High levels of protein make an acid condition in the blood, tax the organs which must eliminate the excess, and trigger loss of calcium from the bones. (fullhealthsecrets.com)
So, in effect, more calcium is lost in the urine stream, but may be compensated by less loss of calcium through the fecal stream. (nutritionfacts.org)
As your protein intake goes up, so can your urinary loss of calcium. (whfoods.com)