The calcium and phosphorus in the blood (and human milk) does not precipitate out. These minerals are maintained in human milk at fairly constant levels regardless of maternal diet. Precipitates occur in parenteral solutions because of a variety of factors (i.e., amino acid concentration, pH, temperature). Although I'm not a biochemist, I would think the form that these minerals occur in human milk vs. parenteral solutions effects solubility. Nancy Hurst, RN, MSN Texas Children's Hospital