Dietary Diversity as a Measure of Nutritional Adequacy throughout Childhood. PhD Thesis

143 Pages·2006·0.65 MB·English

DIETARY DIVERSITY AS A MEASURE OF NUTRITIONAL ADEQUACY

THROUGHOUT CHILDHOOD

Melissa Christensen Daniels

A dissertation submitted to the faculty of the University of North Carolina at Chapel Hill in
partial fulfillment of the requirements for the degree of Doctor of Philosophy in the
Department of Nutrition.

Chapel Hill
2006

Approved by
Advisor: Linda S. Adair
Reader: Barry M. Popkin
Reader: Anna Maria Siega-Riz
Reader: Julie L. Daniels
Reader: Young K.N. Truong
ABSTRACT

Melissa Christensen Daniels: Dietary Diversity as a Measure of Nutritional Adequacy
throughout Childhood
(Under the direction of Linda S. Adair)

Malnutrition is a widespread concern in developing countries, impacting children’s
cognitive and physical development, quality of life and lifetime productivity. Interventions to
improve nutritional status in international contexts require identification of at-risk
populations and correct conclusions about general nutritional needs. Screening tools are
currently being developed to meet these needs.
Dietary diversity indicators are promising tools currently being studied. They are
typically counts of food groups in the diet (i.e. a sum of defined food groups consumed in a
defined time period) and are practical for field use because they are simply measured and
positively correlated with nutrient intakes.
We created age-specific diversity scores (based on a pre-existing tool) for use in both
early childhood and adolescence, and evaluated their relationship to nutritional adequacy,
nutritional status (measured by height for age Z-score), and their combined ability to predict
adult height. Data were taken from the Cebu Longitudinal Health and Nutrition Survey, a
Filipino birth cohort of 3,080 followed from the early 1980s through the present.
We found that using minimum portion requirements improved the relationship of scores
to nutrient adequacy for the 6 nutrients evaluated (vitamin A, iron, calcium, niacin,
riboflavin, iron). Modified scores also reflected amounts of food consumed, i.e. children
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with increasing dietary diversity also ate larger amounts of individual food groups. Related
increases in nutrient adequacy were largely due to these increased energy intakes, but there
were also small increases in the nutrient density of the diet at both ages. Linear models were
used to evaluate the relationship of both scores to height for age z-score. Scores at both ages
predicted crude increases in height for age z-score, although this relationship was weaker for
adolescents. After adjustment for confounders only the early childhood score was
significantly related height for age z-score, and only when mother’s had greater than 6 y of
education. In the crude longitudinal model, combined score increases did not predict ultimate
height improvements.
This research provides important insights about how diversity scores may be improved
for international malnutrition screening, and provides a basis for future research on the
performance of diversity scores across childhood.
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ACKNOWLEDGEMENTS

I wish to thank my committee for their expertise and thoughtful comments, which were
of great help in improving the content and direction of this project. I am also gratefully
indebted to the OPS staff for painstaking data collection over many years, and to Litlit Duazo
and Judith Borja for answering many questions about the data. Thanks also to Gina Kennedy
for help obtaining early copies of the dietary diversity protocol, as well as for assistance with
my related questions. I also offer special thanks to my advisor, Linda Adair, whose insights
and thought-provoking questions were indispensable in defining this project from the very
beginning. Thanks to my husband Scott for wonderful moral support as well as editorial
assistance. And thanks most of all to the Lord, without whom none of this would have
occurred.

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TABLE OF CONTENTS

Page
LIST OF TABLES....................................................................................................................x
LIST OF FIGURES.................................................................................................................xi
LIST OF ABRREVIATIONS.................................................................................................xii

Chapter
I. Introduction...........................................................................................................................1
A. Background.....................................................................................................................1
B. Research Aims................................................................................................................2
II. Literature Review..................................................................................................................4
A. Research is Needed to Combat Malnutrition...................................................................4
1. Malnutrition is a Key Concern in Developing Countries.............................................4
2. Appropriate Programmatic Strategies Depend on Meaningful Research Findings......5
3. Food Studies Fill Gaps Left by Micronutrient Studies.................................................5
4. Diet Quality Instruments are Appropriate for Use in Industrialized Countries............6
5. Dietary Variety Instruments are Well-Suited for Use in Developing Countries..........8
6. Dietary Variety Instruments are Associated with Nutrient Intakes..............................9
7. Dietary Variety Instruments are Associated with Growth..........................................10
8. Comparing Dietary Variety Instruments, Dietary Diversity
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Scores are most Versatile................................................................................................12

B. Research is Needed to Refine and Extend the Use of Dietary Diversity Measures.......13
1. Clarification is needed of the Relationship of Dietary Diversity
to Nutrient Density..........................................................................................................13

2. Tracking Analyses of Dietary Diversity.....................................................................15
3. Research is needed to Identify Determinants of Dietary Diversity............................16
4. Longitudinal Research is needed to Establish the Relationship
between Diversity and Anthropometry...........................................................................17

5. Potential Confounders of the Diversity and Growth Relationship
Need Careful Consideration............................................................................................18
C. Appropriateness of the data............................................................................................19
1. Data Quality................................................................................................................19
2. Population characteristics...........................................................................................20
D. Summary and Significance............................................................................................20
III. Methods............................................................................................................................21
A. Survey Design: The Cebu Longitudinal Health and Nutrition Survey.........................21
1. Study Design...............................................................................................................21
2. Exclusions...................................................................................................................21
B. Measurement of key variables......................................................................................22
1. Breastfeeding data.......................................................................................................22
2. Dietary data.................................................................................................................22
3. Other data....................................................................................................................22
IV. Dietary diversity scores can be improved through the use of portion
requirements: an analysis in young Filipino children..............................................................25

A. Introduction....................................................................................................................25
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B. Subjects and Methods....................................................................................................27
1. Subjects.......................................................................................................................27
2. Dietary data.................................................................................................................27
3. Creation of dietary diversity score..............................................................................29
4. Recommended nutrient intakes...................................................................................30
5. Probabilities of adequacy............................................................................................31
6. Nutrient densities........................................................................................................32
7. Sensitivity/Specificity Analysis..................................................................................32
8. Statistical analysis.......................................................................................................32
C. Results............................................................................................................................33
1. Sample characteristics.................................................................................................33
2. Relationship of diversity scores to dietary patterns....................................................34
D. Relationship of diversity scores to adequacy.................................................................36
1. Relationship with % recommended nutrient intakes...................................................36
2. Correlation with probability of adequacy...................................................................37
3. Linear increases in probabilities of adequacy.............................................................38
E. Sensitivity/Specificity Analysis.....................................................................................39
1. Roc Curves..................................................................................................................39
2. Selecting cutoffs and a preferred score.......................................................................40
F. Discussion.......................................................................................................................41
V. Dietary diversity among Filipino adolescents is related to dietary adequacy.....................56
A. Introduction....................................................................................................................56
B. Subjects and Methods....................................................................................................59
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1. Subjects.......................................................................................................................59
2. Dietary data.................................................................................................................60
3. Dietary Diversity Scores.............................................................................................62
4. Recommended nutrient intakes...................................................................................63
5. Probabilities of adequacy............................................................................................64
6. Selection of socioeconomic status variables...............................................................65
7. Statistical analysis.......................................................................................................65
C. Results............................................................................................................................66
1. Preliminary Analysis of Diversity Scores...................................................................66
2. Relationship between Diversity and Adequacy..........................................................69
D. Discussion......................................................................................................................73
E. Conclusions....................................................................................................................79
VI. Using 24 hour diversity at two time points is not sufficient to predict adult height.........86
A. Introduction....................................................................................................................86
B. Subjects and Methods....................................................................................................87
1. Sample.........................................................................................................................87
2. Anthopometric Data....................................................................................................88
3. Dietary Data................................................................................................................89
4. Socioeconomic Status Data.........................................................................................90
5. Analytical Methods.....................................................................................................91
C. Results............................................................................................................................92
1. Sample characteristics.................................................................................................92
2. Crude relationship between dietary diversity and HAZ.............................................93
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3. Factors explaining cross sectional relationships.........................................................94
4. Longitudinal analysis of adult height..........................................................................95
D. Discussion......................................................................................................................96
VII. Synthesis........................................................................................................................112
A. Overview of Findings..................................................................................................112
1. Dietary diversity scores can be improved through the use of portion requirements.112
2. Dietary diversity in Filipino adolescents is related to dietary adequacy...................113
3. Using 24 hour diversity at two time points is not sufficient to predict adult height.114

B. Public Health Significance...........................................................................................115
1. Our findings support minimum portion requirements as an
important improvement to dietary diversity scores......................................................115

2. Our findings provide important groundwork for dietary diversity-based
nutritional screening among adolescents......................................................................116

3. Our findings confirm the value of dietary diversity scores as a measure
of nutritional status in early childhood.........................................................................117

4. Our study is one of the earliest considering the impact of a persistent
pattern of dietary diversity on long-term nutritional status..........................................117

C. Strengths and Limitations............................................................................................118
D. Directions for Future Research....................................................................................121
REFERENCES......................................................................................................................125
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LIST OF TABLES

Table 1. Description of diet data and potential determinants of diet patterns and/or
development....................................................................................................................24

Table 2. Percent of children consuming ≥10 grams of each food group
by diversity score level at 24 months..............................................................................48

Table 3. Correlations of dietary diversity with probability of nutrient
adequacy and nutrient density.........................................................................................49

Table 4. Sensitivity and specificity analysis evaluating dietary diversity
scores for ability to detect high and low MPA...............................................................50

Table 5. Correlations between probability of nutrient adequacy and diversity
scores among Filipino Adolescents................................................................................80

Table 6. Linear regression of DDS (45g) on demographic and socioeconomic
factors of Filipino adolescents........................................................................................81

Table 7. Sample characteristics at baseline and age 15 years.............................................104

Table 8. Regressions of height for age z-score at 24 months on dietary diversity.............105

Table 9. Regression of height for age z-score at 15.5 years on dietary diversity...............106

Table 10. Adult height regressed on combinations of dietary diversity.............................107

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