Effects of high compared with low calcium intake on calcium absorption and incorporation of iron by red blood cells in small children.

BACKGROUND: The potential benefits of increasing calcium intake in small children must be balanced with the potential risk to iron utilization from high calcium intakes. OBJECTIVE: This study was designed to evaluate the relation between calcium intake and calcium absorption and iron incorporation into red blood cells. DESIGN: We performed a multitracer, crossover study of the absorption of calcium and red blood cell incorporation of iron in 11 preschool children aged 3-5 y who had been adapted for 5 wk to low- (502 +/- 99 mg) and high- (1180 +/- 117 mg) calcium diets. Stable-isotope studies were performed by using 44Ca and 58Fe given orally with meals and 46Ca given intravenously. RESULTS: Iron incorporation into red blood cells 14 d postdosing was similar (6.9 +/- 4.2% compared with 7.9 +/- 5.5%; NS) with the low- and high-calcium diets, respectively. Total calcium absorption (181 +/- 50 compared with 277 +/- 91 mg/d; P = 0.002) was greater in children with the higher calcium intake. CONCLUSIONS: Our findings indicate that small children may benefit from calcium intakes similar to those recommended for older children without adverse effects on dietary iron utilization.