Something that many may not be aware of:
Increased levels of vitamin D require increased levels of vitamin K, especially of vitamin K2 (menaquinone). Without enough vitamin K2 there is an increased risk of hardening of the arteries and other soft tissues. Vitamin K, along with vitamin D, are essential for the bones to uptake and incorporate calcium.
And this also:
The Calcium Paradox
Vitamin D3 (the natural form of vitamin D) is required for the absorption of minerals in the body, including calcium.
Vitamin K2 is required to direct these minerals to the right place in the body, preventing the inappropriate calcification of the soft tissues
A number of clinical trials have shown that the combination of vitamin K2 and vitamin D3 is more effective in preventing bone loss than either nutrient alone, and there is overwhelming evidence that the safety of vitamin D is dependent on adequate levels of vitamin K2:
-- Without vitamin K2 to complement vitamin D3, calcium may go to the arteries instead of the bones.
Vitamin K2 has been linked to a decrease in atherosclerosis and coronary heart disease, due to its ability to decrease serum cholesterol and reduce cholesterol deposits and calcification in the aorta.