Long-term effects of iron and zinc supplementation during infancy on cognitive performance and growth 8 years later: a follow-up study Open Access

Pongcharoen, Tippawan (2010)

Permanent URL: https://etd.library.emory.edu/concern/etds/474299605?locale=en
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Abstract


ABSTRACT

Long-term effects of iron and zinc supplementation during infancy
on cognitive performance and growth 8 years later: a follow-up study
By
Tippawan Pongcharoen
Iron and zinc are important micronutrients for child cognitive development and
growth, particularly during infancy when brain development and physical growth are
rapid. Many studies have investigated the effects of iron and zinc interventions in
infancy, but the benefits of these interventions have been assessed only in terms of
outcomes in infancy. None of the intervention studies during the critical phase of infancy
have reported effects measured in school-aged children and beyond.
A randomized, placebo controlled trial of iron and zinc supplementation was
conducted in 4-6 month-old breastfed infants in Khon Kaen, Thailand from 1998-1999.
Infants were randomly divided into 4 groups receiving 1) 10 mg iron, 2) 10 mg zinc, 3)
10 mg iron+10 mg zinc, or 4) a placebo for 6 months. Improvements in iron and zinc
status and weight were found; no measures of cognitive development in infancy were
assessed in this study. These children were followed-up at 9 years of age in order to
assess long-term effects of iron and/or zinc supplementation on intellectual functioning
and physical growth (n=560). Results showed no differences in intelligence quotient (IQ),
Raven's CPM scores, or school performance among the 4 groups. There were no
differences in physical growth among these 4 groups. We also investigated the influence
of prenatal and postnatal growth on IQ and Raven's CPM scores at 9 years of age.
Results showed that early infancy growth that included a gain in weight, length, and head
circumference was correlated positively with measured IQ at 9 years of age. In addition,
solely a gain in length at late infancy was also positively correlated with measured IQ.
In summary, we found no long-term benefits of iron and/or zinc supplementation
during infancy on cognitive performance and growth at 9 years of age. However, we
found a significant relationship between early to late infancy growth and intellectual
functioning at 9 years of age. These findings suggest that nutrition intervention programs
should emphasize the importance of early childhood nutrition.

Table of Contents



TABLE OF CONTENTS

ACKNOWLEDGEMENTS………………………………………………………....
i
TABLE OF CONTENTS……...………………………………………………….....
ii
LIST OF TABLES……..……...………………………………………………….....
iv
LIST OF FIGURES...…..……...………………………………………………….....
v
CHAPTER 1: INTRODUCTION………………………………………..…….……
1
CHAPTER 2: LITERATURE REVIEW………………………………..…….….....
6
2.1 Overview of iron and zinc deficiencies…………………………..……….…
6
2.2 Roles of iron and zinc in cognitive development and growth during
childhood …………………………………………………………………....
9
2.3 Benefits of iron supplementation on cognitive development and growth
during childhood ………………………………………………………..…...
13
2.4 Benefits of zinc supplementation on cognitive development and growth
during childhood………………………………………………………...……
29
2.5 Iron and zinc interaction………………………………………………...…....
39
2.6 Effects of combined iron and zinc supplementation…………………..……..
41
2.7 Long-term effects of nutrition intervention during early childhood on
cogntive development and growth…………………………………………...
46
2.8 Thailand: country overview and description of intervention trial in infancy...
58
2.9 Window of vulneralility during infancy…………………………...…………
52
2.10 Influence of early growth on later cognitive development………..………….
52
2.11 Chapter summary…………………………………………………..………....
54
CHAPTER 3: METHODS………………………………………………..…………
56
3.1 Objectives and hypotheses…………………………………………..…………
56
3.2 Study design……………………………………………………………..…….
57
3.3 Study setting……………………………………………………………..…….
57
3.4 Study participants………………………………………………………..…….
58
3.5 Data collection…………………………………………………………..……..
59
3.6 Statistical analysis……………………………………………………………...
64
CHAPTER 4: LONG-TERM EFFECTS OF IRON AND ZINC
SUPPLEMENTATION DURING INFANCY ON COGNITIVE FUNCTION AT 9
YEARS OF AGE AMONG NORTHEAST THAI CHILDREN: A FOLLOW-UP
STUDY………………………………………………………………….…………... 74
Abstract……………………………………………………………………………
77
Introduction……………………………………………………………………….
78
Methods……………………………………………………………………..…….
80
Results……………………………………………………………...……………..
86
Discussion.………………………………………………………..….……………
89
Literature cited…………………………………………………………………….
94

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