The first issue is most calcium products are ground up sea shells, (calcium carbonate), or poorly absorbed products that can be sold as calcium (calcium citrate). The second issue you have to be able to absorb it which comes through healthy stomach acid. The third factor comes in as omega 3 fatty acids, the forth issue comes through the health of the thyroid and iodine, the last issue involves your livers health. It is not just calcium it is a function of biochemistry.