The Effect of Excess Calcium on the Iron Bioavailability and Bone Growth of Marginally Iron Deficient Rats

ABSTRACT

This study examined the effect of excess calcium (Ca) on the iron (Fe) bioavailability and bone growth of marginally Fe deficient animals. Two groups of weanling female SD rats were fed either normal Fe (35 ppm) or Fe deficient diet (8 ppm) for 3 weeks. Then each group of animals were assigned randomly to one of three groups and were fed one of six experimental diets additionally for 4 weeks, containing normal (35 ppm) or low (15 ppm) Fe and one of three levels of Ca as normal (0.5%), high (1.0%), or excess (1.5%). Feces and urine were collected during the last 3 days of treatment. After sacrifice blood, organs, and femur bone were collected for analysis. Final body weight and average food intake were not affected by either the levels of dietary Ca or Fe. Low Fe diet significantly reduced the level of serum ferritin, however, for Hb, Hct, and TIBC no difference was shown than those in the normal Fe group. TIBC increased slightly by high and excess Ca intake in low Fe groups. For both normal and low Fe groups, high and excess Ca intakes reduced the apparent absorption of Fe and Fe contents of liver significantly (p < 0.05). Calcium contents in kidney and Femur of rats that were fed high and excess levels of Ca were significantly greater than those of normal Ca groups. However, weight, length, and breaking force of the bone were not affected by increased Ca intakes. Both in control and low Fe groups, high and excess intakes of Ca decreased the apparent absorption of Ca. These results indicate that the excess intakes of calcium than the normal needs would be undesirable for Fe bioavailability and that the adverse effects be more serious in marginally iron deficient growing animals. In addition bone growth and strength would not be favorably affected by high Ca intakes, though, the long term effect of increased Ca contents in bone requires further examination.