Maternal and Child Undernutrition 1
Maternal and child undernutrition: global and regional
exposures and health consequences
Robert E Black, Lindsay H Allen, Zulfiqar A Bhutta, Laura E Caulfield, Mercedes de Onis, Majid Ezzati, Colin Mathers, Juan Rivera, for the Maternal
and Child Undernutrition Study Group*
Maternal and child undernutrition is highly prevalent in low-income and middle-income countries, resulting in
substantial increases in mortality and overall disease burden. In this paper, we present new analyses to estimate the
effects of the risks related to measures of undernutrition, as well as to suboptimum breastfeeding practices on
mortality and disease. We estimated that stunting, severe wasting, and intrauterine growth restriction together were
responsible for 2·2 million deaths and 21% of disability-adjusted life-years (DALYs) for children younger than 5 years.
Deficiencies of vitamin A and zinc were estimated to be responsible for 0·6 million and 0·4 million deaths,
respectively, and a combined 9% of global childhood DALYs. Iron and iodine deficiencies resulted in few child deaths,
and combined were responsible for about 0·2% of global childhood DALYs. Iron deficiency as a risk factor for maternal
mortality added 115 000 deaths and 0·4% of global total DALYs. Suboptimum breastfeeding was estimated to be
responsible for 1·4 million child deaths and 44 million DALYs (10% of DALYs in children younger than 5 years). In an
analysis that accounted for co-exposure of these nutrition-related factors, they were together responsible for about 35%
of child deaths and 11% of the total global disease burden. The high mortality and disease burden resulting from
these nutrition-related factors make a compelling case for the urgent implementation of interventions to reduce their
occurrence or ameliorate their consequences.
Maternal and child undernutrition remain pervasive and
damaging conditions in low-income and middle-income
countries. A framework developed by UNICEF recognises
the basic and underlying causes of undernutrition,
including the environmental,
sociopolitical contextual factors, with poverty having a
central role (figure 1). Although addressing general
deprivation and inequity would result in substantial
reductions in undernutrition1 and should be a global
priority, major reductions in undernutrition can also be
made through programmatic health and nutrition
interventions. This paper is the first in a Series of five
papers that focus on the disease burden attributable to
undernutrition and the interventions affecting household
food availability and use, maternal and child care, and
control of infectious diseases. The first two papers
quantify the prevalence of maternal and child
undernutrition and consider the short-term consequences
in terms of deaths and disease burden, as measured by
disability-adjusted life-years (DALYs). They also discuss
the long-term educational and economic effects and
associations with adult chronic diseases, particularly as
countries go through the demographic, epidemiological,
and nutritional transitions.2–6 The third paper estimates
the potential benefits of implementing health and
nutrition interventions that current evidence indicates
are effective and applicable in low-income and
middle-income countries. The final two papers consider
the current state of such interventions and how they
could be implemented fully through actions at national
and global levels.
Undernutrition encompasses stunting, wasting, and
deficiencies of essential vitamins and minerals (col-
lectively referred to as micronutrients) as one form of the
condition known as malnutrition, with obesity or
over-consumption of specific nutrients as another form.
The term hunger, which literally describes a feeling of
discomfort from not eating, has also been used to describe
January 17, 2008
This is the first in a Series of five
papers about maternal and child
*Members listed at end of paper
Johns Hopkins Bloomberg
School of Public Health,
Baltimore, MD, USA
(Prof R E Black MD,
Prof L E Caulfield PhD); USDA,
ARS Western Human Nutrition
Research Center, Davis, CA, USA
(Prof L H Allen PhD);
Aga Khan University, Karachi,
Pakistan (Prof Z A Bhutta, MD);
World Health Organization,
(M de Onis MD, C Mathers PhD);
Harvard School of Public
Health, Boston, MA, USA
(M Ezzati PhD); and Mexico
National Institute of Public
Health, Cuernavaca, Mexico
(Prof J Rivera PhD)
Robert Black, Johns Hopkins
Bloomberg School of Public
Health, Baltimore, MD, USA
• Maternal and child undernutrition is the underlying cause
of 3·5 million deaths, 35% of the disease burden in
children younger than 5 years and 11% of total global
• The number of global deaths and DALYs in children less
than 5 years old attributed to stunting, severe wasting,
and intrauterine growth restriction constitutes the largest
percentage of any risk factor in this age group
• Vitamin A and zinc deficiencies have by far the largest
remaining disease burden among the micronutrients
• Iodine and iron deficiencies have small disease burdens,
partly because of intervention programmes, but sustained
effort is needed to further reduce their burden
• Suboptimum breastfeeding, especially non-exclusive
breastfeeding in the first 6 months of life, results in
1·4 million deaths and 10% of disease burden in children
younger than 5 years
• Maternal short stature and iron deficiency anaemia
increase the risk of death of the mother at delivery,
accounting for at least 20% of maternal mortality
undernutrition, especially in reference to food insecurity,
wherein people do not have “physical and economic
access to sufficient, safe, nutritious, and culturally
acceptable food to meet their dietary needs”.7,8
Undernutrition is an important determinant of maternal
and child health.9–12
The Millennium Development Goals (MDGs) state as
the first goal “to halve between 1990 and 2015 the proportion
of people who suffer from hunger.”7 One indicator to
monitor progress for this target is the proportion of
children who are underweight—ie, low weight compared
with that expected for a well-nourished child of that age
and sex. This anthropometric indicator can indicate
wasting (ie, low weight-for-height, indicating acute weight
loss), or much more commonly, stunting (ie, low
height-for-age, indicating chronic restriction of a child’s
potential growth). Those two conditions can have different
determinants and respond to different interventions.13
Therefore, consideration of wasting and stunting is more
useful than consideration of underweight. This series
primarily uses these two indicators, but also presents
information on underweight because weight-for-age has
been used in previous analyses.9–11 Reduction of fetal
growth restriction and micronutrient deficiencies is also
essential to achieving the MDGs and deserves high priority,
even though there are no MDG indicators for these
conditions. This Series also examines the consequences of
low body-mass index and short stature in women.
This paper consists mainly of new analyses of the
prevalence of nutritional conditions, risk factors, and
consequent disease burden; if this was not possible or
necessary, previously published results are presented.
