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

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Abstract
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.