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Trace element excess in PKU diets?
E Sievers1, H D Oldigs, K Dörner
1Department of Paediatrics, University of Kiel, FRG.
Insights
Infants with phenylketonuria (PKU) fed specialized diets show higher copper and manganese retention. Current trace element supplementation in PKU formulas may need adjustment for early infancy.
Area of Science:
- Pediatric Nutrition
- Metabolic Disorders
- Trace Element Metabolism
Background:
- Limited data exists on trace element requirements for infants with phenylketonuria (PKU) on semisynthetic diets.
- Human milk trace element concentrations serve as a reference, but PKU formulas differ significantly.
Purpose of the Study:
- To assess the balance and retention of iron, copper, and manganese in early-diagnosed infants with PKU.
- To evaluate the suitability of current trace element supplementation in PKU formulas for the first four months of life.
Main Methods:
- Longitudinal balance studies (72h) were conducted on three infants with PKU at 2, 5, 8, 12, and 16 weeks of age.
- Dietary and fecal concentrations of iron, copper, and manganese were measured using atomic absorption spectroscopy.
Main Results:
- Median trace element concentrations in PKU diets (Fe: 4.8 mg/L, Cu: 1.7 mg/L, Mn: 0.43 mg/L) were higher than in human milk, primarily due to amino acid preparation supplementation.
- Significantly higher daily retention of copper (0.17 mg/kg) and manganese (6.4 µg/kg) was observed in infants fed the PKU diet.
- Median iron retention was 0.24 mg/kg.
Conclusions:
- The increased intake of trace elements from PKU formulas leads to higher retention rates in infants.
- Results raise concerns regarding the adequacy and appropriateness of current trace element supplementation levels in PKU formulas for infants under four months.
- Further research is needed to establish optimal trace element profiles for PKU management in early infancy.
Abstract:
Knowledge of trace element requirements of infants with phenylketonuria (PKU) fed a semisynthetic diet is limited. Three infants with PKU detected early were studied longitudinally in classical balance studies for 72 h, under domestic conditions, at the ages of 2, 5, 8, 12 and 16 weeks. Iron, copper and manganese concentrations in the diet and faeces were determined by atomic absorption spectroscopy. The median concentrations in the diet (4.8 mg Fe/L, 1.7 mg Cu/L, 0.43 mg Mn/L) exceed those in human milk. This is mainly due to supplementation of the amino acid preparation used. The increased intake led to a significantly higher daily retention of Cu and Mn from the PKU-diet fed, with a median of 0.17 mg Cu/kg and 6.4 micrograms Mn/kg body weight; the median retention of Fe was 0.24 mg Fe/kg. Our results confirmed the doubts about the suitability of the present trace element supplementation in formula for infants with PKU during the first four months of life.