Submitted to: Nutrition and Metabolism
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2012
Publication Date: 2/1/2012
Citation: Fu, X., Moreines, J., Booth, S.L. 2012. Vitamin K supplementation does not prevent bone loss in ovariectomized Norway rats. Nutrition and Metabolism. 9(1):12. Interpretive Summary: Vitamin K exists in two forms in the diet: phylloquinone (PK), which is found in green leafy vegetables, and menaquinones (MKn) produced by bacteria, which are found in some types of cheeses. There has been considerable recent interest in the role of vitamin K in bone metabolism. The European Food Safety Authority recently approved a health claim for MKn and bone health. However, the abilities of PK and MKn to prevent bone loss remain questionable. The objective of this work is to compare the effects of PK and MKn on the rate of bone loss in a rodent model. PK and MKns were found to have no beneficial effect on bone loss. These results are consistent with other studies which show that MKn supplementation had no effect on bone loss in post-menopausal women. These results are important in order to better understand vitamin K’s function related to bone heath. These results are significant because they show the need for future clinical studies in order to provide guidance on which forms of vitamin K are required for optimal human health.
Technical Abstract: Despite plausible biological mechanisms, the differential abilities of phylloquinone (PK) and menaquinones (MKn) to prevent bone loss remain controversial. The objective of the current study was to compare the effects of PK, menaquinone-4 (MK-4) and menaquinone-7(MK-7) on the rate of bone loss in ovariectomized (OVX) Norway rats. A secondary aim was to compare the effects of vitamin K with those of bisphosphonates (BP) on bone loss. OVX rats (n=96) were randomized to 6 dosing groups [n=16/group; Sham OVX; OVX; OVX + BP (100ug/kg/100 ug/mL saline sc); OVX + PK; OVX + MK-4; and OVX + MK-7] for 6 wks. Equimolar daily doses of 107 mg PK/kg, 147 mg MK-4/kg, and 201 mg MK-7/kg diet were provided. BP significantly increased bone strength and bone mineral density (BMD) vs. OVX (P<0.05). However, PK, MK-4 or MK-7 did not change bone strength or BMD compared to the OVX group. Whereas supplementation of PK, MK-4 and MK-7 increased serum and tibia concentrations of each respective form, PK concentrations were consistently higher despite equimolar intakes. In conclusion, PK, MK-4, and MK-7 do not appear to prevent bone loss in OVX rats when administered concurrent with adequate intake of other nutrients.