The nourishment children require, per unit body size, is greatest in infancy (Table 12.1), because of their rapid growth during this period. At 4 months of age, 30% of an infant’s energy intake is used for growth, but by 1 year of age, this falls to 5%, and by 3 years to 2%. The risk of growth failure from restricted energy intake is therefore greater in the first 6 months of life than in later childhood. Even small but recurrent deficits in early childhood will lead to a cumulative deficit in weight and height.

Table 12.1

Reference values for energy and protein requirements

Age	Energy (kcal/kg per 24 h)	Protein (g/kg per 24 h)
0–6 months	115	2.2
6–12 months	95	2.0
1–3 years	95	1.8
4–6 years	90	1.5
7–10 years	75	1.2
Adolescence	(male/female)
11–14 years	65/55	1.0
15–18 years	60/40	0.8

Rapid neuronal development

The brain grows rapidly during the last trimester of pregnancy and throughout the first 2 years of life. The complexity of interneuronal connections also increases substantially during this time. This process appears to be sensitive to undernutrition. Even modest energy deprivation during periods of rapid brain growth and differentiation is thought to lead to an increased risk of adverse neurodevelopmental outcome. This is not surprising when one considers that at birth the brain accounts for approximately two-thirds of basal metabolic rate, and at 1 year for about 50% (Fig. 12.2). Many studies have drawn attention to the delayed development seen in children suffering from protein-energy malnutrition due to inadequate food intake, although inadequate psychosocial stimulation may also contribute.

Figure 12.2 The relative contribution to basal metabolic rate derived from brain, liver and muscle changes with growth. Whereas the brain accounts for two-thirds of the basal metabolic rate at birth, this falls to 25% in adults. (Adapted from Halliday MA. 1971. *Pediatrics* 47(1 Suppl 2):169.)

Acute illness or surgery

A child’s nutrition may be compromised following an acute illness or surgery. Infants are prone to recurrent infections, which reduce food intake and increase nutritional demands. Following surgery, after a brief anabolic phase, catecholamine secretion is increased, causing the metabolic rate and energy requirement to increase. Urinary nitrogen losses may become so great that it is impossible to achieve a positive nitrogen balance and weight is lost. After uncomplicated surgery, this phase may last for a week, but it can last several weeks after extensive burns, complicated surgery or severe sepsis. Thereafter, previously lost tissue is replaced and a positive energy and nitrogen balance can be achieved. However, infants may not show catch-up growth unless their energy intake is as high as 150–200 kcal/kg per day compared with the normal of 95–115 kcal/kg per day.

Long-term outcome of early nutritional deficiency

Linear growth of populations

Growth and nutrition are closely related, such that the mean height of a population reflects its nutritional status. Thus, in the developed world, people have become taller. Height is adversely affected by lower socioeconomic status and increasing number of children in families. Children’s size increases amongst populations emigrating from poor to more affluent countries.

Disease in adult life

Evidence suggests that undernutrition in utero resulting in growth restriction is associated with an increased incidence of coronary heart disease, stroke, non-insulin-dependent diabetes and hypertension in later life (Fig. 12.3). There is also a similar but weaker association with low weight at 1 year of age. The mechanism is unclear, but it is recognised that fetal undernutrition leads to redistribution of blood flow and changes in fetal hormones, such as insulin-like growth factors and cortisol. Alternatively, it may be the rapid, postnatal growth (catch-up) seen in babies suffering from intrauterine growth restriction that is the causal factor.

Figure 12.3 Death rates from coronary heart disease according to birthweight showing increased rate in low birthweight babies. (After Barker DJ. 1999. Fetal origins of adult disease. *Growing up in Britain: Ensuring the Healthy Future for our Children.* A Study of 4–5 year olds. BMJ Books, London.)

Summary

Nutritional vulnerability

Infants are more vulnerable to poor nutrition because of:

• Poor stores of fat and protein

• Extra nutritional demands for growth – the weight of a term infant doubles by 4 months and trebles by 1 year.

