Effects of excess calcium as a different form on mineral metabolism in rats

Excess calcium is known to affect the metabolism of other minerals. Calcium carbonate is the main source of calcium used in previous experiments that investigated excess calcium. Thus, it remains to be clarified whether other forms of calcium also have the same adverse effects. The effects of a high‐calcium carbonate diet or a high‐calcium citrate diet on mineral concentration in several tissues of rats were examined. Male rats aged 5 weeks were fed one of the experimental diets for 4 weeks. The control diet contained calcium as calcium carbonate at the requirement level. High‐calcium diets contained calcium carbonate or calcium citrate at a level of fivefold greater than the requirement level. In rats fed the high‐calcium diets, a similar decrease in phosphorus (in the plasma) and iron (in the testis, liver and femur) was observed. Hepatic copper increased in rats fed the high‐calcium diets, whereas renal copper decreased. Therefore, excess calcium affects these mineral metabolisms regardless of its form. In contrast, the high‐calcium carbonate diet increased femoral zinc and decreased femoral magnesium, but the high‐calcium citrate diet did not affect these minerals in the femur, which suggests that the effect of excess calcium on minerals partly depends on its form.