Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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0032 In patients with disorders in which the assembly of

peroxisomes is deficient (mutations in PEX protein

complementation groups, e.g., Zellweger syndrome),

deficiency of some essential fatty acids has been docu-

mented. Enzymes required for the oxidation of very-

long-chain fatty acids (including arachidonic acid)

and in the synthesis of some polyunsaturated com-

pounds are located in the peroxisome and these are

absent or have a very low activity in these patients.

0033 PKU is a single-enzyme disease in phenylalanine

hydroxylation in which low essential fatty acid status

has been found. It is associated with neuropathy in

some patients. Circulating abnormal metabolites

affect the synthesis of n-6 (arachidonic acid) and n-3

(docosahexanoic acid) fatty acids.

0034 Secondary deficiency of essential fatty acids has

been found in relatively rare disorders causing lipid

malabsorption (transport defects, group 4 pathophy-

siology) and hereditary exocrine pancreas insuffi-

ciency. In the latter group, cystic fibrosis is the most

frequently encountered disorder. Sjo

gren–Larsson

syndrome (in which microsomal conversion of

medium- and long-chain fatty aldehydes to their carb-

oxylic acids is defective) causes a unique inactivation

in leukotriene B

inhibition. Patients have elevated

leukotriene levels and inflammatory skin changes.

Symptoms of essential fatty acid deficiency in other

patients are nonspecific and range from dermatitis to

severe failure to thrive. Diagnosis is often delayed.

Treatment of exocrine pancreas insufficiency by

pancreas enzyme supplementation often corrects the

essential fatty acid profile. In other disorders skin

ointments (on the basis of vegetable oil rich in poly-

unsaturated fatty acids) are a treatment option. The

course of several severe and fatal disorders, such as

abetaliproteinema or Zellweger syndrome (in which

oral supplementation is given), is not clearly altered

by such treatment however.

See also: Amino Acids: Properties and Occurrence;

Determination; Metabolism; Diabetes Mellitus: Problems

in Treatment; Fatty Acids: Tr a n s -fatty Acids: Health

Effects; Hyperlipidemia (Hyperlipidaemia); Nucleic

Acids: Properties and Determination; Physiology

Further Reading

Blau N, Duran M, Blaskovics ME and Gibson KM (eds)

(2003) Physician’s Guide to the Laboratory Diagnosis of

Metabolic Diseases. London: Springer.

Fernandes J, Saudubray JM and van den Berghe G (eds)

(2000) Inborn Metabolic Diseases. Berlin: Springer.

Leonard JV and Morris AAM (2000) Inborn errors of

metabolism around time of birth. Lancet 356: 583–587.

Scriver CR, Beaudet AL, Sly WS et al. (eds) (2001) The

Metabolic and Molecular Bases of Inherited Disease,

8th edn. New York: McGraw-Hill.

INFANT FOODS

Contents

Milk Formulas

Weaning Foods

Milk Formulas

D Hileti-Telfer, The Hospitals for Sick Children,

London, UK

Background

0001 Until the early 1900s, there was no alternative to

human breast milk for feeding newborn infants. Con-

sequently, over 80% of infants were breast-fed. If a

mother was unable to breast-feed her baby, a wet

nurse had to be found, or diluted cow’s milk had to

be given. The 1940s marked a major turning point

in the history of infant feeding in the UK, with an

increasing proportion of babies being bottle-fed. A

number of social, economic, and practical factors

contributed to this radical change in infant feeding

practices. The major influence was the introduction

of the Welfare Food Scheme during World War II.

This allowed mothers and children to have free or

subsidized National Dried Milk (NDM) at a time

when cows’ milk was rationed. Inevitably, the use of

NDM spread to infants and escalated as social atti-

tudes gradually changed towards women working

outside the home.

0002Unfortunately, NDM and most commercial infant

formulas available over the succeeding years were not

3270 INFANT FOODS/Milk Formulas

adapted to meet the specific nutritional and physio-

logical needs of newborn infants. Excess concentra-

tions of sodium, chloride, phosphorus, and calcium

caused many problems, including hypernatremic

dehydration, neonatal tetany, and even death in

some infants. It is only recently, with advances in

food technology, that infant formulas have been

developed, providing an acceptable alternative to

human milk.

