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Calcium and phosphorus needs of premature infants
1Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada.
Insights
Determining calcium and phosphorus needs for low birth weight (LBW) infants is complex due to various factors. Separate recommendations for premature formulas and breast milk supplements may be necessary due to differing bioavailability.
Area of Science:
- Nutritional Science
- Pediatric Nutrition
- Neonatology
Background:
- Assessing calcium (Ca) and phosphorus (P) requirements for low birth weight (LBW) infants presents challenges due to confounding variables impacting mineral metabolism.
- Defining the clinical measure of Ca/P adequacy (e.g., serum normalization vs. intrauterine retention) significantly influences recommended intake levels.
Purpose of the Study:
- To reevaluate existing factorial approaches for estimating Ca and P requirements in LBW infants.
- To consider recent data on fetal mineral accretion and absorption efficiencies of various Ca and P sources.
Main Methods:
- Review and analysis of existing studies on Ca and P metabolism in LBW infants.
- Comparison of fetal accretion estimates (e.g., Ziegler et al. vs. Widdowson et al.).
- Evaluation of Ca and P bioavailability from different salt forms and milk combinations.
Main Results:
- Significant differences exist in Ca and P bioavailability depending on the source (salts and milk combinations).
- Updated estimates of fetal mineral accretion suggest a need to revise previous requirement calculations.
Conclusions:
- Current data suggest that recommended Ca and P intakes may need to be specific to the feeding source.
- Separate recommendations for premature formulas and preterm breast milk supplements are likely warranted due to bioavailability variations.
Abstract:
Interpretation of the available studies for the purpose of predicting the recommended Ca and P needs of LBW infants is difficult because of the number of confounding variables that can affect Ca and P metabolism. Clinically, the most important measure of Ca/P "adequacy" must also be determined. Clearly, the predicted recommended intakes for dietary Ca and P would be different if normalization of serum and urine Ca and P levels is chosen rather than achievement of intrauterine retention of mineral or bone mineral content as the index of adequacy of mineral intake. The factorial approach to the estimation of Ca/P requirements was previously proposed by Ziegler et al. A reevaluation of their estimation is warranted in the light of recent data on estimates of fetal accretion of minerals in the third trimester (2.9 used by Zeigler et al.) vs. 3.7 estimated by Widdowson et al. and reported efficiencies of absorption of various sources of Ca and P in feedings for LBW infants. Based on the observed differences in bioavailability of Ca and P from different salts and combined with various milks, it may be appropriate to recommend intakes of Ca and possibly P that are specific for premature formulas separate from that recommended for supplements to preterm mother's milk.