The burden of disease attributable to maternal and child
undernutrition is presented for three world regions—
Africa, Asia, and Latin America—that include primarily
low-income and middle-income countries; only 1% of
deaths in children younger than 5 years occur outside
these regions. UN regions and subregions (webtable 1)
Prevalence and consequences
Maternal short stature and low body-mass index in
pregnancy and lactation
Maternal undernutrition, including chronic energy and
micronutrient deficiencies, is prevalent in many regions,
especially in south-central Asia, where in some countries
more than 10% of women aged 15–49 years are shorter
than 145 cm (webtable 2). Maternal undernutrition—ie,
body-mass index of less than 18·5 kg/m²—ranges
from 10% to 19% in most countries. A serious problem of
maternal undernutrition is evident in most countries in
sub-Saharan Africa, south-central and southeastern Asia,
and in Yemen, where more than 20% of women have a
body-mass index of less than 18·5 kg/m². With a
prevalence of low body-mass index around 40% in
women, the situation can be considered critical in India,
Bangladesh, and Eritrea. Maternal short stature and low
body-mass index have independent adverse effects on
The nutritional status of a woman before and during
pregnancy is important for a healthy pregnancy
outcome.14,15 Maternal short stature is a risk factor for
caesarean delivery, largely related to cephalopelvic
disproportion. A meta-analysis of epidemiological studies
found a 60% (95% CI 50–70) increased need for assisted
delivery among women in the lowest quartile of stature
(146 cm to 157 cm, depending on the region) compared
with women in the highest quartile.16 If operative delivery
to ensure a healthy birth is not available to women who
need it, both mother and baby are at risk.17 Even if
operative delivery is accessible, affordable, and safe,
anaesthesia and laparotomy increase the risk of maternal
morbidity.18 Low maternal body-mass index does not
seem to increase the risk of pregnancy complications and
assisted delivery.16 Rather, there seems to be a synergistic
positive effect of short stature and higher maternal
body-mass index on increasing these complications.19,20
Low maternal body-mass index is associated with
intrauterine growth restriction.11 Previous analyses
estimated the disease burden of low maternal body-mass
index as a risk factor for perinatal conditions,11 whereas
the estimates presented in this paper consider intrauterine
Adult size, intellectual ability,
metabolic and cardiovascular disease
Mortality, morbidity, disability
dwelling, assets, remittances,
pensions, transfers etc
Lack of capital: financial, human,
physical, social, and natural
and political context
environment and lack
of health services
Inadequate dietary intakeDisease
Maternal and child
Figure 1: Framework of the relations between poverty, food insecurity, and other underlying and immediate
causes to maternal and child undernutrition and its short-term and long-term consequences
See Online for webtable 1
See Online for webtable 2
growth restriction to be the risk factor for neonatal
conditions. Additional work is needed to quantify the
relative effects of low maternal body-mass index, extent
of weight gain in pregnancy, and maternal micronutrient
deficiencies on the occurrence and severity of intrauterine
Maternal undernutrition has little effect on the
volume or composition of breast milk unless
malnutrition is severe. The concentration of some
micronutrients (vitamin A, iodine, thiamin, riboflavin,
pyridoxine, and cobalamin) in breast milk is dependent
on maternal status and intake, so the risk of infant
depletion is increased by maternal deficiency.21 This
factor is most evident in the case of vitamin A, where
the content in breast milk is the main determinant of
infant status because stores are low at birth. Maternal
supplementation with these micronutrients increases
the amount secreted in breast milk, which can improve
Childhood underweight, stunting, and wasting
The prevalences of underweight, stunting, and wasting
worldwide and for UN regions are based on analysis
of 388 national surveys from 139 countries, applying
comparable methods, including use of the new WHO
Child Growth Standards.22–26 In 2005, 20% of children
younger than 5 years in low-income and middle-income
countries had a weight-for-age Z score of less than –2
(table 1). The prevalences were highest in south-central
Asia and eastern Africa where 33% and 28%, respectively,
For all developing countries, an estimated 32%
(178 million) of children younger than 5 years had a
height-for-age Z score of less than –2 in 2005 (table 1).22,23
Eastern and middle Africa have the highest prevalence
estimates in UN subregions with 50% and 42%,
respectively; the largest number of children affected by
stunting, 74 million, live in south-central Asia.
Of the 40 countries with a child stunting prevalence
of 40% or more, 23 are in Africa, 16 in Asia, and one in
Latin America; and of the 52 countries with prevalence of
less than 20%, 17 are in Latin America and the Caribbean,
16 in Asia, 11 in Europe, and four each in Africa and
<5 years in
stunted (95% CI)
Number stunted in
millions (95% CI)
wasted in millions
millions (95% CI)
Stunting=height-for-age less than –2 SD. Severe wasting=weight-for-length or weight-for-height less than –3 SD. Underweight=weight-for-age less than –2 SD.
Table 1: Childhood stunting, severe wasting, and underweight estimates and numbers affected in 2005 based on the WHO Child Growth Standards by
UN regions and subregions
Figure 2: Prevalence of stunting in children under 5 years
Oceania (figure 2). Including only countries with a
stunting prevalence of 20% or more, 36 countries account
for 90% of all stunted children worldwide (webtable 3).
These countries will be the focus of estimations of the
effects of interventions on disease burden.28 21 of these
countries are in Africa and, although fewer countries are
in Asia (13), they account for 61% of the total stunted
children because of their large populations. India, with
an estimated prevalence of 51%, has more than 61 million
stunted children, 34% of the global total; however, the
prevalence varies substantially by state within India
(figure 3). Within countries the prevalence of stunting is
generally highest for the poorest segments of the
population (panel 1, figure 4).29
The global estimate of wasting (weight-for-height
Z score of less than –2) is 10% (55 million children).
South-central Asia is estimated to have the highest
prevalence (16%) and numbers affected (29 million). The
same regional pattern is seen for severe wasting
(weight-for-height Z score of less than –3), often used as
a criterion for therapeutic feeding interventions, with a
prevalence of 3·5% or 19 million children (table 1). The
highest percentages of children with severe wasting are
seen in south-central Asia and middle Africa. Of the
36 countries with 90% of stunted children, the prevalence
of severe wasting varies from 0·1% to 12% (webtable 4).
For the disease burden estimations, it is important to
know the extent of overlap of the populations of children
younger than 5 years who are stunted (height-for-age
Z score <–2) and those who have severe wasting. To
examine this question, data from 19 Demographic and
Health Surveys were analysed.30 The surveys were done
between 1998 and 2005, and included two from south Asia,
ten from Africa, and seven from Latin America and the
Caribbean. The prevalence of severe wasting was higher at
younger ages and declined by 24 months. Conversely,
stunting prevalence increased progressively until reaching
a plateau around 24 months. In these countries, severe
wasting was not accompanied by stunting in 80–100% of
younger children and 40–50% of older children. Thus,
Axis break Error bar
Shaker 6·5 roma
Superscript1 2 3 4 5 6
Figure 3: Prevalence of stunting among children under 5 years old in India by
Panel 1: Disparities in stunting and dietary diversity
This Series of papers on maternal and child nutrition builds
on a framework that recognises the underlying causes of
undernutrition, including the environmental, economic, and
political contextual factors, in particular poverty. Figure 4A
shows the disparities in stunting prevalence between the top
and bottom wealth quintiles of the population, based on data
from Demographic and Health Surveys for 11 of the 36 focus
countries. In most countries the poor children have about
twice as much stunting as the wealthier children.
The three proximate determinants of child nutritional status
include food security, adequate care, and health. Each of
these is strongly affected by poverty. For example,
animal-source foods are an important component of child
diets, as a major source of protein and micronutrients; low
intake of these foods is a risk factor for stunting. Figure 4B
shows the gap between the proportions of children in the top
and bottom wealth quintiles who received these foods in the
24 h before the survey, in selected countries with available
data. Wide gaps are evident in most countries.
Like stunting, micronutrient deficiencies are also linked to
poverty. In India, for example, anaemia affects 79% of
children in the lowest wealth quintile, compared with the still
high prevalence of 64% in the top quintile.29
Figure 4: Stunting and dietary diversity
(A) Children aged 0–59 months who were stunted. Bars show the gap
between prevalence in the poorest (red) and least poor (blue) wealth
quintiles. (B) Children aged 12–23 months who ate meat, fish, poultry, or
eggs in the 24 h before the survey. Bars show the gap between intake in
the poorest (red) and least poor (blue) wealth quintiles.
See Online for webtable 4
See Online for webtable 3
identifying children who are stunted will not capture most
of those with severe wasting. Furthermore, stunting and
severe wasting are not necessarily associated on a
geographical or ecological basis—ie, countries with a
similar stunting prevalence can have a several-fold
difference in the prevalence of severe wasting.31
Eight data sets from low-income countries (Ghana,
Guinea Bissau, Senegal, the Philippines, Nepal, Pakistan,
India, and Bangladesh)32–38 were used for analysis of
disease risks associated with childhood undernutrition.
These data were from specific study populations, but
were broadly representative of these countries and
low-income countries in general. Children were grouped
by Z score as less than –3, –3 to less than –2, –2 to less
than –1, and –1 or more for each of these indices.
Generalised linear mixed models were used to estimate
the risk of all-cause mortality, as well as of death due to
diarrhoea, pneumonia, malaria, and measles for each of
the groups with Z scores less than –1. The estimated
odds ratios were then adjusted for confounding due to
socioeconomic factors that affect mortality through other
pathways, such as non-nutritional determinants of
infection or access to better clinical care. The adjustment
used data sets with robust measurement of socioeconomic
status from Nepal36,37 and Honduras39 and showed that
odds ratios were attenuated by 10% and 20%, respectively.
