Vitamin K helps prevent osteoporosis.

  Low vitamin K intake is associated with bone loss and fractures in people with osteoporosis. And some research suggests that chronic warfarin, a vitamin K antagonist, decreases bone density.

  Several studies suggest that supplementation with a specific form of vitamin K called menaquinone might increase bone density and reduce the risk for fracture.

  But all of the fracture data comes out of Japan. And there is no reliable evidence that taking the form of vitamin K available in the U.S. and Canada, phytonadione, can reduce fracture risk.