Significance Of Dietary Iron In Complementary Feeding

Iron is one of the important trace element found in human body that actively participates in various metabolic pathways, particularly erythropoiesis and neurodevelopmental processes.[1] Being an important micronutrient for neurodevelopment, dietary iron becomes an utmost vital nutritional component during infancy. Deficiency of dietary iron in early infancy/childhood results in depletion of iron stores in the body that could later result in modification of sensorimotor, cognitive/language, social/emotionaland psychological / behavioural activities in new-borns.[2]Therefore, maintaining iron stores in the body is essential for achieving optimal neural development of babies. ‘Complementary feeding’ serves as an important tool in maintaining and replenishing the iron stores in infants.

Depletion of Iron stores in the body

At birth

• Iron stores in neonates are specifically high (around 94 mg/kg fat-free mass) at time of birth due to the iron endowment at birth in the body. [4]
•  Even though the proportion of iron store may vary in each infant depending upon the maternal iron status and associated pregnancy complications, but the iron stores of neonates are sizeable enough to meet its nutritional need during the first six months of life. [5]
•  Scientific evidences suggest that about 80% of foetal iron stores which were developed during first trimester of pregnancy serves as basic stocks for formation of foetal haemoglobin (Hb) during intrauterine life and reserve iron stores during early infancy. [6, 7]
• Soon after the birth, the foetal Hb gets gradually replaced with adult type Hb in order to match the higher environmental oxygen concentrations and Hb oxygen saturation of extra-uterine life. [7]
• A polycythaemic reaction takes place in the neonatal period, which replaces the foetal Hb with adult Hb; imperative to this there is a decreased stimulation of erythropoietin production and significant reduction in rate of erythrocyte release. [7]
• These physiological reactions during neonatal period reduces the Hb levels in body (approximately 30 to 50%) at six to twelve weeks after birth in term infants and one to four weeks earlier in preterm infants. [7, 8]

In Infancy

• Studies report that as the iron stores of the body shrink during early infancy i.e. six-twelve months of life, the plasma ferritin concentration also falls rapidly during this phase. [5]
• This decline in concentration of plasma ferritin can be easily managed by providing exogenous iron i.e. iron from dietary sources/complementary feeding. [5]
• These scientific facts are suggestive that there is a remarkable reduction in the endowed iron stores of an infant during first year of life and diet becomes the vital source for iron thereafter. Hence, adequate supplementation of dietary iron is required to maintain the apt levels of iron in the body and to prevent iron deficiency in infants.

Iron Deficiency in Infants

Epidemiology

The iron stores present at the time of birth gets rapidly consumed during first few months of life that exposes new-borns to the risk of developing iron deficiency and anaemia during infancy. The risk of having iron deficiency is particularly higher in preterm infants. Scientific evidence suggests that full-term infants have sufficient hepatic iron reserves for growth and development and do not require supplementation during the first six months of life. However, the iron reserves of preterm infants being comparably less than full term infants, exposes them to greater risk of iron deficiency even during first six months of life. [7] Iron deficiency during infancy could negatively affect the neurodevelopment and haemoglobin status of the baby. The global prevalence of iron deficiency anaemia (IDA) ranges from 25 to nearly 100% among infants; while majority of countries report prevalence rate greater than 70%. [9] As suggested by data from the National Family Health Survey (NFHS) III in India, the prevalence of IDA is as high as 70% among children less than five years of age.[10] Whereas, the prevalence rate of IDA surges to 79% for children under three years of age, indicating vulnerability of IDA in this age group. [10] Severity of IDA among children from age six months to thirty-five months usually vary from mild, moderate, severe, any anaemia (figure-1). [10, 11]

Figure 1
Comparison of Anaemia prevalence among children of age six to thirty-five months (*Adapted from the National Family Health Survey (NFHS) III in India)