Need for Infant Formulas

0003 Humans are the only mammals who have attempted

to feed their young on something other than their own

milk. It is now recognized that suitable infant formu-

las must be made available for infants whose mothers

choose not to breast-feed or are unable to establish

lactation, or where breast-feeding is contraindicated

owing to a medical condition, such as galactosemia

and congenital alactasia.

0004 Despite the well-documented advantages of breast-

feeding, many women choose not to breast-feed. The

UK Office of National Statistics (ONS) 1995 Infant

Feeding Survey showed that 39% of mothers gave

infant formula from birth, and by 6 weeks, 62% of

infants were exclusively bottle-fed. One of the main

differences between the ONS surveys of 1990 and

1995 was the decrease in the use of cow’s milk at 8

months from 42% in 1990 to 16% in 1995 owing to

the continued use of milk formulas.

0005 In the UK, mothers who are carriers of the human

immunodeficiency virus (HIV) are discouraged from

breast-feeding, as the virus can be passed to an infant

via the breast milk. Breast-feeding by HIV mothers is

not, however, discouraged in less developed countries

such as sub-Saharan Africa, where safe preparation

and provision of infant formulas cannot be ensured.

Maternal medication can also be found in breast milk.

Even low doses of some drugs need to be avoided

during lactation, including those that are radioactive,

cause allergy or bleeding disorders, are poorly metab-

olized by the newborn, or inhibit lactation. The rela-

tive risks of drugs that pass into the breast milk are

reviewed annually in the British National Formulary.

If a suitable alternative drug is not available, a mother

would need to use an infant formula.

Compositional Guidelines

0006 The composition of all infant formulas in the UK

comply with the guidelines of the COMA report

‘Artificial Feeds for the Young Infant’ and the legal

requirements of ‘The Infant Formula and Follow-on

Formula Regulations 1995’. The 1995 regulations

implement the European Commission Directives

91/321/EEC and Council Directive 92/52/EEC, and

represent the first mandatory controls on compos-

ition and marketing of infant and follow-on formulas.

They set upper and lower limits for the concentration

of most nutrients in a reconstituted feed (Table 1).

tbl0001Table 1 Compositional guidelines for infant and follow on

formulas

Infant

formulas

Follow-on

formulas

Major nutrients

Energy (kcal per 100 ml) 60 – 75 60–80

Protein (g per 100 kcal) 2.25–3

;

1.8–3

;

2.25–3

2.25–4.5

Taurine (mmol per 100 kcal) 42

L-Carnitine (mmol per 100 kcal)  7.5

Lipids (g per 100 kcal) 3.3–6.5 3.3–6.5

Linoleic acid (mg per 100 kcal) 300–1200 300

a-Linolenic acid (mg per 100 kcal) 50

Linoleic/a-linolenic acid ratio 5–15

Carbohydrate (g per 100 kcal) 7–14 7–14

Minerals

Sodium (mg per 100 kcal) 20 – 60

Potassium (mg per 100 kcal) 60 – 145

Chloride (mg per 100 kcal) 50 – 125

Calcium (Ca) (mg per 100 kcal) 50

Phosphorus (P) (mg per 100 kcal) 25 – 90

Ca:P ratio 1.2–2 2

Magnesium (mg per 100 kcal) 5 – 15

Iron (mg per 100 kcal) 0.5 – 1.5

;

1–2

Zinc (mg per 100 kcal) 0.5–1.5

;

0.75 – 2.4

0.5

0.75

Copper (mg per 100 kcal) 20–80

Iodine (mg per 100 kcal) 5 5

Selenium (mg per 100 kcal) 3

Vitamins

Retinol (mg per 100 kcal) 60 – 180 60 – 180

Cholecalciferol (mg per 100 kcal) 1–2.5 1–3

Thiamin (mg per 100 kcal) 40 nr

Riboflavin (mg per 100 kcal) 60 nr

Nicotinamide (mg per 100 kcal) 800 nr

Pantothenic acid (mg per 100 kcal) 300 nr

Vitamin B

(mg per 100 kcal) 35 nr

Biotin (mg per 100 kcal) 1.5 nr

Folic acid (mg per 100 kcal) 4nr

Vitamin B

(mg per 100 kcal) 0.1 nr

Vitamin C (mg per 100 kcal) 8 8

Vitamin K (mg per 100 kcal) 4nr

a-Tocopherol 0.5 0.5

(mg per gram of polyunsaturated

fatty acids expressed as

linoleic acid)

Unmodified cow’s milk.

