Natural Factors Vitamin K & D - 120 mcg of K2 & 1000 IU of Vitamin D3 - Helps improve bone health and prevents arterial calcification. Vitamin K has been found to help direct calcium to the areas of the body where it is needed, such as the skeleton, and away from areas where it could have a negative effect, such as the cardiovascular system. Vitamin D is critical for the proper metabolism and absorption of calcium in the bones, and Vitamins K and D have been shown to work synergistically to improve bone density.