On the basis of these results, 15% attenuation was applied
to the odds ratios calculated with the generalised linear
mixed models for underweight, stunting, and wasting.
The odds ratios derived for cause-specific mortality were
also used for diarrhoea, pneumonia, and malaria
The risk of death increases with descending Z scores
for underweight, stunting, or wasting (table 2). The
increased risks are all significant for the below –3 category,
as are many in the other two categories.
–3 to <–2
–2 to <–1
Weight-for-age (Z score)
Height-for-age (Z score)
Weight-for-height (Z score)
*Ghana, Senegal, Guinea Bissau, the Philippines, India, Nepal, Bangladesh,
Pakistan. †Ghana, Senegal, and Guinea Bissau. ‡Nepal, Ghana, Senegal, Guinea
Bissau, and the Philippines.
Table 2: Odds ratio for mortality by weight-for-age, height-for-age and
weight-for-height by cause of death
(% <2500 g)45
(% 2000–2499 g)
(% 1500–1999 g)
IUGR-LBW=Intrauterine growth restriction-low birthweight.
Table 3: Prevalence of intrauterine growth restriction-low birthweight and its components by UN region in 2004
Babies born at term (ie, who have completed 37 weeks of
gestation), but of low birthweight (<2500 g) are likely to
have had intrauterine growth restriction; we will refer to
this group as intrauterine growth restriction-low
birthweight. Various steps are used to estimate the
prevalence of this condition,40 which in developing
countries is present in 10·8% of livebirths each year. The
proportions of infants born at term weighing 1500–1999 g
and those weighing 2000–2499 g were estimated with
data sets from five countries (Bhutta Z, unpublished).41–44
These proportions were applied to regional (table 3) and
national (webtable 5) data to estimate that, of babies born
at term globally, 9·55% weigh 2000–2499 g, and
1·26% weigh 1500–1999 g.45
Poor fetal growth is rarely a direct cause of death, but
rather can contribute indirectly to neonatal deaths,
particularly those due to birth asphyxia and infections
(sepsis, pneumonia, and diarrhoea), which together
account for about 60% of neonatal deaths. To quantify
the risk of neonatal death associated with intrauterine
growth restriction-low birthweight, data from five
community-sampled prospective birth cohorts were
analysed: two from Nepal,42,44 and one each from India,43
Pakistan (Bhutta Z, unpublished), and Brazil.41 Each
cohort provided data for gestational age, birthweight,
survivorship, and cause of death during the first 28 days
The risks of all-cause mortality and death due to birth
asphyxia and infections for newborn babies weighing
1500–1999 g, 2000–2499 g, and 2500 g or more (reference
group) were examined. Babies weighing less than 1500 g
were excluded from the analysis because they were likely
to have been born preterm. Birth asphyxia and infections
as causes of death were selected for analysis because of
strong biological associations with impaired fetal
growth.46–52 With weighted linear regression techniques
to estimate the relation between birthweight category
and the log mortality rate, the relative risks for all-cause
mortality (five studies) and for deaths due to birth
asphyxia (two studies) and infection (four studies) were
calculated. Infants born at term weighing 1500–1999 g
were 8·1 (95% CI 3·3–19·3) times more likely to die, and
those weighing 2000–2499 g were 2·8 (95% CI 1·8–4·4)
times more likely to die from all causes during the
neonatal period than were those weighing more than
2499 g at birth. Based on two studies from South Asia,
for deaths due to birth asphyxia, the relative risks were 5·4
(95% CI 1·8–16·8) for those weighing 1500–1999 g
and 2·3 (1·3–4·1) for those weighing 2000–2499 g at
birth. For infectious causes, the relative risks were 4·2
(1·5–11·7) for those weighing 1500–1999 g and 2·0
(1·2–3·4) for those weighing 2000–2499 g.
Vitamin A deficiency
Countries were classified (figure 5) as having vitamin A
deficiency on the basis of the most recent data for several
indicators (serum retinol, conjunctival impression cytology,
and xerophthalmia) with criteria previously described.53
Brazil and China have subnational areas of deficiency so
only populations from these areas were considered at risk.
For these calculations all children in a country (or portions
of the country for Brazil and China) classified as having
vitamin A deficiency were considered at risk—ie, analogous
to the baseline status of populations in which vitamin A
intervention trials have been done. This prevalence was
then reduced on the basis of the latest figures for coverage
available (2005) from UNICEF of children receiving two
doses of vitamin A supplements in the past year (considered
to be fully protected from deficiency) or one dose
(considered to be protected for half the year).
Blindness from corneal scarring that is directly due to
xerophthalmia has an estimated disease burden from
direct sequelae.54 The relative risks of cause-specific
mortality as a result of vitamin A deficiency were derived
from a meta-analysis55 of the nine randomised
placebo-controlled trials in children 6–59 months showing
risk reduction with supplementation—ie, by inverting the
reduced risk shown by intervention.55,56 This calculation
yields a relative risk of 1·47 (95% CI 1·25–1·75) for
diarrhoea mortality and 1·35 (0·96–1·89) for measles
mortality related to vitamin A deficiency in the
non-supplemented population as a whole. Additionally,
the findings from three trials43,57,58 of vitamin A
supplementation of newborn infants in Asia show
reductions in mortality in the first 6 months of life. The
results from these trials are applied in the first 6 months
of life to indicate a relative risk of 1·25 for all deaths due
to infection and two-thirds of deaths due to prematurity—
ie, excluding a third of early neonatal deaths from extreme
prematurity. There has been an elevated risk of morbidity
from diarrhoea in observational studies;59 however,
placebo-controlled trials have shown an effect only on
diarrhoea severity, not incidence.55,60 One trial reported an
Vitamin A deficient
Figure 5: Prevalence of vitamin A deficiency in children under 5 years
See Online for webtable 5
effect of vitamin A on malaria morbidity,61 but another did
not;62 thus, this effect is not included in our estimates. An
increased risk of maternal mortality due to vitamin A
deficiency was not included because results from trials in
Nepal63 and Bangladesh64 are inconsistent, leading to a
non-significant pooled estimate.
The International Zinc Nutrition Consultative Group has
proposed a method for assessment of the population’s
risk of zinc deficiency based on indirect indicators—ie,
the prevalence of stunting, one of the clinical
manifestations of zinc deficiency, and the adequacy of
absorbable zinc in the food supply at the country level.65,66
The population’s risk of zinc deficiency was estimated
for the 178 countries for which information is available
from the UN Food and Agriculture Organization. The
latest prevalence of stunting for 131 countries was
obtained from the WHO Global Database on Child
Growth and Malnutrition.24 Data from other sources were
used to classify 35 additional countries by stunting
prevalence. Each country was classified into three
categories of risk of zinc deficiency on the basis of the
combination of stunting prevalence and adequacy of zinc
in the food supply.65,66 Countries at high risk of zinc
deficiency are those with a stunting prevalence of more
than 20% and estimated prevalence of inadequate zinc
intake of more than 25%; countries at low risk of zinc
deficiency are those with stunting prevalence of less
than 10% and inadequate zinc intake of less than 15%;
countries at medium risk of zinc deficiency are those
with all other combinations of the categories of stunting
prevalence and adequacy of zinc in the food supply. All
the trials of zinc supplementation included in the disease
burden risk estimates were done in countries classified
as having medium-high zinc deficiency. The national
prevalence of zinc deficiency is high in south Asia, most
of sub-Saharan Africa, and parts of Central and South
America (figure 6). In countries classified as having zinc
deficiency, all children were considered to be at risk.