Modified cow’s milk.

Soya milk.

Concentrations at least equal to those found in cow’s milk, reduced in the

same ratio as the protein concentration of the follow-on formulas to that of

cow’s milk.

nr, no recommendation.

Data from MAFF (1995) The Infant Formula and Follow-on Formula

Regulations 1995, No. 77. London: HMSO.

INFANT FOODS/Milk Formulas 3271

In setting these, the normal physiology of young

infants and biological availability of nutrients were

considered, but the composition of mature human

milk provided the main reference standard. Cur-

rently, 10 infant formulas based on cows’ milk are

available in the UK.

Types of Infant Formulas

0007 Infant formulas should provide the sole source of

nutrition during the first few months of life. Although

manufacturers can now simulate the nutrient com-

position of mature breast milk, they are unable to

reproduce other aspects such as its enzyme content

or immunological properties. Normal infant formulas

are manufactured from cows’ milk, but this requires

substantial alteration to parallel the composition of

breast milk (Table 2). These modifications are a

reduction in protein and minerals, an increase in

carbohydrate, and the addition of vitamins and

trace elements. Extra iron and zinc need to be

added, owing to their poor absorption from cow’s

milk. Vitamin activity may be lost during the

manufacturing process or on storage, and this must

be compensated for.

0008 The other adaptions made to cows’ milk are to im-

prove its absorptive characteristics, which is achieved

by altering the casein:whey ratio and fat blend.

0009 The protein in cow’s milk is predominantly casein,

with a whey:casein ratio of 20:80. Two categories of

infant formulas are produced: whey-dominant and

casein-dominant. The newborn infant more readily

absorbs whey protein. Whey-based milks are a mixture

of demineralized whey and a small amount of skimmed

milk, which achieves a whey:casein ratio similar to

breast milk (60:40). The use of whey proteins alters

the amino acid pattern, making it closer to human milk.

In addition, demineralization of the whey reduces the

sodium, potassium, and phosphate contents.

0010Casein-dominant milks are manufactured using

skimmed milk and in a few, full-cream milk as the

protein source. Their whey:casein ratio is the same as

cows’ milk. Although substantially modified during

manufacture, the levels of sodium, phosphorus and

potassium are usually higher than in whey-dominant

milks.

0011In recent years, studies have indicated that young

infants may have an impaired ability to synthesize

taurine and carnitine, and a dietary source is therefore

required. Carnitine is necessary for the transport of

long-chain fatty acids into the mitochondria, where

they undergo b-oxidation. Artificial formulas based

on cows’ milk contain adequate amounts of carnitine,

without the need for fortification. Taurine has a

major role in the conjugation of bile acids, which is

essential for fat absorption, and it may be involved in

retinal, cardiac, and central nervous system function.

Cows’ milk contains a low concentration of taurine.

Infant formulas are now fortified with taurine to a

level similar to that found in breast milk (3.3–5.2 g

per 100 ml).

0012The carbohydrate present in cows’ milk and human

milk is lactose. Extra carbohydrate must be added to

cows’ milk to equate with human milk. This is usually

added in the form of lactose, but maltodextrins and

occasionally amylose are used in casein-dominant

milks. Lactose enhances calcium absorption and

helps to inhibit the growth of gut pathogens by fer-

mentation in the colon. Lactose and maltodextrins

are efficiently digested and absorbed by the young

infant, but the situation with amylose is less clear.

Sucrose is rarely used in infant formulas, as it would

make the feed very sweet compared with breast milk,

and it is also more cariogenic. Glucose and other

monosaccharides are avoided, as they would signifi-

cantly increase the feed osmolality.

