Molybdenum supplementation in phenylketonuria diets: adequate in early infancy?
BACKGROUND
Molybdenum concentrations in formulas exceed those in human milk by far. Infants with phenylketonuria require semisynthetic phenylalanine-restricted diets. Because these diets are presently supplemented with molybdenum, a study was conducted to determine whether retention and plasma concentration in the recipients are equivalent to those of healthy breast-fed infants.


METHODS
Balance and plasma studies were conducted in healthy breast-fed infants (n = 17) and in patients with phenylketonuria (n = 4) at the age of 4 weeks, and the plasma investigations were repeated at the ages of 4 and 12 months. The samples were analyzed by atomic absorption spectroscopy (balance studies) and high-resolution inductively coupled plasma mass spectrometry (plasma).


RESULTS
Molybdenum intake and retention in all infants with phenylketonuria were more than 18 times those of breast-fed infants. The plasma concentrations reflected these differences. A median of 0.04 microg/l was assessed in breast-fed infants at 4 weeks and less than 0.02 microg/l at 4 months of age. Comparative results of infants with phenylketonuria were 2.9 microg/l and 2.5 microg/l, respectively. There were no significant differences between the groups at 12 months of age.


CONCLUSIONS
The phenylketonuria diets investigated showed excessive retention and plasma concentrations of the essential trace element molybdenum in early infancy. In view of these findings, the present practice of molybdenum fortification should be revised.
Sievers
E
E
Department of Pediatrics, University of Kiel, Germany.
Arpe
T
T
Schleyerbach
U
U
Schaub
J
J
D001903:Bottle Feeding; D001942:Breast Feeding; D019587:Dietary Supplements; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D007223:Infant; D007225:Infant Food; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D008297:Male; D008982:Molybdenum / Q000008:administration & dosage* / Q000378:metabolism; D010661:Phenylketonurias / Q000178:diet therapy* / Q000378:metabolism; D013057:Spectrum Analysis; D016482:Urinalysis
D008982:Molybdenum