Iīm not sure.. but I do know that prolongued use of tums, rolaids, etc... might develop in hypercalcemia... and turn into stones.. (bladder or something)

also if a multivitamin has already 100% of USRDA... not sure but i donīt think you should stop eating "x" thing because it also has vitamin D... just like with orange juice if you drink a glass an it supposedly has, I donīt know, letīs say 60 % vitamin C but you also took a tablet of Vit C with 100% USDRA... then the extra just gets out of your system via urine, etc... but not sure how vit. D works...