0013The concentrations of fat in mature breast milk and

cows’ milk are similar. However, the chemical com-

position, in terms of degree of saturation, chain

length, and configuration of fatty acids on the trigly-

ceride molecule is different. These differences influ-

ence fat absorption. Short and medium-chain fatty

acids are more efficiently absorbed than saturated

fatty acids of the same chain length. In both milks,

palmitic acid is the most common saturated fatty

tbl0002 Table 2 Comparison between cow’s milk and mature human

milk

Cow’s milk (per 100 ml) Mature

human milk

(per100 ml)

Energy (kcal) 66 69

(kJ) 275 289

Carbohydrate (g) 4.8 7.2

Protein (g) 3.2 1.3

Fat (g) 3.9 4.1

Sodium (mmol) 2.4 0.6

Potassium (mmol) 3.6 1.5

Calcium (mmol) 2.9 0.9

Phosphorus (mmol) 3.0 0.5

Zinc (mmol) 6.1 4.6

Iron (mmol) 0.9 1.3

Vitamin D (mg) 0.03 0.04

Vitamin C (mg) 1.0 4

Vitamin B

(mg) 0.04 0.02

Vitamin B

(mg) 0.17 0.03

Nicotinic acid (mg) 0.1 0.2

Vitamin E (mg) 0.09 0.34

Vitamin A (mg) 52 58

Data from Holland B, Welch AA, Unwin ID et al. (1991) McCance and

Widdowson’s The Composition of Foods, 5th edn. Cambridge: Royal Society

of Chemistry.

3272 INFANT FOODS/Milk Formulas

acid. In human milk, palmitic acid is mainly in the 2

position on the triglyceride molecule, and this is

absorbed more easily than palmitic acid in the 1 and

3 positions, as found in cows’ milk.

0014 No single fat source can adequately reflect the

characteristics of the fat profile in mature breast

milk, so a blend is used. Most manufacturers use a

mixture of vegetable oils.

0015 The fat source must also provide the essential fatty

acids linoleic (C18:2, o -6) and a-linolenic acid

(C18:3, o-3). Current research suggests that a balance

between these two fatty acids is necessary, as excess

linoleic acid suppresses the formation of a-linolenic

acid derivatives. A ratio of 5:1 of o-6:o-3, as occurs

in breast milk, is being suggested. However, there is a

need for more short- and long-term studies before the

optimum ratio and its effects on growth are evalu-

ated. Not all infant formulas provide a ratio of 5:1.

0016 Linoleic and a-linolenic acid are the precursors

of the very-long-chain (C20–C22) polyunsaturated

fatty acids (LCPUFA), arachidonic and docosahexa-

enoic acid. LCPUFA are involved in the neural and

vascular development of the fetus and neonate and

are present in human milk. Recently, there has been

much interest in the possible benefits of the addition

of LCPUFA to infant formulas. A recent systematic

review concluded that o-3 LCPUFA increases the

early visual maturation in preterm infants, but no

long-term benefit has been shown for preterm infants

receiving formula supplemented with LCPUFA. How-

ever, another systematic review prepared by the same

author, examining the effect of LCPUFA supplemen-

tation in term infants, concluded that there is little

evidence that it confers any benefit on visual or cog-

nitive development. Currently, some, but not all,

infant formulas are supplemented with LCPUFA.

0017 Nucleotides, a component of the nonprotein nitro-

gen in human milk, may be important for normal

immune function. Nucleotides can also be synthe-

sized endogenously. Nucleotide nitrogen accounts

for 0.1–0.15% of the total nitrogen content of

human milk, but is present in much smaller concen-

trations in cows’ milk-based formulas. Supplemen-

tion of infant formulas with nucleotides seems to be

beneficial in clinical trials, although further research

is needed before routine nucleotide supplementation

of infant formulas can be considered.

0018 Since 1984, a further range of formulas have been

manufactured known as ‘follow-on’ milks. These are

based on cows’ milk and are intended for use from 6

months of age in the UK, as part of mixed feeding.

They are not suitable as a replacement for either

breast milk or infant formulas before this age.

0019 ‘Follow-on’ milks have a higher protein and iron

content than infant formulas, but the energy density is

similar. The main 1995 compositional guidelines for

infant and ‘follow-on’ formulas set by the European

Commission Directives 91/321/EEC and 92/52/EEC

are shown in Table 1. The iron, calcium, and sodium

contents are higher than in infant formulas. Gener-

ally, all brands are supplemented with the full range

of vitamins and minerals.