• More frequent intercurrent illnesses that reduce food intake and increase nutritional demands.

Infant feeding

Breast-feeding

There can be no doubt that breastmilk is the best diet for babies, although the popularity of breast-feeding has frequently reflected fashion. The prevalence of breast-feeding in the UK has increased, and 78% of mothers breast-feed their infants at birth. The Department of Health guidelines in the UK, endorsing the World Health Organization recommendation, is that mothers should breast-feed exclusively for the first 6 months of life, though most are weaned to solid food before this age.

Advantages (see Box 12.1)

In developing countries, where the environment is often highly contaminated, breast-feeding dramatically improves survival during infancy as a result of reduced gastrointestinal infection. Consequently, breast-feeding is one of the four most important World Health Organization strategies for improving infant and child survival. The superiority of breast milk over modern adapted cow’s milk formulae is less easy to prove in developed countries. This is partly because it is impossible to conduct randomised studies and partly because of confounders such as social class, education and smoking.

Box 12.1 Why breast is best – the advantages of breast milk

Advantages of breast-feeding for the infant are that it:
• provides the ideal nutrition for infants during the first 4–6 months of life
• is life-saving in developing countries
• reduces the risk of gastrointestinal infection, and, in preterm infants, of necrotising enterocolitis
• enhances mother–child relationship
• reduces risk of insulin-dependent diabetes, hypertension and obesity in later life.
Advantages for the mother are that it:
• promotes close attachment between mother and baby
• increases the time interval between children, which is important in reducing birth rate in developing countries
• helps with a possible reduction in premenopausal breast cancer.
Scientific explanation of some of the properties of breast milk
Anti-infective properties
Humoral
Secretory IgA	Comprises 90% of immunoglobulin in human milk. Provides mucosal protection, but of uncertain benefit
Bifidus factor	Promotes growth of Lactobacillus bifidus, which metabolises lactose to lactic and acetic acids. The resulting low pH may inhibit growth of gastrointestinal pathogens
Lysozyme	Bacteriolytic enzyme
Lactoferrin	Iron-binding protein. Inhibits growth of Escherichia coli
Interferon	Antiviral agent
Cellular
Macrophages	Phagocytic. Synthesise lysozyme, lactoferrin, C3, C4
Lymphocytes	T cells may transfer delayed hypersensitivity responses to infant. B cells synthesise IgA
Nutritional properties
Protein quality	More easily digested curd (60 : 40 whey : casein ratio)
Lipid quality	Rich in oleic acid (with palmitate in C-2 position). Improved digestibility and fat absorption
	Enhanced lipolysis lipase.
Calcium: phosphorus ratio of 2 : 1	Prevents hypocalcaemic tetany and improves calcium absorption
Renal solute load	Low
Iron content	Bioavailable (40–50% absorption)
Long-chain polyunsaturated fatty acids	Structural lipids; important in retinal development

However, there is convincing evidence that gastrointestinal infection is less common in breast-fed infants even in developed countries. There is also evidence that human milk feeds reduce the incidence of necrotising enterocolitis in preterm infants.

Many mothers who breast-feed find that it helps them establish an intimate, loving relationship with their baby. However, establishing breast-feeding is not always straightforward, and many mothers need help and encouragement.

Breast-feeding is associated with a reduced incidence of obesity, diabetes mellitus and hypertension in later life. There is also a reduction in breast cancer in mothers who breast-feed.

Exclusive breast-feeding in early infancy is life-saving in developing countries.

Potential complications (Box 12.2)

As one cannot readily tell how much milk a baby is taking from the breast, the baby’s weight should be checked regularly, every few days in the first couple of weeks, then weekly until feeding is well established. Successful breast-feeding of twins can be achieved, but is more difficult (Fig. 12.4). It is rarely possible to totally breast-feed triplets and higher-order births. Preterm infants can be breast-fed, but the milk will need to be expressed from the breast until the infant can suck. Maintaining the supply of milk can be a problem for mothers of preterm babies.

