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Summary o main points
1) Adequate nutrition during pregnancy
and the rst two years is necessary
or normal brain development, laying
the oundation or uture cognitive
and social ability, school success, and
productivity.
2) Undernutrition may inuence
brain development both directly and
indirectly. Nutrient deciencies directly aect
neurodevelopmental processes. Undernutrition aects childrens
experiences and behavior, which in
turn inuence brain development.
3) Priority should be given to the
prevention o severe acute malnutrition
(very low weight or height), chronic
malnutrition (as evidenced by
intrauterine growth retardation and
linear growth retardation or stunting),
iron-deciency anemia, and iodine
deciency. There is strong evidence
that they aect the developing
brain and compromise long-termcognitive, motor, and socio-emotional
development.
4) There is growing evidence that
breasteeding promotion, pre- and
post-natal multiple micronutrient
supplementation, pre- and post-natal
supplementation with essential atty
acids, and ortied ood supplements
provided during pregnancy and to the
child rom 6 to 24 months o age can
have benecial eects on early child
development. Few data exist on the
long-term eects o these interventions.
5) An integrated approach is likely to be
most eective or promoting optimal
child development, i.e., interventions
that combine improved nutrition with
other strategies such as enhancing the
home environment and the quality o
caregiver-child interaction.
Adequate nutrition or pregnant mothersand inants is necessary or normal braindevelopment. Pregnancy and inancy areimportant periods or the ormation o thebrain, laying the oundation or the devel-opment o cognitive, motor, and socio-emotional skills throughout childhoodand adulthood. Children with restricteddevelopment o these skills during early
lie are at risk or later neuropsychologi-cal problems, poor school achievement,early school drop out, low-skilled employ-ment, and poor care o their own children,thus contributing to the intergenerationaltransmission o poverty.
Many mothers and children in both low-and high-income countries are at riskor moderate undernutrition. Decreasedetal nutrition can be caused by poverty,maternal dieting, teenage pregnancy, anduterine vascular problems. Inadequate
Insight
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nutrition during inancy can result rompoor inant eeding practices and/or thelack o physical or economic access to nu-tritious oods to complement breasteed-ing. Many children worldwide ace theseconditions. For example, in 2010, 925 mil-lion people in the world experienced oodinsecurity,1 and birth rates among teenagegirls (age 15-19) ranged rom an average
o 103 per 1000 women in the lowest-income countries to 21 per 1000 women inhigher-income countries.2
An estimated 200 million children underage ve in low- and middle-income coun-tries are at risk o ailing to reach theirdevelopmental potential in cognitive, mo-tor, and socio-emotional abilities, partlydue to undernutrition3 (see Figure 1). Tistechnical brie reviews the evidence or theeect o undernutrition rom conceptionthrough the rst two years o lie on brain
Nutrition and brain
development in early lie
A&T Technica
Issue 4, January
Elizabeth Prado and Kathryn Dewey
Figure 1. Estimated percentage o children under 5 ailing to ulll their
developmental potential by country in 2004. Grantham-McGregor et al. (2007)
Missing or excluded
0-20%
20-40%
40-60%
60% and above
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Box 1. Brain development and the
childs experiences and environment
The brain develops its structural orm and
unctional capacity through dynamic bi-
directional inuences between biological
actors (such as nutrition), genetic actors,
the childs experiences, and the childs
own behavior.
Experience can aect brain development
in at least two ways. Certain
developmental processes have been
called experience-expectant because
the brain relies on them or normal
development.104 For example, the brainexpects visual input through the optic
nerve or the normal development o the
visual cortex.104
The absence o these expected
experiences impairs the
neurodevelopmental processes that
depend on them. These experience-
development and on both the short-termand long-term development o cogni-tive, motor, and socio-emotional skills.Appendix 1 denes these three domainso development and provides exampleso tests that are commonly used to assess
them in inants and older children.
Mechanisms or the efect o inadequate
nutrition on brain development
Undernutrition may inuence braindevelopment by directly aecting brainprocesses or indirectly by aecting chil-drens experiences and behavior. First,inadequate availability o nutrients duringgestation and inancy aects the structuraand unctional development o the brain.Gestation and inancy are periods orapid brain development. Te neural tubebegins to orm 16 days aer conceptionand within 7 months takes on a orm thatresembles the adult brain.4
Nutrients are required or many o thebiological processes that drive this trans-ormation. For example, they are neededor the creation o new neurons. A neuron
nsight
Early child growth
2
Figure 2. Structure o a neuron
expectant processes have been
distinguished rom experience-dependent processes.104 The latter
reers to the way the brain develops in
response to an individuals experiences
and acquired skills. For example, a
neuroimaging study demonstrated that
the rear hippocampus, a part o the brain
that underlies spatial memory, was larger
in London taxi drivers than age-matched
comparison subjects, presumably due to
their memory o the complex layout o
the London city streets.105
These experience-dependant processes
enable individuals to adapt to and thrivein their specic culture and environment.
Whereas experience-expectant processes
are more likely to occur early in lie,
experience-dependent processes continue
throughout lie, suggesting that neuronal
connections can re-organize in response to
experiences and that new neuronal growth
beyond inancy is possible.
The eects o undernutrition must be
understood in the context o thesemultiple biological and environmental
inuences as well as the interactions
between them. For example, low birth
weight inants born into amilies with
high socio-economic status are at lower
risk or poor developmental outcomes
than those born into disadvantaged
environments.19 Thus, protective
environmental actors can, in some
cases, buer the potential negative
eects o undernutrition. Conversely,
undernourished children rom
disadvantaged homes where protective
actors are lacking may show moreresponse to nutrition (and other orms o)
interventions.