0020Soya infant formulas are manufactured from soya

protein isolate and used for infants on cows’ milk-free

diet. Their carbohydrate source is a glucose polymer,

and the protein is derived from soy. They are supple-

mented with methionine, carnitine, minerals, vita-

mins, and trace elements, so that the available

nutrients are similar to those in human milk (Table 1).

Production

0021Advances in food technology since the early 1960s

have enabled manufacturers to produce infant formu-

las that are in line with present scientific knowledge

about infants’ nutritional requirements.

0022Infant formulas are typically composed of the

following: skimmed milk, demineralized whey (in

whey-dominant formulas only), a carbohydrate

source, fat blend, and vitamins and minerals. Each

raw material undergoes stringent quality-control

checks on arrival at the factory and throughout

all stages of manufacture. These tests are for nutri-

tional composition, purity, microbiological safety,

and physical properties. The manufacturing process

and the cleaning of the manufacturing plant are

partially or fully automated.

0023Production methods vary, but all aim to blend the

raw ingredients together to produce a safe, homoge-

neous, and stable powder or liquid. A typical example

of an infant formula manufacture is as follows:

0024Pasteurized skimmed milk is bought in as liquid or

powder. On arrival, the liquid milk is usually repas-

teurized by heating to 72



C for 15 s, which destroys

about 90% of all microorganisms present. Through-

out the manufacturing process, the product is repas-

teurized several times. Whey is purchased in a

demineralized form or is demineralized on site. The

technique of demineralization, which was perfected

in the 1960s, was a major advance in infant formula

production and is performed by electrodialysis,

ultrafiltration, or ion exchange. The repasteurized

skimmed milk and demineralized whey are mixed

with the carbohydrate source, vitamin premix, min-

erals, and the fat blend. The minerals required will

vary, depending on their concentration in other raw

materials. The fat-soluble vitamins are usually added

to the fat prior to this process.

0025The bulk ingredients usually undergo centrifugal

clarification, to remove small particle matter, and

INFANT FOODS/Milk Formulas 3273

then homogenization to ensure that all the particles

are uniform in the final product. The liquid infant

formula is further subjected to two heat processes:

pasteurization and heating to a suitable temperature

for spray-drying. Spray-drying produces a powder

that will reconstitute easily into solution. Some com-

panies use additional wetting and drying cycles

to form granules, which, they claim, are easier to

measure and dissolve.

0026 In the UK, powdered infant formulas are packaged

in a protected atmosphere using an inert gas to help

remove the oxygen, thus reducing any oxidation of

the powder. On the packing production line, the cans

(already sealed at one end) are inverted and subjected

to intense blower and vacuum systems to remove any

contamination. A machine drops the measuring

scoop into the can, prior to filling with powder. Air

is then removed from the pack and replaced with an

inert gas mixture, and the container is sealed. Foil

sachets are filled in a similar manner. The shelf-life

is 2–3 years for sealed tins and 15 months for sachets;

when opened, tins need to be used within 4 weeks,

and foil sachets within 2 weeks.

0027 Several companies produce ready-to-feed (RTF)

infant formulas for community and hospital use.

Glass bottles (100 ml) are produced for hospital

use and laminated cartons (250 and 1000 ml) for

home use. The major ingredients are the same as

those used in powdered infant formula production.

For the production of RTF bottles, the liquid is pro-

duced using water that has been ultrafiltered or de-

ionized to remove all mineral elements. The feed is

then repasteurized and decanted into bottles, capped,

and sealed. Finally, the bottles undergo terminal

sterilization in a rotary autoclave.

0028 For the production of RTF cartons, milk is sub-

jected to UHT sterilization. This quick, high-

temperature process (typically 142



C for 2 s) aims

to retain flavor (by reducing caramelization) and

allows an extended shelf-life. The cartons are multi-

laminate, composed of polyethylene, aluminum, and

cardboard layers. The base is heat-treated and the

packs sterilized internally by hot hydrogen peroxide,

before being aseptically filled with milk. The manu-

facturers recommend that opened 250-ml cartons are

used within 24 h, and opened 1000-ml cartons

are used within 48 h. The quality checks on these

products are extensive, possibly more so than

those performed on powders, with up to 5% of the

final product destructively tested.

