Rats on prebiotics had significantly higher amounts of cecal contents and lower pH in cecal and colonic contents. Their calcium balance tended to be increased (p b 0.1). Synbiotics reduced pH in different intestinal segments, significantly in cecum.They stimulated most the colonic absorption surface as indicated by colonweight. Only feeding synbiotics significantly prevented OVX-induced loss of calciumcontent in lumbar vertebrae (mg) with final values (mean±SD) of 44.44± 2.94 (SHAM), 41.20±4.59 (OVX), 41.63 ±3.78 (PRO), 43.42±3.07 (PRE), and 44.68±2.28 (SYN).This effectwas associatedwith higher counts of bifidobacteria in the short-termand Bacteroides in the long-term,and with a tendency for lower BAP with 128.7 ± 28.5 U/L vs. 155.3 ± 28.1 U/L in OVX (p b 0.1).