Nigerian Journal of Paediatrics

Nutritional iron and childhood intellect

Niger J Paediatr 2019; 46 (1):1 – 4

ORIGINAL

Asindi AA

CC – BY Nutritional iron and childhood

intellect

DOI:http://dx.doi.org/10.4314/njp.v46i1.1

Accepted: May 15th 2019

Abstract : Iron deficiency is the

pus per se plays important roles in

most prevalent micronutrient mal-

the consolidation of information

Asindi AA (

)

nutrition globally. It is known to

from short-term memory to long-

Department of Paediatrics,

affect both children and adults

term memory, and in spatial mem-

University of Calabar, Nigeria

especially

pregnant

women

ory that enables navigation.

Email: asindi.asindi@yahoo.com

largely in the developing coun-

Low iron levels in pregnant

tries. Iron is not only important

women correlates with low ferritin

for haemoglobin synthesis but

levels in their foetus and newborns

also for normal brain develop-

whereby several studies have

ment. In the body, the ferrous

clearly demonstrated the effect of

formis converted into ferritin

iron on developmental milestone

which is the active molecule. The

regarding cognition and behaviour.

brain is especially sensitive to

Iron deficiency early in life, there-

variation in iron availability, in

fore, confers irreversible brain

part due to the high metabolic

dysfunction even after complete

demands of the brain that are sup-

brain iron repletion. Iron therapy

ported by iron. Iron is necessary

and replenishment of brain ferritin

for basic neuronal processes such

may revert to normal cognitive

as myelination, neurotransmitter

functions in adults and adolescents

production, and energy metabo-

but not in children. Rich sources of

lism. With neuroimaging support,

iron are meat, liver, dark leafy

Globus pallidus, caudate nucleus,

green vegetables, fish, poultry,

putamen, substantia nigra and the

peas and beans. Pregnant women

hippocampus have been of pri-

require routine daily iron supple-

mary interest in studies of iron

ment; lactating woman and all

because they show robust and

children should be fed balanced

quantifiable levels of iron content.

diet. Special iron supplement

Furthermore, these regions are

should be provided for preterm and

central to cognitive abilities that

small-for-gestational-age infants

develop across childhood and

from the age of two months.

adolescence, such as processing

speed, cognitive-motor control,

Keywords: Iron deficiency, child-

reward-processing, and working

hood, Intellectual impairment.

memory function. The hippocam-

Introduction

Dietary iron is converted to ferritin which is the active

form of iron in the body. Apart from haemoglobin syn-

Iron deficiency (sideropenia) is the most prevalent nutri-

thesis, ferritin is a necessary element in the development

ent deficiency in the world afflicting an estimated 2.5 – 5

and functioning of the nervous system. Infants and chil-

billion people.

1,2

It is more common in developing coun-

dren with low ferritin levels are at riskof impairment of

tries where 46 – 66 per cent of all children under 4 years

brain development and function.

3, 6-8

of age are anaemic.

3-5

More than 50 per cent of paediat-

ric anaemia in the developing countries can be attributed

Because iron is involved in the function of various en-

to iron-deficiency with a peak prevalence among those

zymes and neurotransmitters in the central nervous sys-

in the 6-24 months age bracket. Maternal sideropenic

tem hence low serum levels of ferritin is postulated to

lower seizure threshold, including febrile convulsions.

anaemia complicates 30 – 50 per cent of pregnancies in

developing countries; in contrast, in developed countries

Restless Legs Syndrome appears to be related to deficits

in brain iron content and metabolism. Other conditions

where iron supplements are routinely administered, this

figure is less than one percent. The most common cause

associated with deficeit in brain iron contents and me-

of foetal/neonatal iron sideropenia is maternal iron defi-

tabolism in children and adolescents include syn-

affective respiratory crises,

13,14

cope, stroke,

ciency. Infants born to mothers suffering from iron-

and

schizophrenia.

deficiency anaemia have lower iron levels and are more

prone to anaemia.

This review focuses on what impact iron deficiency

hason the intelligence of children.

ence or education by perceiving, discovering, or learn-

ing. It is synonymous with appreciation, cognition and

Neurobiology and neurophysiology of Iron

intelligence. It requires the storage of information

Human nutritional requirement for brain function in-

(memory) in the cerebral cortex and the retrieval (recall)

clude proteins, certain types of fat, iron, zinc, copper,

of same in appropriate circumstances. Children exposed

iodine, selenium, vitamin A, choline and folate. Iron is

to iron deficiency both in utero and in the newbornpe-

the most abundant transition metal within the brain, and

riod

will suffer irreversible mental deficiency. Iron-

is vital for a number of cellular processes including neu-

deficiency anaemia is common during the second and

rotransmitter synthesis, myelination of neurons and mi-

third years of life and has variably been associated with

tochondrial function. Theimpact of the deficiency of any

developmental and behavioural impairments, hence it

nutrient on brain development is determined by the pe-

can influence motor and cognitive skills and the children

so affected will present with the following:

3,7

riod in which the deficiency occurs, its degree and dura-

tion.

3,7

The specific influence of the deficiency of a

given nutrient depends on the physiological processes in

Depressed mood

individual parts of the brain in which the nutrient par-

Short attention span

ticipates, and is manifested as a neurological function

Loss of alertness

disorder in that specific area. The blood-brain barrier

Loss of interest in the surrounding

provides an effective regulatory point for iron movement

Poor memory

in the human nervous system. Ferritin moves from the

Poor school performance

plasma pool to the cerebral and spinal fluid, and from

the choroid plexus it moves into and out of the brain.