Moreover, several studies have ound that
nutrition and psychosocial stimulation
together result in greater improvements
in child development than either
intervention alone.106
Neuron: one o the cells that constitutes nervous
tissue that is able to transmit and receive nervous
impulses, also called a nerve cell
Axon: a long projection o the neuron that
conducts nerve impulses away rom the nerve cell
body
Dendrite: a branching projection o the neuron
that conducts nerve impulses toward the nerve
cell body
Synapse: the place between nerve cells through
which nerve impulses pass rom one neuron to
another; this process is called neurotransmission
Neurotransmitter: a substance that transmits
nerve impulses across a synapse, or example,
acetylcholine and dopamine
Myelin: a sot white material o lipid and protein
that covers axons to insulate and accelerate
nerve impulses
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A&T Technica
Issue 4, January
is pictured in Figure 2. Nutrients are also
needed or the growth o axons and den-drites (also see Figure 2), the ormation osynapses, and the covering o axons withmyelin, which is atty matter that acceler-ates the speed o nerve impulses travelingrom one cell to another. Inadequate avail-ability o energy, protein, atty acids, andmicronutrients impairs these neurodevel-opmental processes.5 Tese nutrients arealso important or brain unction through-out childhood and adulthood, or example,or the maintenance o brain tissue andor neurotransmitter synthesis.6, 7 Most
o the evidence or these direct eectson the brain comes rom animal modelso nutrient deciency. A recent paperreported that moderate (30%) reductionin maternal ood intake during the rsthal o pregnancy in baboons negativelyaected etal brain development eventhough etal weight was not aected andmaternal weight was only slightly aected.Tis suggests that the brain can be aectedby moderate undernutrition during thisperiod even in the absence o overt signso undernutrition.8
Second, nutrition may aect braindevelopment indirectly through inu-encing childrens experiences. Childrensexperiences and environment are criticalactors in the development o the brainand the development o cognitive, motor,and socio-emotional abilities (see Box 1).
Undernutrition aects physical growth,
motor development, and physical activity,which in turn may inuence brain devel-opment through both caregiver behaviorand child interaction with the environ-ment9 (see Figure 3). Tat is, caregiversmay treat children who are small or theirage as younger than they actually are,which would result in less appropriatestimulation and thereore altered braindevelopment in an undernourished child.Undernourished children may also berequently ill and thereore ussy, irritable,and withdrawn. Tis could also lead care-
givers to treat them more negatively thanthey would treat a happy, healthy child.Additionally, lower activity levels wouldlimit the undernourished childs explora-tion o the environment and initiation ocaregiver interactions, which could alsolead to poor brain development. Someevidence suggests that these mechanismsmay contribute to delayed motor and cog-nitive development in inants and childrenwith protein-energy malnutrition10 andiron-deciency anemia.11, 12
An implication o the model presented inFigure 3 is that interventions targeting boththe child and the caregiver can operate atmultiple levels.13 For example, an inter-
vention that improves the childs nutrientintake may improve the childs physicalgrowth, activity levels, and behavior. Tiswould then enable the child to elicit and
receive age-appropriate care and positiveinteraction rom the caregiver and improvecognitive development. On the other hand,an intervention that improves the caregiv-ers sensitivity and appropriate response tochildrens cues, or example or hunger and
satiety, may improve the nutritional statuso the child. Tis would eed back into thechilds behavior and ability to elicit appro-priate interaction rom the caregiver. Tus,interventions aimed at either the child orthe caregiver may have cumulative andcascading eects over time.
Long-term consequences o
undernutrition in early lie
Severe acute malnutrition (low weight or
height) in early lie can have long-lastingconsequences on brain development evenaer nutritional rehabilitation. Many stud-ies have compared school-age childrenwho had suered rom an episode o severeacute malnutrition in the rst ew years olie to matched controls or siblings whohad not. Tese studies generally ound thatthose who had suered rom early mal-nutrition had poorer IQ levels, cognitiveunction, and school achievement, as wellas greater behavioral problems.14 o treatmalnourished children, WHO recom-
mends providing structured activities topromote cognitive development in additionto nutrition and health care. wo studiesin Uganda and Bangladesh have shownthat providing such stimulation can helpimprove mental and motor development inseverely malnourished inants.15
Chronic malnutrition, as measured bypoor physical growth, is also associ-ated with reduced cognitive and motordevelopment. From the rst year o liethrough school age, children who are
short or their age (stunted) or under-weight or their age perorm more poorlythan their normal-sized peers (on aver-age) in cognitive and motor tasks andin school achievement.16 Longitudinalstudies have also consistently shown thatchildren who had been stunted (heightor age < -2 SD below norm values) in
Figure 3. Potential mechanisms or the efect o nutrient deciency on childrens
cognitive, motor, and socio-emotional development
Adapted rom Levitsky & Barnes (1972) and Pollitt (1993)
Caregiver
behavior, parent-
child interaction
Brain
development and
unction
Nutritional
status
Cognitive, motor, and
socio-emotional
development
Level o child
interaction with the
environment
Physical
growth
Physical
activity
Illness
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the rst 2 years o lie continued to showdecits in cognition and school achieve-ment rom age 5 years to adolescence.16Tus, chronic undernutrition in early lieseems to have long-lasting consequencesor brain development.
Growth altering can begin beore birth,and the evidence indicates that being bornsmall or gestational age is associated withmild to moderately low perormance inschool during childhood and adolescence,and with lower psychological and intel-lectual perormance in young adulthood.17However, studies that have examined therelationship between low birth weight (
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