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.

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.

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.

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.

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.

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.

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).

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.

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)

All milks currently available in the UK have been modified to make their mineral content and renal solute load comparable with that of mature human milk. Since these changes were introduced in the UK (in the 1970s), there has been an impressive reduction in the incidence of hypernatraemic dehydration in infants with gastroenteritis. There is no evidence that any one of the many brands is superior to any other.

Introduction of whole, pasteurised cow’s milk

Breast-feeding or formula-feeding is recommended until the age of 12 months, and there are advantages in continuing to 18 months of age. Pasteurised cow’s milk may be given from 1 year of age but is deficient in vitamins A, C and D and in iron, and supplementation will be required unless the infant is having a good diet of mixed solids. Alternatively, ‘follow-on’ formulae can be used. They contain more protein and sodium than infant formulae and, in contrast to cow’s milk, are fortified with iron and vitamins. Children on cow’s milk should receive full fat milk up to the age of 5 years.

Specialised infant formula

A specialised formula may be used for cow’s milk protein allergy/intolerance, lactose intolerance (primary lactase deficiency or post-gastroenteritis intolerance), cystic fibrosis, neonatal cholestatic liver disease and following neonatal intestinal resection.

In a cow’s milk-based formula, the protein is derived from cow’s milk protein, the carbohydrate is lactose and the fat mainly long-chain triglycerides. In a specialised formula, the protein is either hydrolysed cow’s milk protein, amino acids or from soya, the carbohydrate is glucose polymer and the fat a combination of medium- and long-chain triglycerides. Medium-chain triglycerides are directly absorbed into small intestine and need neither pancreatic enzymes nor bile salts for this process.

A soya formula should not be used below 6 months of age as it has a high aluminium content and contains phytoestrogens (plant substances that mimic the effects of endogenous oestrogens). There is no compelling evidence that the use of a specialised formula prevents the development of atopy (eczema, asthma, etc.).

Weaning

Solid foods are recommended to be introduced after 6 months of age, although they are often introduced earlier as parents often consider that their infant is hungry. It is done gradually, initially with small quantities of pureed fruit, root vegetables, or rice. If weaning takes place before 6 months of age, wheat, eggs and fish should be avoided. Foods high in salt and sugar should also be avoided and honey should not be given until 1 year of age because of risk of infantile botulism. After 6 months of age, breastmilk becomes increasingly nutritionally inadequate as a sole feed, as it does not provide sufficient energy, vitamins or iron.