Zinc deficiency in children results in increased risk of
diarrhoea, pneumonia, and malaria, as evidenced by
many randomised placebo-controlled trials done in
various populations in all regions of the world.67–71 The
relative risk of deficiency for outcomes in the at-risk
populations can be calculated by inverting the reduction
in morbidity and mortality seen in the trials of zinc
supplementation. The pooled relative risk for morbidity
associated with zinc deficiency is 1·09 (95% CI 1·01–1·18)
for diarrhoea, 1·25 (1·09–1·43) for pneumonia, and 1·56
(1·29–1·89) for malaria.72,73 For mortality in infants aged
1–59 months the relative risk is estimated to be 1·27
(0·96–1·63) for diarrhoea, 1·18 (0·90–1·54) for
pneumonia, and 1·11 (0·94–1·30) for malaria, based on a
meta-analysis (S Sazawal, unpublished) of randomised
controlled trials in Bangladesh,74 Nepal,71 and Zanzibar.69
These values were used in the estimates of disease
burden for the age group 6–59 months because this age
group has a more consistent benefit in supplementation
trials than infants younger than 6 months.
Iron deficiency anaemia
According to a WHO review of nationally representative
surveys from 1993 to 2005, 42% of pregnant women and
47% of preschool children worldwide have anaemia.75 For
these analyses, 60% of this anaemia was assumed to be
due to iron deficiency in non-malaria areas and 50% in
The major cause of iron deficiency anaemia is low
consumption of meat, fish, or poultry, especially in poor
people (panel 1).77 In young children the peak prevalence
of iron deficiency anaemia occurs around 18 months of
age and then falls as iron requirements decline and iron
intake is increased through complementary foods.
Women of childbearing age are at high risk for negative
iron balance because of blood loss during menstruation
and the substantial iron demands of pregnancy.
Previous analyses examined the relation between
anaemia in pregnancy and risk of maternal mortality.12
An odds ratio of 0·8 (95% CI 0·70–0·91) for maternal
mortality was found for a 10 g/L increase in mean
haemoglobin in late pregnancy. These analyses also
assessed the effects of anaemia on child cognition: the
combined analysis of the five available trials found 1·73
(95% CI 1·04–2·41) lower IQ points per 10 g/L decrease
in haemoglobin.12 A separate meta-analysis of iron
supplementation trials an overall benefit of 1–2 IQ points,
in children receiving iron, but there was no effect in
children younger than 27 months.78
The prevalence of sequelae of iodine deficiency, such as
goitre, congenital hypothyroidism, and developmental
disability, have been estimated and assigned disability
weights to calculate disease burden.79 More recently the
prevalence of iodine deficiency has been measured by an
Figure 6: National risk of zinc deficiency in children under 5 years
indicator of low urinary iodine concentration; however,
the rates of resulting sequelae have not been linked to
this new exposure measure. Thus, previously used
methods have been retained for the analysis in this paper.
Iodine deficiency has adverse effects on both pregnancy
outcome and child development. Even mild, subclinical
maternal iodine deficiency during pregnancy impairs
motor and mental development of the fetus and increases
risk of miscarriage and fetal growth restriction. Maternal
supplementation with iodine in more severe deficiency
improves pregnancy outcomes especially if done by the
second trimester, and improves neurological and
cognitive development of the infant.80 There are
insufficient data on benefits to pregnancy outcomes from
interventions when deficiency is mild.81 Breast milk
iodine content is very low in areas of endemic iodine
deficiency, exacerbating depletion in infants and
increasing their risk of impaired development. A
meta-analysis showed that populations with chronic
deficiency have a 13·5 point reduction in IQ.82
Folic acid, vitamin B12, and other micronutrient
Other micronutrient deficiencies of concern in maternal
and child health include calcium, iodine, the B vitamins
(especially folic acid and vitamin B12), and vitamin D.
Calcium deficiency is recognised as the main cause of
rickets in Africa and some parts of tropical Asia, and
increasingly in other parts of the world.83 An
estimated 35–80% of children in countries such as Turkey,
India, Egypt, China, Libya, and Lebanon are vitamin D
deficient (serum 25[OH]D <15 ng/mL) owing to the
practice of shrouding, avoidance of skin exposure to
sunlight, and the fact that few foods are fortified with
vitamin D.84 Vitamin D deficiency in utero can cause poor
fetal growth and skeletal mineralisation and is followed by
lower concentrations of the vitamin in breast milk. Rickets
and poor bone mineralisation subsequently appear during
the first years of life. The fetus is relatively protected from
maternal calcium deficiency, but calcium deficiency
rickets can result from low intakes in young children.
Poor folate status at conception, especially in the
subgroup of women who are genetically susceptible,
increases risk of neural tube and other birth defects, and
possibly pre-eclampsia and other adverse outcomes.85 In
some but not all studies maternal vitamin B12 deficiency is
a risk factor for neural tube defects and early fetal loss.86 In
women with deficiency the content of B12 in breast milk
can be so low that symptoms of deficiency appear in their
breastfed infants, including failure-to-thrive, stunting,
poor neurocognitive function, and global developmental
delays, all of which can be irreversible. Adverse pregnancy
outcomes have been seen in association with thiamin,
riboflavin, and vitamin B6 deficiencies in the few published
studies, and a recently reported trial of a supplement
containing B vitamins along with vitamins C and E found
a reduction in births with intrauterine growth restriction.87
Risks associated with child feeding practices
The recommended feeding of children is exclusive
breastfeeding for the first 6 months of life and continued
breastfeeding through the second year of life. In Africa,
Asia, and Latin America and the Caribbean only 47–57%
of infants younger than 2 months are exclusively
breastfed, an estimate that is based on an analysis of
recent national survey data (figure 7 and webtable 6 for
36 countries). For children 2–5 months of age this
percentage falls to 25–31%. For children aged
6–11 months, 6% in Africa and 10% in Asia have stopped
breastfeeding, as have 32% in Latin America and the
The risk of morbidity and mortality from suboptimum
breastfeeding in young children has been documented in
observational studies.34,88 A random effects meta-analysis,
which included all identified papers with appropriate
data, was used to estimate the increased risk of
cause-specific morbidity and mortality in relation to four
patterns of breastfeeding in children younger than
6 months (exclusive—ie, nothing but breastmilk;
predominant—only water or teas in addition to
breast-milk; partial—other liquids or solids in addition to
breast-milk; and not breastfeeding), and two patterns
(breastfeeding or not) in children aged 6–23 months.34,88–93
Previous estimates did not separate predominant and
partial breastfeeding.94 In the first 6 months of life, the
relative risks were increased for each of the three patterns
that were compared with the reference pattern—ie,
exclusive breastfeeding, for diarrhoea and pneumonia
morbidity and mortality (table 4). The relative risks were
significant for predominant breastfeeding for all-cause
mortality and pneumonia incidence, and there were
similar, but not significant, point estimates for diarrhoea
and pneumonia mortality and diarrhoea incidence.
Compared with exclusive
breastfeeding had moderately higher relative risks than
Outcome 0–5 months6–23 months
Partial breastfeeding Not breastfeedingNot breastfeeding
1·79 (1·29–2·48)92 2·48 (0·23–27·15)92
Data are point estimate (95% CI), references.
Table 4: Relative risk of suboptimum breastfeeding (compared with exclusive breastfeeding from 0 to
5 months and any breastfeeding from 6 to 23 months)
See Online for webtable 6
predominant breastfeeding, and not breastfeeding had
very high relative risks. In infants aged 6–23 months
there was a statistically raised risk of not breastfeeding
for all-cause mortality and diarrhoea incidence, but there
was no significant raised risk for other outcomes.
Even with optimum breastfeeding children will become
stunted if they do not receive an adequate quantity and
quality of complementary foods after 6 months of age.
