Background: Zinc is important for metabolism, cell growth, immunity, and de
fense against oxygen radicals. Extremely low-birth-weight (< 1000 g) infant
s have higher nutritional needs, but information on zinc is scarce. The aut
hors performed nutritional balances in 10 infants with birth weights of 500
to 999 g and who were fed with fortified human milk.
Methods: The authors collected infant feces, urine, and blood and human mil
k samples during 72 hours at 7 and 12 weeks of age. Zinc concentration was
measured by inductively coupled plasma-mass spectrophotometry, atomic emiss
ion spectrophotometry, and instrumental neutron activation analysis.
Results: Mean (SD) intake via human milk was 379 (+/- 373) mug (.) kg(-1 .)
d(-1) during both balances. Urinary excretion was high at 7 weeks of age,
decreased to half at 12 week, and was negatively correlated (P < 0.01) with
weight gain. Mean absorption was slightly positive at 7 weeks of age but z
ero or negative in most infants at 12 weeks of age. Retention was negative
in all infants at both observation periods, except in one infant during the
second balance. Clinical zinc deficiency developed in one infant at 12 wee
ks of age.
Conclusions: Zinc balances in extremely low-birth-weight infants are highly
variable and usually negative. Controlled trials are needed to assess need
for and benefits and risks of zinc supplemtation. (C) 2001 Lippincott Will
iams & Wilkins, Inc.