Preparation

0029 In response to the 1974 government recommenda-

tion, reconstitution of infant formula in the UK was

standardized, requiring only the addition of water.

Previously, feed reconstitution was not uniform,

which sometimes resulted in over- or underconcentra-

tion of feeds. Nowadays, the dilution is always one

level scoop of powder added to 30 ml (1 fl. oz.) of

water. Scoops from different brands are not inter-

changeable. However, the relative risk from using

the wrong scoop is minimal, unless a scoop for granu-

lated powder is used for measuring nongranulated

powder (or vice versa).

0030Freshly boiled water that has been allowed to

cool should be used to reconstitute infant formulas.

Domestic softened water, or water repeatedly boiled,

is unsuitable, owing to unacceptably high levels

of certain minerals. Water filters remove organic

compounds, chlorine, and pesticides from water.

The resulting water may not be microbiologically

safe once the chlorine has been removed, and must

therefore be boiled prior to use in feed preparation.

Some bottled waters have an unacceptably high

sodium content; only those that contain 20 mg

of sodium per liter or less, should be used for reconsti-

tuting infant formulas. They will also require boiling

before use, as they are not sterile.

0031Immediately before preparing feeds, hands and

work surfaces need to be thoroughly washed. Written

and pictorial instructions for reconstituting milk

powders are given on all infant feed packaging. The

first stage is to measure the cooled, boiled water into

a graduated milk bottle. The optimum temperature

for the water is usually about 50



C, as this achieves

the best dissolution, but specific instructions are given

for each formula. The powder is heaped naturally, not

compressed, into a scoop and leveled off with the

straight edge of a clean knife or spatula. The appro-

priate number of scoops are added to the water, the

cap replaced, and the bottle shaken to achieve thor-

ough mixing of the feed. This can be fed to the infant

or kept refrigerated for a maximum of 24 h. Feeds can

be warmed by standing the bottle in a jug of hot

water. Microwave ovens should not be used for this

purpose, as they may result in uneven heating and risk

scalding the baby. The temperature of warmed feeds

can be checked by testing a few drops on the inside of

the wrist.

Sterilization

0032Bottle-fed babies do not have the same degree of

immunological protection as those that are breast-

fed, and so strict attention to hygiene practices is

vital during feed preparation.

0033Used bottles and equipment should be thoroughly

washed in warm, soapy water, using a bottle brush, if

necessary, to remove all traces of milk, then rinsed in

3274 INFANT FOODS/Milk Formulas

cold water and sterilized. Sterilization is most com-

monly performed by the addition of sterilizing tablets

or liquid to water to produce a hypochlorite steriliz-

ing solution. All bottles and equipment, except metal-

lic objects, need to be completely immersed for the

time specified by the manufacturer. To ensure com-

plete sterilization, the bottles should not contain any

air bubbles or milk residues. A fresh solution must be

made every 24 h.

0034 Alternatively, items can be disinfected by boiling

for 20 min in a lidded saucepan kept exclusively for

this purpose. Again, the bottles must be fully sub-

merged and free of air bubbles. Teats need only be

boiled for 5 min.

0035 Steam sterilization at home is a fairly recent innov-

ation, relying on moist heat as the means of disinfec-

tion. Several companies now produce simple electric

steam sterilization units. Steam is generated by the

addition of a small amount of water on to a heated

base-plate; the water gradually turns to steam, steril-

izing the bottle surfaces. The machine automatically

switches off on completion of its 6–12-min cycle. A

temperature in excess of 98



C is achieved for 3 min.

This conforms with the current UK Department of

Health standards for equipment used for disinfection:



C for a minimum of 1 min. Microwave ovens are

not effective for sterilizing equipment.

Marketing

0036 The Infant Formula and Follow-on Formula Regula-

tions regulates the marketing of milk formulas.

Before this was adopted, manufacturers adhered to

the Food Manufacturers’ Federation code of practice.

This was a voluntary code compiled by the infant

formula manufacturers in consultation with the Min-

istry of Agriculture, Fisheries and Food and the

Department of Health and was based on the Inter-

national Code of Marketing of Breast Milk Substi-

tutes. The main recommendations of the code are as

follows: advertising of infant formulas should be re-

stricted to publications, which are distributed by

health care professionals; all packaging and advertise-

ments should clearly state the superiority of breast-

feeding; the provision of free samples of formulas to

mothers should be prohibited; and maternity hos-

pitals should not promote the use of infant formula.

