotracking of the common carotid artery to assess the vascular stiffness and accelerated plethysmography measurements (APG) will be assessed using an fingertip oximeter StiffnoGraph (Taiwan): heart rate, SpO2 (oxygen saturation) and stiffness score.