Most incident stunting (and wasting outside of famine
situations) happens in the first 2 years of life when children
have a high demand for nutrients and there are limitations
in the quality and quantity of their diets, especially after the
period of exclusive breastfeeding.95 This age group (younger
than 2 years) also has a high rate of infectious diseases
such as diarrhoea that adversely affect growth and
nutritional status. A study that quantified the relative
effects of poor complementary diet and infectious diseases
on reduced growth found that they were of roughly equal
importance in one setting in rural Bangladesh,96 but this
result might vary in other settings. Suboptimum
complementary feeding is clearly a determinant of
stunting, and improvements in most settings need to focus
on both feeding frequency and energy density, and ensure
an adequate quality diet,
micronutrients.97 There is a clear disparity in dietary quality,
as indicated by the lower consumption of animal source
foods by poor children (panel 1).
Information derived from efficacy trials that attempted
to improve complementary feeding through nutrition
education, food supplementation, or both, can provide a
perspective on the importance of suboptimum
complementary feeding as a determinant of stunting.
The effects on linear growth seem to be best with
interventions that use specific educational messages—
eg, on consumption of animal-source foods emphasise
energy density of the diet, and, in areas with food
insecurity or low consumption of sources of
food supplements with
Contribution of infectious diseases to stunting and
intrauterine growth restriction
Infectious diseases are important determinants of
stunting.100 Although there can be contributions to growth
faltering from respiratory illnesses101 or malaria,102 the
role of diarrhoea seems to be particularly important,103–106
perhaps because of its association with malabsorption of
nutrients, as well as anorexia and catabolism.107
To quantify the contribution of diarrhoea to the
occurrence of stunting, data sets from Bangladesh (1),104
Brazil (2),103,108 Guinea-Bissau (2),109–111 Ghana (1),112,113 and
Peru (3)105,114,115 were analysed. Data were pooled to estimate
the effects of diarrhoeal incidence on the odds of stunting
at 24 months of age. All were longitudinal studies that
enrolled children at or near birth and followed them with
regular anthropometric measurements and daily records
of diarrhoeal surveillance. Because children were
measured at different ages, the measurement of
height-for-age Z score at the oldest date in the interval
between 18 and 24 months of age was accepted as the
Z score at 24 months. Logistic regression was used to
model the stunting at 24 months as a function of diarrhoeal
incidence. Children were only included if they contributed
at least 250 days of follow-up, up to the date when the
outcome was measured. The effect of diarrhoeal incidence
on stunting did not differ by study (p=0·409; likelihood
ratio test), allowing us to pool across studies (webfigure).
By contrast, our analysis required study-specific intercepts
and study-specific gender effects. The odds of stunting
increased multiplicatively with each episode of diarrhoea.
The adjusted odds of stunting at 24 months of age
increased by a factor of 1·05 (odds ratio 1·05, 95% CI
1·03–1·07) with each episode of diarrhoea in the first
24 months. The magnitude of this effect was not affected
when the children who were stunted in the first 6 months
of life were excluded.
Malaria in pregnancy is associated with intrauterine
growth restriction which increases the risk of death in
infancy.116 Infection at the end of pregnancy seems to be
Global and regional disease burden from
The global burden of disease project
The global burden of disease project reports mortality
and burden of disease for 136 comprehensive categories
of specific diseases and injuries, and their sequelae.54 The
burden of disease measures the gap between the current
health of a population and an ideal situation where
everyone in the population lives into old age in full health,
in DALYs. DALYs combine years of life lost due to
premature death and years of life lived with disabilities
(YLD) into one indicator allowing assessment of the total
loss of health from different causes. One DALY can be
Key 1Key 1
Africa AsiaLatin America
and the Caribbean
<2 months 2–5 months
and the Caribbean
Figure 7: Percentage of children by breastfeeding pattern, age group, and region
See Online for webfigure
regarded as roughly 1 lost year of so-called healthy life.
Methods and data for estimating mortality and DALYs in
the global burden of disease project are described
WHO has made an incremental revision of the global
burden of disease for 2004, which included updating
mortality and causes of death, and revising YLD estimates
for selected causes if new data were available. Estimates
of child deaths by cause have been revised to take into
account new estimates of the total numbers of neonatal,
infant, and child deaths
country-specific estimates of deaths in children younger
than 5 years by cause based on models developed by the
WHO Child Epidemiology Reference Group,119,120 and
updated UNAIDS and WHO estimates for HIV/AIDS,
tuberculosis, and vaccine-preventable child deaths.121,122
YLD estimates for protein-energy malnutrition have been
updated to take into account latest WHO estimates of
stunting and wasting according to the new WHO
for 2004,118 updated
standards,23 and YLD estimates for iron deficiency
anaemia have been updated using the most recent data
from the WHO Global Database on Anaemia.123 All
estimates of death and disease burden attributable to
undernutrition in this analysis are for the year 2004.
The 136 diseases and injuries in the global burden of
disease project follow the rules of the international
classification of disease (ICD) system. The ICD considers
four groups of nutritional deficiencies, and their sequelae,
as possible direct causes of death: protein-energy
malnutrition, iron deficiency anaemia, vitamin A
deficiency, and iodine deficiency. For this reason,
estimates were made of the number of deaths and
amount of disability that could be directly attributed to
these conditions. As described above, in addition to these
direct deaths, undernourished children are at an
increased risk of illness and death from many infectious
diseases, also included in the global burden of disease
categories. Indeed, substantially more children die as a
result of the synergy between infectious diseases and
undernutrition than from the direct sequelae of the
nutritional conditions themselves.11 Like the ICD, global
burden of disease also includes low birthweight as a
direct cause of death; nearly all of these deaths in
developing countries are due to preterm births, not
intrauterine growth restriction among births at term.119
Estimating deaths and burden of disease attributable to
nutritional risk factors
To estimate the number of deaths from various infectious
diseases attributable to different forms of undernutrition,
the methods of the comparative risk assessment project
were used.124,125 In brief, for each risk factor and for each of
the diseases that are affected by it, population attributable
fractions were computed using the following equation,
which is for a risk factor with n levels of exposure.
Population attributable fractions estimate the proportional
reduction in mortality that would be seen if risk factor
exposure had been reduced to an alternative (counterfactual)
distribution that would result in the lowest population risk,
irrespective of whether currently attainable in practice.
This optimum exposure, referred to as the theoretical-
minimum-risk exposure distribution, results in estimates
of deaths and disease burden that could be avoided if all
levels of suboptimum nutrition were addressed, in a
consistent and comparable way across risk factors.
PAF=population attributable fractions. RRi=relative
risk of disease or mortality for the ith exposure category.
Pi=proportion of children/women of child-bearing age
in the ith exposure category. P´i=proportion of
children/women of child-bearing age in the ith exposure
Panel 2: Specific assumptions for calculating the population
attributable fraction for multiple nutritional risks
The hazardous effects of one risk are not mediated
through other risks
This assumption might not hold for zinc deficiency because
some of its hazardous effects are mediated through reducing
growth. On the basis of the effects of zinc supplementation on
linear growth,127 and the model used to estimate intervention
effects,28 it is estimated that around 46% of the excess risk for
zinc deficiency is mediated through stunting. There would be
no mediation via stunting for vitamin A deficiency128 or iron
deficiency,129 because of their lack of effects on growth.
The proportional risks for one risk do not depend on
exposure to other risks
This assumption seems to be valid in that there has been no
effect modification found in factorial design trials of
vitamin A, zinc supplementation, or both,130,131 and no
difference in effect of vitamin A supplementation by baseline
nutritional status by various anthropometric measures.37,132
Likewise, no significant differences have been seen with the
effects of zinc supplementation on infectious disease
morbidity in children with better or worse nutritional status.133
Exposures to these risks are uncorrelated
The data from the cohort studies used to estimate odds ratios
show that there was a small positive correlation between
severe wasting and stunting (the prevalences of severe
wasting in children with height-for-age Z scores below and
above –2 were 4·7% and 2·9%, respectively). There was also a
positive correlation between stunting and zinc deficiency, but
this is accounted for in the mediated effect mentioned above.
