Commonly it's said that calcium carbonate should be taken with food for it to absorb properly from the acid, but this study shows it absorbs properly without food. 500mg elemental (1250mg) absorbs well. also this study shows optimal timing for people trying to keep parathyroid hormone low due to concern with calcification of soft tissue or reversing bone loss.
They gave men 500mg x2 or 1000mg elemental calcium from a calcium carbonate supplement, on an empty stomach. Looking at the chart & table both 500mg doses and 1000mg doses dramatically lowered parathyroid hormone starting soon after intake
(they gave small amounts of vitamin D with the calcium - wonder if this had any acute effect on absorption? would assume overall serum levels of D would be the thing that influences absorption instead of acute intake of 400iu doses)
Going by this (assuming also getting enough vit a+k1 or k2 mk4 to carboxylate calcium binding protein well), getting 500mg elemental calcium every 4 - 6 hours is good timing for ensuring PTH stays low. empty stomach will work well if tolerated & preferred. parathyroid hormone goes back to baseline/elevation by hour 7 without an additional amount of calcium.
Last edited:
