Evaluation of dietary diversity scores to assess nutrient adequacy

152 Pages·2015·4.33 MB·English

E Evaluation of dietary diversity scores INVITATION
v
a
l
u
a to assess nutrient adequacy
ti You are cordially invited to attend
o
n the ceremony of my PhD thesis
o among rural Kenyan women
f defence entitled
d
i
e
t
a Evaluation of dietary diversity
r
y
d scores to assess nutrient
i
v
e adequacy among rural
r
s
i Kenyan women
t
y
s
c
o On Wednesday, 9 September 2015
r
e
s at 11:00 a.m.
t
o at the Aula of
a
s Wageningen University
s
e
s Generaal Foulkes 1a, Wageningen
s
n
u
t The ceremony will be followed by a
r
i
e reception in the Aula
n
t
a
d
e
q
u
a
c
y
a
m
o
n
g
r
u
r
a
l
K
e
n
y
a
n
w
o
m
e Sophie Ngala
n
S sophiengala @yahoo.com
.A Paranymphs
. N

g
a Dr. Fränzel van Duijnhoven
l
a
2 Franzel.duijnh [email protected]
0
1 S.A. Ngala Malgorzata Krolicka
5
[email protected]

Evaluation of dietary diversity scores to assess nutrient
adequacy among rural Kenyan women

S. A. Ngala

1
Thesis committee
Promotor
Prof. Dr F. J. Kok
Professor of Nutrition and Health, Division of Human Nutrition
Wageningen University
Co-promotors
Dr I. D. Brouwer
Associate Professor, Division of Human Nutrition
Wageningen University

Dr Alice M. Mwangi
Senior Lecturer, Department of Food Science, Nutrition and Technology.
University of Nairobi, Kenya
Other members

Prof. Dr E. G. Schouten, Wageningen University
Dr G. L. Kennedy, Bioversity International, Italy
Prof. Dr H. A. I. Bras, Wageningen University
Dr A. Geelen, Wageningen University

This resea rch was conducted under the auspices of the Graduate School VLAG
(Advanced studies in Food Technology, Agrobiotechnology, Nutrition and Health
S ciences)

2
Evaluation of dietary diversity scores to assess nutrient
adequacy among rural Kenyan women

S. A. Ngala

Thesis
submitted in fulfilment of the requirements for the degree of doctor
at Wageningen University
by the authority of the Rector Magnificus
Prof. Dr A. P.J. Mol,
in the presence of the
Thesis Committee appointed by the Academic Board
to be defended in public
on Wednesday 9 September 2015
at 11:00 a.m. in the Aula.
3
Sophia A. Ngala
Evaluation of dietary diversity scores to assess nutrient adequacy among rural Kenyan
women
149 pages.
PhD thesis, Wageningen University, Wageningen, NL (2015)
With references, with summaries in English

ISBN 978-94-6257-423-6

4
Dedicated to daughter Sally, Mum Teresa, Late Dad Ngala, Sella, Lucy, Jane, Magdalene,
Christopher and Angela

5
6
Abstract
Background
: The major cause of micronutrient deficiencies is low intake due to
monotonous diets, especially among women of childbearing age. The dietary diversity
score has been proposed and validated as a good proxy indicator for micronutrient
adequacy. However, there are still outstanding methodological questions related to
seasonal effects, food intake methods, selection of foods and the cut-off for estimating
the prevalence of acceptable nutrient adequacy. This thesis evaluated the
performance of a simple dietary diversity score for assessing nutrient adequacy in the
dMieettsh oofd rsural women in Kenya.
: The study was conducted in Mbooni Division, Makueni District, Kenya
among non-pregnant, non-lactating women of reproductive age having a child
between 2-5 years. Food consumption data was collected by 3 non-consecutive
quantitative 24hr-recalls and a qualitative free-listing 24hr-recall, in pre-harvest
(Period 1, October 2007, n=73) and post-harvest (Period 2, April 2008, n=203)
seasons. Dietary diversity scores (DDS) were derived based on 10 and 13 food groups
with a minimum intake threshold per food group of 0 and 15 g, respectively. Mean
pRreosbualbtsil:ity of adequacy (MPA) was calculated based on intake of 11 micronutrients.
The dietary diversity score (DDS) and mean probability of adequacy (MPA)
were significantly but moderately associated in both seasons (r=0.40 and r=0.38 in
Period 1 and 2), and the association was independent of season (p=0.45). The DDS
from a qualitative 24hr-recall (DDSql) showed little agreement with the quantitative
24hr-recall (DDSqn) with a mean difference (DDSqn-DDSql) of -0.51±1.46 (Period 1)
and -0.58±1.43 (Period 2), with lower correlations between MPA and DDS for DDSql
(r=0.14 and 0.19 in Period 1 and 2, p>0.05) compared to DDSqn (0.40 and 0.54 in
Period 1 and 2, p<0.01). The informative food-based scores and the food group-based
scores were moderately associated with mean probability of adequacy (r=0.54-0.59 in
Period 1; r=0.37-0.45 in Period 2) with higher values for informative food-based
scores. The Minimum Dietary Diversity score for Women and mean probability of
adequacy were significantly but moderately associated in both seasons (r=0.43-0.58 in
Period 1; r=0.24-0.50 in Period 2), but the use of the cutoff of consuming 5 or more
food groups as indication of nutrient adequacy resulted in high total misclassifications
in both periods.
7
Conclusion:
A dietary diversity score can be used as a simple proxy indicator for
micronutrient adequacy, independent of season. The dietary diversity score derived
from a qualitative free-listing 24hr-recall formed a poor indicator, needing further
refinement to improve its performance. The informative food-based score performs
moderately better in predicting nutrient adequacy, but its advantages do not outway
those of the food group-based scores, and the latter is therefore preferred. The
Minimum Dietary Diversity score for Women, formed a good indicator to predict

nutrient adequacy, but using the cutoff of 5 or more food groups resulted in an

overestimation of prevalence of adequate intake in our resource poor population.

8