However a higher Vitamin D intake also requires a matching higher calcium intake since high Vitamin D levels with calcium deficiency can worsen existing bone density problems. This can be due to the potential serum calcium-raising effect of supplemented Vitamin D by absorbing calcium from whatever available sources, including bone, as a result of calcium being insufficiently present in the intestine from dietary sources. This does not apply to any amounts of Vitamin D generated from sun UVB exposure... Full Text