These brain related deficiets will limit the child’s capac-

Magnetic resonance imaging (MRI) has been used to

ity to learn hence impaired intellect in the short- and

map iron distribution in the brains of children and ado-

long-term. Subsequent therapeutic correction of the se-

lescent.

16,17

The highest concentrations are found in the

rum iron will not revert the brain function to normal. A

Globus pallidus, caudate nucleus, putamen and substan-

large number of children with attention deficeit hyperac-

tia nigra.

tivity disorder (ADHD) are known to be mentally re-

tarded. The hallmark of this condition is short attention

Ferritin is essential for a number of enzymes involved in

span and lack of focus which consequently affect learn-

3,6,7

neurotransmitter synthesis

including tryptophan hy-

ing.ADHD has been associated with an imbalance in the

droxylase

(serotonin)

and

tyrosine

hydroxylase

brain level of dopamine, a neurotransmitter which re-

(norepinephrine and dopamine). Iron is related to the

quires iron for its synthesis.

Serum or peripheral iron

activity of monoamine oxidase, an enzyme critical for

in ADHD children is known to be normal but study has

proper rates of degradation of these neurotransmitters. In

reported reduced brain iron in the thalamic region as

addition, iron is a cofactor for ribonucleotide reductase,

measured by magnetic resonance imaging (MRI) in

and is essential for the functioning of a number of elec-

ADHD patients suggesting a role iron in the pathogene-

sis of this disease.

20,21

tron transfer reactions related to both lipid metabolism

and brain-energy metabolism. Irondeficiency therefore

affects myelinisation, monoamine neurotransmitter syn-

A limited number of studies have been conducted to

thesis and hippocampus metabolism during infancy.

determine if iron deficiency during non-developmental

Reductions in speed (myelinisation), changes in motor

periods of life are associated with changes in behaviour,

control

and

affect

(monoamines),

and

memory

cognition and brain function.

Studies in adolescents

(hippocampus) all bear witness to these influ-

who were iron deficient, but not anaemic, revealed al-

ences.

2,3,6

The hippocampus is part of the limbic system

terations in cognitive functioning that could be attrib-

and plays important roles in the consolidation of infor-

uted to iron depletion but not anaemia. When specific

mation from short-term memory to long-term memory ,

tests of attention were performed, iron-deficient anaemic

and in spatial memory that enables navigation. Informa-

adolescents performed less well than iron-sufficient

teens but these individuals did respond to iron therapy.

17,

tion is initially processed and consolidated by the hippo-

campi before being stored in the cerebral cortex.

Impact of iron deficiency on childhood intelligence

Iron is important for normal development of the brain

which is the seat of human memory. Iron deficiency

Conclusion and recommendation

during pregnancy and lactation causes irreversible dam-

age to foetal/neonatal brain development and function,

Iron-deficiency anaemia (and low serum iron) in preg-

which may be manifested as arrested cognitive and so-

nancy and childhood in developing countries is largely

cial development.

2,7

The basal ganglia and hippocampus

related to under nutrition thus making this problem a

support a number of cognitive processes, including

high-priority topic and highlights the key role of primary

higher-order cognitive functions such as general intelli-

and secondary prevention. Studies have shown that iron-

gence.

18,19

deficiency anaemia in pregnancy creates a significant

risk of reducing foetal iron storage thus causing cerebral

dysfunction to occur in utero. Even if the iron defi-

3-5

Knowledge is a familiarity, awareness, or understanding

of someone or something, such as facts, information,

ciency is corrected after birth, their brain function may

descriptions, or skills, which is acquired through experi-

never be fully restored. Furthermore, the amount of iron

in the mother’s milk is not usually sufficient to satisfy

iron deficiency, a nutritional problem that can be pre-

vented, or treated.

24-26

the infant’s iron needs after the first six months of exclu-

Frequent pregnancy disorders

such as intrauterine growth restriction and gestational

sive breast feeding during the first year. Iron supple-

diabetes mellitus

5,28,29

ments for breastfeeding mothers has not produced satis-

increase the risk of iron defi-

factory results once the damage has already been done.

ciency in the late foetal and early neonatal period.

This highlights the importance of preventing iron defi-

ciency among women during pregnancy and breastfeed-

In view of all these, the routine programme of iron sup-

ing. It is also important to adopt some other preventive

plementation to every pregnant woman should be under-

measures to cover infants especially during the first two

taken with a greater level of seriousness especially in the

years of life when brain growth is most rapid. The brain

developing world countries. There is also the general

is formed from the third week of intrauterine of life; its

recommendation that iron should be administered to all

metabolism and volume continue to increase from birth

breastfed infants after the sixth month, and to all prema-

to adulthood;

at the age of five years a normal child

turely born infants and infants born with low birth

attains 90 per cent of his brain growth.

weight after the second month.

24,25

Additionally, serial capillary haemoglobin check-ups at

The WHO estimates that more than 30 per cent of preg-

well-baby clinics, is recommended. In areas where

nant women in developing countries has iron-deficiency

hookworm infestation is rife, heath education on envi-

anaemia and one in 4 to 5 babies develop iron deficiency

ronmental sanitation is mandatory plus regular deworm-

anaemia.

24,25

Anaemia is only a late manifestation of

ing programme partly towards preserving young brains.

iron deficiency, and iron deficiency without anaemia is

more widespread.

If subtle effects of iron deficiency in

infancy lay the ground for later problems in cognitive

Conflict of interest: None

and behavioural functioning, then a large unrecognised

Funding: None

population of children may be at risk due to perinatal

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