Correlation was not incorporated in the calculations, which
results in a slight underestimation of the combined effects,
but previous sensitivity analyses have shown that the
underestimation is small for these risks.126
PAF=∑Pi RRi–∑Pi RRi
scenarios. n=number of exposure categories.
Deaths and disease
protein-energy malnutrition (an ICD condition), and its
direct sequelae as estimated in global burden of disease,54
were added to the burden associated with underweight.
In estimating the disease burden for stunting and
wasting it is appropriate to add the direct protein-energy
malnutrition burden to only one; it was added to wasting
(or severe wasting) because this condition is most
consistent with mortality from severe acute malnutrition,
even though YLDs for chronic effects were attributed to
both stunting and wasting.
The nutritional status
stunting, and wasting—were treated as risk factors whose
exposures and relative risks applied to all children in the
age group 1–59 months, and intrauterine growth
restriction-low birthweight only for the first month of life.
The analyses for vitamin A and zinc deficiencies and
suboptimum breastfeeding, for which either exposure or
increased risk were age-dependent, had to be done for age
groups other than all children under 5 or neonatal, the
two groups that are readily available from global burden
of disease databases. The division of cause-specific deaths
between 4 weeks and 59 months by age (eg, for the interval
1–5 months, 6–11 months, 12–23 months) were from data
for total (all-cause) deaths by month of age estimated
using demographic techniques from complete birth
histories in demographic and health surveys.
Exposures and relative risks for the calculation of
infectious disease deaths
nutrition-related risk factors were largely newly derived,
as described in this paper; however, the estimation of the
direct sequelae was done using previous methods with
the results updated to 2004. A summary of the source of
the inputs is provided in webtable 7.
Cause-specific deaths can be caused by multiple risk
factors acting simultaneously, and hence can be prevented
by intervention on each of the risks. For example, some
deaths from diarrhoea could be prevented by removing
exposure to stunting, zinc deficiency, vitamin A deficiency,
or suboptimum breastfeeding. Such deaths are attributable
to all four risks when considered individually. As a result
of multi-causality, the population attributable fractions for
multiple risk factors that affect the same disease outcome
overlap and cannot be combined by simple addition;
rather their combined effect is generally less than the
crude sum of individual ones, because some deaths are
attributed to multiple exposures.126 Under specific
assumptions (panel 2), the combined (joint) population
attributable fraction that avoids double-counting can be
estimated from those of individual risks.126
in alternative/counterfactual exposure
burden associated with
and burden from
Deaths and burden of disease attributable to nutritional
Of the nutritional status measures for children,
underweight was responsible for the largest disease burden
(table 5). The burden due to severe wasting from infectious
diseases is modest compared with the other measures,
largely because most children with non-optimum weight
for height have a Z score of –1 to –3 and substantially fewer
have a score less than –3. The burden associated with all
levels of wasting was slightly less than that of stunting.
Stunting, severe wasting, and intrauterine growth
restriction-low birthweight together were responsible for
2·1 million deaths (21% of worldwide deaths in children
under 5) and 91·0 million DALYs (21% of global DALYs
for children under 5; 7% of global total DALYs). Of the
UN subregions, the disease burden attributed to these
anthropometric measures is highest in south-central
Asia (webtable 8), where India alone has 0·6 million
deaths and 24·6 million DALYs attributed to stunting,
severe wasting, and intrauterine growth restriction-low
birthweight. The undernutrition burden is also high in
eastern, middle and western Africa; these subregions,
which together have an under-5 population of 111 million
(93% of India), 1·1 million deaths, and 42·3 million
DALYs, showing higher relative and absolute effects
among African children.
Among the deficiencies of vitamins and minerals
examined, the largest disease burdens were attributed to
vitamin A and zinc deficiencies (table 6). Vitamin A
deficiency in newborn babies, infants, and children
resulted in about 6% of under-5 deaths, 5% of under-5
DALYs, and 1·7% of total DALYs. Zinc deficiency resulted
in about 4% of under-5 deaths and DALYs and 1% of total
Deaths Percentage of
deaths in children
under 5 years
DALYs in children
under 5 years
Intrauterine growth restriction-
Total of stunting, severe wasting,
and intrauterine growth
1 957 530
1 491 188
1 505 236
2 184 97321·4 90 96221·2
*Deaths (138 739) and DALYs (14 486 400) directly attributed to protein energy malnutrition included· †Included in
wasting. ‡Total takes into account the joint distribution of stunting and severe wasting.
Table 5: Global deaths and disease burden measured in disability-adjusted life-years (DALYs) in children
under 5 years of age attributed to nutritional status measures in 2004
Deaths Percentage of deaths in
children under 5 years
Percentage of DALYs in
children under 5 years
Vitamin A deficiency
Table 6: Global deaths and disability-adjusted life-years (DALYs) in children under 5 years of age
attributed to micronutrient deficiencies in 2004
See Online for webtable 7
See Online for webtable 8
DALYs. The regional patterns for disease burden
attributed to vitamin A and zinc deficiencies are similar.
The highest burden for each is in South-central Asia,
followed by several subregions of Africa (webtable 9).
Iron deficiency resulted in a relatively small number of
under-5 deaths and DALYs (table 6). This burden is directly
attributed to the sequelae of iron deficiency anaemia in
children including cognitive impairment.76 In addition,
iron deficiency anaemia in pregnancy is considered a risk
factor for maternal mortality; 115 000 deaths per year from
maternal causes, resulting in 3·4 million DALYs, have
been attributed to this risk factor.12 Iodine deficiency
results in a very small number of deaths, which is
attributed to an excess risk of death with congenital
hypothyroidism, and a modest number of DALYs that
primarily result from multiple sequelae from iodine
deficiency, including cognitive and motor impairment and
In an analysis taking into account the joint distribution
of nutritional status risk factors (intrauterine growth
restriction, stunting, severe wasting, and deficiencies of
vitamin A or zinc) and the fact that some of the effect of
zinc deficiency is mediated through stunting, it is
estimated that there were 2·8 million child deaths
(28% of under-5 deaths) and 114·0 million DALYs (27% of
under-5 DALYs) attributable to these forms of childhood
undernutrition. This constitutes 8·5% of the total global
There was a large disease burden attributed to
suboptimum breastfeeding, including 1·4 million deaths
(12% of under-5 deaths) and 43·5 million DALYs, which
is 10% of global under-5 DALYs and 3% of total DALYs.
Most of the attributable deaths (1·06 million) and DALYs
(37·0 million) were due to non-exclusive breastfeeding in
the first 6 months of life, accounting for 77% and 85%,
respectively, of deaths and DALYs attributed to
suboptimum breastfeeding. Again the highest disease
burden estimates are for south-central Asia and several
sub-regions of Africa (webtable 10). This risk factor was
combined with anthropometric status and deficiencies of
vitamin A and zinc in an analysis allowing for co-exposure
and avoiding double counting of disease burden. If one
assumes that the risks of suboptimum breastfeeding and
other nutritional factors are independent, the combined
mortality effects of all risk factors were 3·6 million child
deaths (35% of under-5 deaths) and 140·5 million DALYs
(35% of under-5 DALYs); this is 10% of the total global
disease burden. These estimates change only slightly if
the burden of disease directly attributed to iron and
iodine deficiencies are added. These results are robust to
assumptions about some of the effects of suboptimum
breastfeeding being mediated through other nutritional
exposures. For example, if 25% of the hazardous effects
of suboptimum breastfeeding are mediated through
other nutritional risks, the total number of attributable
child deaths is reduced to 3·5 million, still about
35% deaths and DALYs in this age group. Adding the
maternal deaths and DALYs due to iron deficiency
anaemia increases the total global disease burden
attributed to undernutrition to 11%.
