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The focus of recent global efforts to combat micronutrient
deficiencies has been on the three micronutrients iron, iodine and vitamin A
which are widely recognized to be critically important and frequently deficient.
A growing body of evidence now suggests that zinc might also be included in this
category. Zinc, a component of a large number of enzymes has protean and
essential functions in all biological systems, including immune function. Due to
the low zinc content of commonly consumed diets, poor bioavailability, and large
losses due to diarrhea, subclinical zinc deficiency is believed to be widely
prevalent among developing country children.
We report on a Symposium and Work- shop on "Zinc and Health in South Asia" in
Dhaka, Bangladesh (May 16-17, 1997) organized by ICDDR, B: Centre for Health and
Population Research and co-sponsored by UNICEF and the Sparkman Center of the
University of Alabama-Birmingham, USA. Scientists, planners, and policy makers
reviewed recent research on the relationship of zinc intake/supplementation to
child health and nutrition, defined the implications of the findings for
prograrns and policies, and developed recornmendations
for future research. .
Research findings from both published and as yet unpublished studies were
presented on the role of zinc in the treatment of acute and persistent diarrhea,
the prevention of diarrhea and pneumonia, the treatment of severe protein energy
malnutrition, and other outcomes.
Several studies (Bangladesh, India, Indonesia) produced convincing evidence that
zinc supplementation of children with acute diarrhea reduced diarrhea severity
and the evolution to prolonged diarrhea (i.e., lasting longer than 7
days).
Studies on the role of zinc to prevent childhood diarrhea and pneumonia
(Bangladesh, India) revealed benefit only in children who were malnourished or
older than 12 months. In view of findings from Latin America suggesting wider
benefit, the south Asian results perhaps indicate zinc has greatest benefit in
older and more malnourished children. A beneficial effect was observed. of
short-duration zinc as adjunctive therapy of undernourished and severely
malnourished children, although one study (Bangladesh) suggested a worse outcome
of severely malnourished children using a higher dose of zinc. Neither
long-duration (Bangladesh) nor short-duration (Pakistan) supplementation of
undernourished children had any effect on growth. One study (India) reported a
positive effect on the level of child's activity and, together with previous
reports from other regions, suggests a positive impact on childhood development
and cognitive function with zinc supplementation.
Safety issues of zinc supplementation were reviewed and the potential for ad-
verse effects of zinc on copper nutriture and immune function, especially in
malnourished children or with chronic use, was agreed to be an area where more
information is needed.
Program and Policy Implications of Studies on Zinc Supplementation
The Workshop on the second day considered evidence for the rationale as well as
risks and benefits of the promotion of a global intervention program with zinc.
There seems to be sufficient evidence of a benefit of zinc supplementation in
the treatment of acute watery diarrhea, but definitive information is lacking on
the scale of benefit of morbidity reduction and no evidence exists for mortality
reduction. However, the likely benefit of zinc on neural development and
cognitive functions was considered to be important. The group ultimately
recommended the following:
(i) Children with persistent diarrhea (duration
≥14
days) and all severely malnourished children (i.e. < - 3Z score weight
for age) should be treated with zinc during the course of illness; 20 mg
elemental zinc daily was felt to be appropriate.
(ii) Although children with acute diarrhea also benefit from zinc
supplementation, further studies related to effectiveness, cost, and practical
feasibility are needed before a general recommendation can be made.
(iii) At this point, it was concluded that large-scale intervention
programs in populations for disease prevention could not be recommended.
(iv) Zinc should not be promoted as a "magic cure" for acute watery diarrhea.
Although efforts to improve zinc intake may have a role in programs to manage
diarrheal disease, care must be taken to avoid promoting zinc supplements as a
new wonder drug. Ways to optimise zinc intake would need to be part of a
combined approach to diarrhea treatment and prevention that includes promotion
of oral rehydration solution, general nutritional therapy and advice
(breastfeeding, appropriate refeeding), and sanitation (hand washing, proper
disposal of excrement).
Research Priorities in Zinc and Health
The workshop review and discussion of research findings led to the
recommendation of the following research topics as higher priority:
(i) Effectiveness trials of zinc for the treatment of acute diarrhea;
(ii) Assessment of copper status and clinical deficiency within the
context of on going trials of chronic zinc supplementation or supplementation in
marginally nourished children;
(iii) Determination of the role of zinc in the therapy" of
life-threatening, dehydrating diarrhea, dysentery, pneumonia, and malaria.
(iv) Efficacy of chronic zinc supplementation to prevent pneumonia and
malaria, to enhance psychomotor and cognitive development, and to reduce
all-cause morbidity and mortality;
(v) Definition of optimal frequency and dose of zinc supplementation;
(vi) Investigations of zinc to reduce perinatal HIV transmission, to
treat and prevent HIV -associated diarrhea and pneumonia, and the effect on the
rate of HIV disease progression.
George J. Fuchs,
Interim Director, ICDDR,B,
Centre for Health and Population Research,
G.P.O. Box 128 Mohakhali,
Dhaka 1000, Bangladesh,
Dilip Mahalanabis,
Society for Applied Studies, Calcutta,
David Alnwick,
United Nations Childrens Fund, New York.
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