Background: Molybdenum concentrations in formulas exceed those in human mil
k by far. Infants with phenylketonuria require semisynthetic phenylalanine-
restricted diets. Because these diets ate presently supplemented with molyb
denum, a study was conducted to determine whether retention and plasma conc
entration in the recipients are equivalent to those of healthy boast-fed in
fants.
Methods: Balance and plasma studies were conducted in healthy breast-fed in
fants (n = 17) and in patients with phe nylketonuria (n = 4) at the age of
4 weeks, and the plasma investigations were repeated at the ages of 4 and 1
2 months. The samples were analyzed by atomic absorption spectroscopy (bala
nce studies) and high-resolution inductively coupled plasma mass spectromet
ry (plasma).
Results: Molybdenum intake and retention in all infants with phenylketonuri
a were more than 18 times those of breast-fed infants. The plasma concentra
tions reflected these differences. A median of 0.04 (mu g/l was assessed in
breast-fed infants at 4 weeks and less than 0.02 mu g/l at 4 months of age
. Comparative results of infants with phenylketonuria were 2.9 mu g/l and 2
.5 mu g/l, respectively. There were no significant differences between the
groups at 12 months of age.
Conclusions: The phenylketonuria diets investigated showed excessive retent
ion and plasma concentrations of the essential trace element molybdenum in
early infancy. In view of these findings, the present practice of molybdenu
m fortification should be revised.