The attribution of more than a third of child deaths and
more than 10% of total global disease burden to maternal
and child undernutrition demonstrates the importance of
these prevalent risk factors. The 21% of global deaths and
DALYs in children younger than 5 years old attributed to
stunting, severe wasting, and intrauterine growth
restriction-low birthweight, largely because of their
synergistic relationship with infectious diseases, constitutes
the largest percentage for any risk factor in this age
The estimated total burden attributed to the com-
bination of underweight and intrauterine growth
restriction-low birthweight is about the same—ie, 22% of
deaths, and disease burden in children younger than 5
years—as the burden attributed to stunting, severe
wasting, and intrauterine
birthweight. This result is lower than our previous
estimate that indicated that 35% of child deaths could be
attributed to childhood underweight and maternal low
body-mass index operating through intrauterine growth
restriction to affect low birthweight.11 There are several
reasons for this difference. The new estimates were done
for a different base year (2004 vs 2000) with modest
reductions in overall child mortality and in some major
causes of death, such as diarrhoea, malaria, and measles,
that are affected by the nutritional risk factors. Further,
there have been declining trends in the prevalence of
stunting in most regions.134 More importantly the current
estimates used the new WHO growth standards for all
nutritional status prevalence and mortality and morbidity
risk estimates. These factors, along with the use of
different data sets for much of the risk analysis, resulted
in somewhat lower relative risks of mortality than in
previous analyses,10,11 especially for children with Z scores
between –1 and –2. Thus, some of the difference in
estimated disease burden is due to changes in methods,
but it also is likely to indicate progress in preventing and
managing undernutrition and reducing some important
causes of death.
The methods used in these analyses indicate several
advances from those used previously.11,12,56,73 Most of the
risk relations were re-examined, as were the exposure
definitions and prevalences, with the most current
evidence. The latest information on total and cause-specific
child mortality was used. The new WHO growth standards
were used for all analyses. Importantly, the prevalence of
stunting is about 15% higher with the new standards than
with the previous growth reference.135 The attributable
deaths and DALYs were estimated for intrauterine growth
restriction, stunting, and severe wasting, separately and
together, as well as for all wasting and underweight.
Co-exposures were considered, and the resulting estimate
See Online for webtable 10
See Online for webtable 9
for the anthropometric and micronutrient factors, as well
as suboptimum breastfeeding, provides a total disease
burden without double counting that results from simple
addition of the burdens from individual factors.
These estimations using a risk factor method show that
449 000 child deaths can be attributed to severe wasting.
Estimates by others136 have ranged up to 1·7 million deaths
using a methodology based on actual mortality rates in
studies done an average 18 years (maximum 25 years)
ago, when overall child mortality rates were much higher
than today. The case fatality rates implied by these two
calculations would be 2% versus 9%. True case-fatality
rates for all cases of severe wasting identified in a
cross-sectional population survey are unknown, but are
almost certainly lower than these of severely malnourished
children presenting to hospitals or feeding centres in
emergency settings. Futhermore, over time case fatality
rates have decreased because of better treatment. Since
the prevalence of HIV infection has increased in some
populations, some of the deaths reported to have been
due to protein-energy malnutrition in civil registration
systems could actually have been due to AIDS, but the
magnitude of this possible misclassification is unknown.
Finally, direct application of case fatality (versus
proportional risk) overlooks the fact that some of the
exposed children would have non-zero risk of death
regardless of their severe wasting status. Irrespective of
whether the true number of deaths attributable to severe
wasting is closer to a half million or to 1·5 million a year,
therapeutic feeding interventions are important com-
ponents of nutrition programmes in settings where
severe wasting is common.
Deficiencies of vitamin A and zinc were confirmed to
be important risk factors in terms of their effects on total
child mortality. The current estimate of disease burden
due to vitamin A deficiency is similar to previous
estimates despite increases in the population coverage
with vitamin A supplementation, because of inclusion of
risk in the 0–5 month age group for the first time. In
other words, the true decline in the burden in children
above 6 months of age has been numerically compensated
by the finding that vitamin A is important in an even
younger age group. That the estimates of disease burden
due to zinc deficiency are about 40% lower than
previously reported73 is because of the lower relative risks
based on analysis of additional studies.72 The
WHO/UNICEF recommendation that zinc be used
along with oral rehydration therapy for all childhood
diarrhoea is just beginning to be implemented in many
countries, and preventive use of zinc supplementation
or fortification is uncommon. The high residual burden
of those micronutrient deficiencies indicates that
interventions need to be expanded, especially in
south-central Asia and Africa.
Iodine and iron deficiencies currently result in only
small disease burdens. For iodine deficiency, there has
been substantial success with promotion of the use of
iodised salt; this and other interventions should be
continued to prevent resurgence of the related disease
burden. For iron deficiency the disease burden in
children is relatively small, accounting for only 0·5% of
under-5 DALYs, despite inclusion in the calculations of
life-long developmental disability in 20% of children who
have ever had severe anaemia.76 This postulated
permanent disability has not been seen in all studies and
its existence might need to be reconsidered in the
future.137 Nevertheless, children with iron deficiency
anaemia should be treated to prevent any possible current
and future adverse effects. Iron deficiency anaemia is an
important contributor to maternal mortality, increasing
the risk of dying with blood loss during delivery.12
Suboptimum breastfeeding has large mortality
consequences worldwide, similar to those of stunting.
The estimate reported here is the same (1·4 million
deaths) as a previous estimate using a different
categorisation of breastfeeding practices (combining
partial and predominant breastfeeding) and different
mortality risks.94,138 The timing of initiation of
breastfeeding was not considered in these estimates.
There is epidemiological evidence to suggest that
beginning breastfeeding within the first day post partum
would have additional benefit with regard to mortality
even in exclusively breastfed infants, reaffirming
recommendations to begin breastfeeding immediately
after delivery.89 More than three quarters of the burden
attributed to suboptimum breastfeeding is due to
non-exclusive breastfeeding in the first 6 months of life
when even provision of water or teas leads to an increased
risk of death. These estimates do not consider the adverse
effect of transmission of HIV in breast milk. Recent
evidence indicates that conditions in which breast milk
substitutes are recommended for babies of HIV-positive
mothers are rarely met, and there is a net benefit of
breastfeeding in terms of HIV-free survival even in
populations with a high prevalence of HIV infection.139–141
Exclusive breastfeeding results in lower rates of HIV
transmission than partial breastfeeding with rates
of 1%142,143 and 4%140 being reported from studies in Africa.
With around 2 million babies born to HIV-positive
mothers every year,144 these transmission rates would
result in 20 000–80 000 HIV-infected infants in the first
6 months of life. Antiretroviral treatment for pregnant or
lactating women will substantially reduce these resulting
infections, and such treatment is increasing in Africa.144
Because HIV transmission continues with partial
breastfeeding after the first 6 months of life,145 early
breastfeeding cessation has been considered an option.
Evidence is still incomplete; however, a recent trial found
no difference in HIV-free survival at 24 months of age in
children who were randomly assigned to abrupt weaning
at 4 months of age or continued breastfeeding.146
Inadequate complementary feeding contributes to
stunting as do infectious diseases, especially repeated
episodes without adequate case management. These
exposures, which are arguably the key determinants of
stunting, were not modelled as risk factors in this paper.
However, the effects on stunting and related disease
burden of interventions to improve complementary
feeding and to reduce diarrhoea incidence are calculated
in a subsequent paper in the Series.28 Results presented
here on the effects of diarrhoea on the risk of stunting are
incorporated in these calculations of intervention effects,
but other infectious diseases and perhaps asymptomatic
infections are also likely to contribute to stunting.
