Effects of calcium phosphate citrate on calcium balance in rats

The utility of calcium phosphate citrate (CPCa), which is a new calcium (Ca) material, as a source of Ca was tested on growing rats. Four-week-old male rats (Fischer 344 strain) were divided into four groups and given experimental diets for 33 days. These diets contained one out of two kinds of Ca sources [calcium carbonate (CaCO3) or CPCa] and one out of two Ca levels (normal or high). Thus, there were four diets: CaCO3 and a normal Ca level diet (Ca-group), CaCO3 and a high Ca level diet (HCa-group), CPCa and a normal Ca level diet (CPCa-group), and CPCa and a high Ca level diet (HCPCa-group). There was no difference between the Ca-group and the CPCa-group on growth, Ca balance, serum Ca concentration, kidney Ca accumulation, and femur Ca content. In the HCa-group, food intake decreased and body weight gain was suppressed. Ca absorption in the HCa-group was higher than that in the HCPCa-group, but Ca retention was not different between these two groups. In other words, to adjust to the high-Ca diet, the HCa-group increased the level of Ca excretion in urine, and the HCPCa-group increased the level of Ca excretion in feces. Moreover, the amount of kidney Ca in the HCPCa-group was higher than that in the other groups. These results showed that during normal Ca intake, CPCa was absorbed and used in the body in the same way as CaCO3. When CaCO3 as a source of Ca was consumed in excess, adverse effects manifested as a food intake reduction and body weight gain suppression. In contrast, excessive ingestion of CPCa did not have the adverse ef fects of excess consumption of CaCO3, although kidney Ca accumulation tended to increase.