Nutrition News for Africa
Abstract - April 15, 2007
An article entitled “Zinc during and in convalescence
from diarrhea has no demonstrable effect on subsequent morbidity
and anthropometric status among infants <6 mo of age”
was published by Fischer Walker et al. in the American Journal
of Clinical Nutrition 2007;85:887-94
Introduction: In recent decades, the use
of Oral Rehydration Solution has led to a decrease in diarrhea
case fatality rates, but diarrhea incidence rates have remained
unchanged in the developing world. Zinc is recommended by
the World Health Organization and UNICEF as part of diarrhea
therapy for all children aged <5. When given for 10-14
days during and after a diarrhea episode, zinc has benefits
for the subsequent 2-3 months in decreasing the prevalence
of diarrhea and has been shown to help children maintain their
weight and to improve growth in the weeks after an episode.
The authors conducted a randomized, placebo-controlled trial
to assess the effect of zinc on diarrhea among infants 1-5
months of age in Pakistan, India and Ethiopia. The authors
previously reported that there was no effect of zinc on the
duration and severity of the treated diarrhea episode among
young infants. In this article, the authors report the effect
of zinc on morbidity and growth during 8 weeks of follow-up
after the index diarrhea episode. The current study is the
first to assess the effects of zinc on subsequent morbidity
and growth exclusively in infants <6 months of age.
Methods: A total of 1,110 infants aged 1-5
months with <72 hours of diarrhea and no signs of other
serious illness were enrolled in the study between October
2003 and February 2005 in Addis Ababa, Karachi, and New Delhi.
They were followed up weekly for a period of 8 weeks after
the initial diarrhea episode. Written parental permission
was obtained, and infants were randomly assigned to receive
10 mg zinc sulfate or placebo in the form of a dispersible
tablet once per day for 14 days. Infants were followed up
at home or in the clinic every 3 days by a trained data collector
until the infant passed <3 loose or watery stools/24 hours
and had maintained this state for >48 hours. On the last
diarrhea episode follow-up visit, as well as on the 4th and
8th weeks of follow-up, the infant’s length and weight
were recorded.
Results: Infants in the zinc group were
more likely to be girls and to have been exclusively breastfed
before the diarrhea episode than were infants who received
placebo. There were no significant differences between the
diarrhea incidence rates of infants in the zinc and placebo
groups after control for covariates. Infants in the zinc group
had more days of diarrhea during the follow-up period after
control for covariates. Weight and length were not significantly
different between the zinc and placebo groups at the start
of follow-up, week 4, and week 8.
Discussion: In this study, 14 days of zinc
for the treatment of diarrhea in young infants did not decrease
the incidence or prevalence of diarrhea episodes in the 8
weeks after treatment. These results differ from previous
ones showing a 34% decrease in the prevalence of diarrhea
in zinc-supplemented children. Also, there was no significant
difference in the incidence of respiratory infections or pneumonia
between the groups. No significant effect of zinc on growth
was observed during the 2 months after the diarrhea episode
and stunting rates increased from 27.8% to 31.7% in 8 weeks.
The authors advance that it is possible that the infants enrolled
in the current study did not respond to the zinc with the
benefits observed in other studies conducted in older children
because they had not yet become zinc deficient. Nearly all
the infants were receiving breast-milk, which contains highly
bioavailble zinc. A limitation of the current study was that
the authors did not assess zinc status via serum zinc concentrations
or the quantification of dietary zinc intake and as such they
could not assess the variation in effect, if any, by baseline
zinc status. Further investigation of the exact mechanisms
by which zinc helps maintain immune function and prevents
infectious diseases is needed to clarify why the positive
effect of zinc is observed in older infants, but not in all
infants under 6 months of age.
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