The nutrition-related risk factors individually result in
large disease burdens, but often coexist both in individuals
and in populations. Stunting and severe wasting in
children 1–59 months of age are largely uncorrelated, and
the estimation of the joint effects of these two risk factors
resulted in a slightly smaller total disease burden than
simply adding their effects because even in the absence of
statistical correlation, some children would be exposed to
both conditions. Intrauterine growth restriction-low
birthweight was considered for these estimations to affect
only infants younger than 1 month, but in reality could
affect later ages. Vitamin A, zinc, iron, and iodine
deficiencies and the anthropometric measures as risk
factors are largely uncorrelated, but there is still overlap in
their risk because there is multicausality, such as diarrhoea
for vitamin A, zinc, and stunting. In addition to simple
multicausality, about half of the effect of zinc deficiency is
mediated through stunting; the rest is a more direct effect
on morbidity and mortality, probably as a result of reduced
immune function.147 The risk related to suboptimum
breastfeeding might in part be due to micronutrient
deficiencies resulting from inadequate dietary intake, but
is also due to avoidance of infection. Calculating the
combined effects of suboptimum breastfeeding and the
other nutrition-related risk factors found that, even after
accounting for overlapping effects from multicausality of
diarrhoea and pneumonia, about half of the disease
burden attributable to suboptimum breastfeeding was
added to the other risk factors. Therefore, even if all other
Panel 3: Research needs
• Development of methods to assess nutritional status and
• Prevalence of deficiencies of vitamin A, zinc, iron, and
iodine in subnational populations
• Consequences of nutritional deficiencies for mortality
from HIV/AIDS, malaria, and other important infectious
• Consequences of nutritional deficiencies for immune
competence, brain development, cognitive ability, and
other possible effects
• Overlap of micronutrients and their joint effects on
mortality and morbidity
• Development of international fetal and newborn growth
nutritional risks were addressed, a substantial number of
child deaths would still require interventions related to
Additional research will be important for improving
understanding of the distribution of nutritional de-
ficiencies in populations and their risk relations. Some
specific research topics are listed in panel 3. Despite the
remaining research needs, these results, which show
the high prevalence of various forms of maternal and
child undernutrition and their health consequences,
present a compelling justification for implementation
of effective nutrition-related interventions. The potential
effects of these interventions are considered in the third
paper in this Series, with particular attention to their
contribution to achievement of MDG 1 with reduced
undernutrition and also MDGs 4 and 5 regarding child
and maternal mortality.
RB conceptualised and coordinated the analyses and preparation of the
paper. Primary responsibility for specific topics were as follows: LHA,
maternal undernutrition and consequences of selected micronutrient
deficiencies; ZB, complementary feeding; LEC, analysis of intrauterine
growth restriction-low birthweight and childhood undernutrition risks
for mortality; MdO, stunting, wasting and low birthweight prevalence by
country and region; ME, analysis of risk factor attributable mortality and
disease burden; CM, update of country, regional, and global
disease-specific mortality and burden of disease for 2004; and JR,
exposure to zinc deficiency by country. All authors contributed to the
Analyses of national surveys for prevalence of underweight, stunting and
wasting based on new WHO Child Growth Standards: Monika Blössner,
Yang Hong, Allen Shoemaker (WHO, Switzerland). Provision of
estimates of prevalence of breastfeeding status: Ana Betrán, Jeremy Lauer,
(WHO, Switzerland). Review of relative risks of suboptimum
breastfeeding: Ai Koyanagi, Sunil Sazawal (Johns Hopkins Bloomberg
School of Public Health, USA). Provision of panel 1 (equity gaps in regard
to stunting and dietary diversity): Satoru Shimokawa (Cornell University,
USA), Cesar Victora (University of Pelotas, Brazil). Provision of data for
analysis of mortality risks related to anthropometric indicators:
Keith West, Luke Mullany, Parul Christian, Larry Moulton, James Tielsch
(Johns Hopkins Bloomberg School of Public Health, USA), Linda Adair
(University of North Carolina School of Public Health, USA), Kåre Mølbak
(Statens Serum Institut, Denmark), Zulfiqar A Bhutta (Aga Khan
University, Pakistan), A M Menezes (University of Pelotas, Brazil),
Michel Garenne (Institute Pasteur, France), Shams El Arifeen
(International Centre for Diarrhoeal Diseases Research, Bangladesh),
M Andersen (University of Copenhagen, Denmark). Provision of data for
analysis of socioeconomic confounding: Saul S Morris (London School of
Hygiene and Tropical Medicine, United Kingdom), Keith West (Johns
Hopkins Bloomberg School of Public Health, USA). Review of risk related
to maternal body-mass index: Anju Aggarwal (Johns Hopkins Bloomberg
School of Public Health, USA). Provision of data on vitamin A
supplementation coverage: Nita Dalmiya (UNICEF, USA). Assistance in
classifying countries as vitamin A deficient: Keith West (Johns Hopkins
Bloomberg School of Public Health, USA). Analysis of the contribution of
diarrhoea to stunting: William Checkley, Gillian Buckley (Johns Hopkins
Bloomberg School of Public Health, USA). Analyses of mortality and
burden of disease attributable to nutrition risk factors: Rodrigo Dias
(Harvard University Initiative for Global Health, USA). Analyses of age
patterns of deaths in children younger than 5 years: Kenneth Hill,
Thomas Laakso (Harvard University Initiative for Global Health, USA).
Analyses of contribution of undernutrition to mortality by cause at birth
and during childhood, confounding by socioeconomic factors and of
correlation between stunting and wasting: Ping Chen, Carmen Carrillo
(Johns Hopkins Bloomberg School of Public Health, USA).
Maternal and Child Undernutrition Study Group
Series steering committee—Robert E Black (Johns Hopkins Bloomberg
School of Public Health, USA), Zulfiqar A Bhutta (Aga Khan University,
Pakistan), Jennifer Bryce (Johns Hopkins Bloomberg School of Public
Health, USA), Saul S Morris (London School of Hygiene and Tropical
Medicine, UK), Cesar G Victora (Federal University of Pelotas, Brazil).
Other members—Linda Adair (University of North Carolina, USA),
Tahmeed Ahmad (ICDDR,B, Bangladesh), Lindsay H Allen (USDA ARS
Western Human Nutrition Research Center, USA), Laura E Caulfield
(Johns Hopkins Bloomberg School of Public Health), Bruce Cogill
(UNICEF, USA), Denise Coitinho (WHO, Switzerland), Simon Cousens
(London School of Hygiene and Tropical Medicine, UK), Ian Darnton-Hill
(UNICEF, USA), Mercedes de Onis (WHO, Switzerland); Kathryn Dewey
(University of California, Davis, USA), Majid Ezzati (Harvard School of
Public Health, USA), Caroline Fall (University of Southhampton, UK),
Elsa Giugliani (Federal University of Rio Grande de Sul, Brazil),
Batool A Haider (Aga Khan University, Pakistan), Pedro Hallal (Federal
University of Pelotas, Brazil), Betty Kirkwood (London School of Hygiene
and Tropical Medicine, UK), Reynaldo Martorell (Emory University,
Rollins School of Public Health, USA), Colin Mathers (WHO,
Switzerland), David Pelletier (Cornell University, USA),
Per Pinstrup-Andersen (Cornell University, USA), Linda Richter (Human
Sciences Research Council, South Africa), Juan A Rivera (Mexico National
Institute of Public Health), Harshpal Singh Sachdev (Sitaram Bhartia
Institute of Science and Research, India), Meera Shekar (World Bank,
USA), Ricardo Uauy (Institute of Nutrition, Chile).
Conflict of interest statement
We declare that we have no conflict of interest. As corresponding author,
R Black states that he had full access to all data and final responsibility to
submit for publication.
Funding for the preparation of the Series was provided by the Bill &
Melinda Gates Foundation. Meetings were hosted by the UNICEF
Innocenti Research Centre and the Rockefeller Foundation Bellagio
Conference Center. The sponsors had no role in the analysis and
interpretation of the evidence nor in writing the report and the decision
to submit for publication. We thank Barbara Ewing and Mary Rybczynski
for administrative assistance with the Series.
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