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Net calcium absorption in premature infants: results of 103 metabolic balance studies
F Bronner1, B L Salle, G Putet
1Department of BioStructure and Function, University of Connecticut Health Center, Farmington 06030.
Insights
Calcium absorption in preterm infants is not enhanced by vitamin D. This suggests a non-saturable absorption route is active in these low-birth-weight infants, independent of vitamin D regulation.
Area of Science:
- Neonatal Nutrition
- Pediatric Gastroenterology
- Calcium Metabolism
Background:
- Low-birth-weight preterm infants often exhibit altered nutrient absorption.
- Calcium is crucial for bone development in premature infants.
Purpose of the Study:
- To evaluate net calcium absorption in low-birth-weight preterm infants.
- To determine the effect of vitamin D supplementation on calcium absorption.
Main Methods:
- A 72-hour balance technique was used to measure net calcium absorption.
- 103 preterm infants were studied at approximately 3 weeks of age.
- Infants were fed either specialized formulas or banked human milk, with varying supplementation.
Main Results:
- Net calcium absorption averaged 58% with a calcium intake of 80 mg/kg/day.
- Neither vitamin D supplementation nor combined vitamin D and calcium supplementation significantly affected calcium absorption.
- Calcium absorption showed a linear relationship with intake, indicating a nonsaturable process.
Conclusions:
- Calcium absorption in preterm low-birth-weight infants appears to occur via a nonsaturable pathway.
- The transcellular, vitamin D-regulated calcium absorption mechanism may not be fully developed in this population.
Abstract:
Net calcium absorption was evaluated in 103 low-birth-weight preterm infants by a 72-h balance technique. At birth the infants had a mean (+/- SE) gestational age of 30.9 +/- 0.2 wk and weighed 1.43 +/- 0.03 kg. When tested 3 wk later, their net calcium absorption averaged 58 +/- 1% with an intake of 80 +/- 2 mg Ca.kg body wt-1.d-1. Of the 103 infants, 58 had been fed low-birth-weight formulas supplemented with vitamin D. The remainder received banked human milk, of whom 34 were supplemented with vitamin D and calcium; 11 infants received no supplementation. Calcium absorption in the four subgroups did not differ significantly, with neither vitamin D supplementation nor supplementation with vitamin D and calcium affecting percent absorption significantly. Net calcium absorption was a linear function of intake (40-130 mg Ca.kg body wt-1.d-1) with a zero intercept. Because vitamin D supplementation did not increase net calcium absorption, it is concluded that in preterm low-birth-weight infants calcium absorption proceeds by a nonsaturable route, with the transcellular, vitamin D-regulated mechanism not yet expressed.