Box 12.2 Potential complications of breast-feeding

Unknown intake	Volume of milk intake not known
Transmission of infection	Maternal CMV, hepatitis B and HIV – increases risk of transmission to the baby
Breast-milk jaundice	Mild, self-limiting, unconjugated hyperbilirubinaemia; continue breast-feeding
Transmission of drugs	Antimetabolites and some other drugs contra-indicated. Check formulary
Nutrient inadequacies	Breast-feeding beyond 6 months without timely introduction of appropriate solids may lead to poor weight gain and rickets
Vitamin K deficiency	Insufficient vitamin K in breast milk to prevent haemorrhagic disease of the newborn. Supplementation is required
Potential transmission of environmental contaminants	Nicotine, alcohol, caffeine, etc.
Less flexible	Other family members cannot help or take part. More difficult in public places
Emotional upset	If difficulties or lack of success can be upsetting

Figure 12.4 Successful breast-feeding of preterm twins.

While two-thirds of mothers in the UK initially breast-feed, this proportion rapidly declines during the first few months (Fig. 12.5). Nearly 90% of social class I mothers start breast-feeding, but only 60% of mothers from social class V. Breast-feeding is restrictive for the mother, as others cannot take charge of her baby for any length of time. This is particularly important if she goes to work and may delay her return, which may cause financial hardship for the family. Facilities for breast-feeding in public places remain limited. Failure to establish breast-feeding will sometimes cause significant emotional upset in the mother.

Figure 12.5 Prevalence of breast-feeding and proportion of infants given solid feeds during the first 9 months of life in the UK. Over the last 10 years there has been a marked increase in the prevalence of breast-feeding and delay in weaning onto solid food (Infant Feeding Survey, 2005).

Establishing breast-feeding

Colostrum, rather than milk, is produced for the first few days. Colostrum differs from mature milk in that the content of protein and immunoglobulin is much higher. Volumes are low, but water or formula supplements are not required while the supply of breast milk is becoming established.

The first breast-feed should take place as soon as possible after birth. Subsequently, frequent suckling is beneficial as it enhances the secretion of the hormones initiating and promoting lactation (Fig. 12.6).

Figure 12.6 Physiology of breast-feeding.

Primates probably do not breast-feed instinctively. Monkeys bred in captivity in zoos have to be taught how to breast-feed by their keepers. It is therefore important that breast-feeding should have as high a public profile as possible. Women who have never seen an infant being breast-fed are less likely to want to breast-feed themselves. Education in schools and during pregnancy about the advantages of breast-feeding is advantageous. Advice and support from other women who have breast-fed may be important in dealing with early problems such as engorgement or cracked nipples.

Newborn infants of mothers planning to breast-feed should ideally not be given any formula feeds.

Formula-feeding

Infants who are not breast-fed require a formulafeed based on cow’s milk. Unmodified cow’s milk is unsuitable for feeding in infancy as it contains too much protein and electrolytes and inadequate iron and vitamins. Even after considerable modification, differences remain between formula feeds and breastmilk (Table 12.2)

Table 12.2

A comparison of human milk, cow’s milk and infant formula (per 100 ml)

	Mature breast milk	Cow’s milk	Infant formula (modified cow’s milk)
Energy (kcal)	62	67	60–65
Protein (g)	1.3	3.5	1.5–1.9
Carbohydrate (g)	6.7	4.9	7.0–8.6
Casein : whey	40 : 60	63 : 37	40 : 60 to 63 : 37
Fat (g)	3.0	3.6	2.6–3.8
Sodium (mmol)	0.65	2.3	0.65–1.1
Calcium (mmol)	0.88	3.0	0.88–2.1
Phosphorus (mmol)	0.46	3.2	0.9–1.8
Iron (µmol)	1.36	0.9	8–12.5