To maximize absorption, take no more than 500 mg of elemental calcium at one time. (lpi.oregonstate.edu)
I have a huge fear of osteoporosis and I take store - brand calcium citrate (elemental calcium + D3) twice per day. (wellnessmama.com)
As for the sources, countless people all over the world are taking isolated elemental calcium for their bones, but new evidence is now pouring in to suggest that they'd be better off improving their diets instead. (supernaturalacnetreatment.com)