Health Outcomes

• Iron deficiency during infancy could adversely affect the morphology, neurochemistry, and bioenergetics of the infant's central nervous system.[12]
• Animal model studies have illustrated that iron deficiency during early phase of post-natal life can alter the morphology of hippocampus and striatum areas of brain; similar changes in brain are anticipated in humans too. [13]
• Iron is accountable for proper functioning of oligo dendrites (myelin producing cells), an animal study reported that iron deficiency can alter the deposition of myelin in white matter and functioning of interneuron pathways. [14]
• Several in vitro studies done to evaluate role of iron in development of infant suggests that dopamine and norepinephrine metabolism are negatively altered by iron deficiency.[15]
• Altered dopamine can result in motor dysfunctioning, disturbance in sleep cycles and activity, and deteriorated learning and memory abilities; whereas altered norepinephrine can affect cognitive functioning and behaviour of an infant.[16]
• Most of the neurodevelopmental changes during infancy are irreversible and can persist throughout the life.[12]
• Dietary iron also play an important role in maintaining the haemoglobin concentration in infants. Deficiency of iron during this phase may result in iron-deficiency anaemia and other related diseases. [9]

Requirement of Iron during infancy

Till 6 months of life, iron present in the human breast milk is well absorbed by infants and is sufficient for the formation of heme. However, with marked increase in the nutritional requirement, it is suggested that iron-enriched solid foods should complement breast milk from 7 to 12 months of age. Considering the fact that iron is an essential component required for proper neurodevelopment and physical activity in infants, the Indian Council of Medical Research (ICMR) has recommended dietary allowance (RDA) of iron in infants (Table-1).

Table 1: Iron requirement during infancy

Source: Adapted from NUTRIENT REQUIREMENTS AND RECOMMENDED DIETARY ALLOWANCES FOR INDIANS A Report of the Expert Group of the Indian Council of Medical Research, 2009

Complementary feeding and Iron Complementary feeding refers to supporting foods that are regularly fed to the infant, in addition to breast-milk, for providing sufficient nutrients. The World Health Organization and IYCF (Infant and Young Child Feeding Practices), 2013 Guidelines recommends that complementary feeding be initiated after 6 months of life.[17] Complementary foods include food products that are either home- made, or manufactured or locally prepared, suitable as a complement to breast milk As per IYCF 2013 guidelines, the complementary feeding must be [18]

• Timely - meaning that they are introduced when the need for energy and nutrients exceeds what can be provided through exclusive breastfeeding;
• Adequate -  meaning that they provide sufficient energy, protein and micronutrients to meet a growing child's nutritional needs;
• Safe - meaning that they are hygienically prepared and stored, and fed with clean hands using clean utensils and not bottles and teats.

Breast milk despite being low in iron content is sufficient to meet the iron requirement of the baby till first six months of life. After the initial six months of life, the iron stores in body of the infant starts depleting fast. Hence, it is recommended that iron enriched complementary food should be given to all the infants along with breast milk after six months of age. [17]
Dietary iron from animal sources (red meat, fish, animal liver, egg yolk) and plant sources (pulses, beans and cereals, green leafy vegetables, peanut butter, iron fortified cereals) can be easily included in daily meal plan of an infant as per choices and preference.

Table 2: Selected Food Sources of Iron (* NIN)

Source: Nutritive Value of Indian Foods, National Institute of Nutrition, ICMR, 2007

However, it was found that the bioavailability of iron i.e. amount of the ingested iron absorbed and utilized by the body is significantly higher in animal sources (up to 22%) as than in plant sources (1-6%) of iron. [17] Dietary iron from animal and plant sources is absorbed better in presence of fructose, and ascorbic acid; while egg yolk, milk, tea or coffee reduces its absorption. Therefore, a diversified diet with reasonable proportions of animal and plant food products along with food products rich in ascorbic acid (25-75mg) is recommended to meet the iron requirements of infants. [17] Complementary food served to an infant should be in sync with iron density recommended for that age group (Table-3). [17]

Table 3: Recommended Iron Density in Complementary food

Unfortunately, due to numerous dietary restriction and preferences it is often difficult to meet the recommended iron density in complementary food served to infants. Hence, food fortification, and supplementation of food with iron are considered as best strategies to meet the dietary iron demands in infancy. [17] Additionally including ascorbic acid (vitamin-C) rich foods like orange, guava, lemon, mango, papaya, melon, banana, passion fruit, peach, tomato, green pepper, green leaves, cabbage, broccoli, and cauliflower leaves in daily meals increases the amount of iron absorption in infants. [17]

Figure 3: Sample diet plan for an Infant

Table 4: Recommendations on Complementary feeding from IYCF 2013 guidelines

Source: Adapted from Guidelines for enhancing optimal infant and young child feedin practices, Ministry of health and family welfare, Government of India, 2013