Furthermore, in 1989, the UK government advised

that RTF infant formulas should no longer be subsid-

ized for National Health Service hospitals as the

availability of these cheap products undermined

breast-feeding practices. These are now purchased at

a price decided by national contract. The WHO code

is endorsed by most industrialized countries, but it is

not universally implemented.

See also: Fatty Acids: Tr a n s -fatty Acids: Health Effects;

Heat Treatment: Ultra-high Temperature (UHT)

Treatments; Infants: Breast- and Bottle-feeding; Milk:

Dietary Importance; Powdered Milk: Characteristics of

Milk Powders; Sterilization of Foods

Further Reading

Carver JD (1994) Dietary nucleotides: cellular immune,

intestinal and hepatic system effects. Journal of Nutri-

tion 124 (1 supplement): 144S–148S.

Cosgrove M (1998) Perinatal and infant nutrition: Nucle-

otides. Nutrition 14: 748–751.

Department of Health and Social Security (1977) The Com-

position of Mature Human Milk. Report on Health and

Social Subjects 12. London: HMSO.

Department of Health and Social Security (1980) Artificial

Foods for the Young Infant. Report on Health and Social

Subjects 12. London: HMSO.

FMF (1983) Code of Practice for Marketing of Infant

Formulae in the United Kingdom and Schedule for a

Monitoring Committee. London: Food Manufacturers’

Federation (now Food and Drink Federation).

Foster K, Lader D and Cheesbrough S (1995) Infant Feed-

ing. London: Office for National Statistics, The Station-

ary Office.

Gibson RA, Makrides M, Newmann MA et al. (1994)

Ratios of linoleic acid to alpha-linolenic acid in formulas

for term infants. Journal of Pediatrics 125: S48–S55.

Jensen CL, Prager TC, Fraley JK et al. (1997) Effect of

dietary linoleic/alpha-linolenic acid ratio on growth

and visual function of term infants. Journal of Pediatrics

131: 200–209.

Joint FAO/WHO Food Standards Programme Codex Ali-

mentarius Commission (1976) FAO/WHO Recom-

mended International Standards for Foods for Infants

and Children. Rome: Food and Agriculture Organiza-

tion.

MAFF (1995) The Infant Formula and Follow-on Formula

Regulations 1995, No. 77. London: HMSO.

MAFF (1997) The Infant Formula and Follow-on Formula

(Amendment) Regulations 1997, No. 451. London:

HMSO.

Makrides M, Newmann MA, Jeffrey B, Lien EL and Gibson

RA (2000) A randomized trial of different ratios of

linoleic to alpha-linolenic acid in the diet of term infants:

effects on visual function and growth. American Journal

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Weaning Foods

A M Fehily, Tinuviel Software, Warrington, UK

Introduction

0001 Weaning is the name given to the process by which

infants progress from a diet composed only of breast

milk or infant formula milk to a family diet containing

a wide variety of foods. This is necessary to insure that

nutrient intakes continue to be adequate for healthy

growth and development throughout childhood.

0002 Infants vary in the age at which they are ready for

weaning. Advice from medical experts is that the ma-

jority of infants should not be given solid foods before 4

months of age and that a mixed diet should be offered

by 6 months of age. Ideal first foods are rice- or maize-

based cereals, fruit, vegetables, and potatoes. The range

of foods offered can then be gradually increased, such

that by the age of 1 year the diet should be mixed and

varied. (See Infants:Weaning.)

0003 This article discusses the types of foods used during

weaning, special diet considerations, the nutrient

composition of weaning foods, legislation require-

ments for the composition of commercial weaning

foods, and methods of preparation of weaning foods.

Consistency and Taste

0004 At the start of weaning, foods should be of a very

smooth, thin consistency such that they can be sucked

from a spoon. The food needs to be sufficiently liquid

for the infant to transfer it to the back of the mouth

for swallowing, but not so runny that it becomes

unmanageable. Foods should be of small particle

size and have a bland flavor. At this stage, the aim is

to introduce the infant to a wide variety of tastes.

0005 As weaning progresses, the infant is introduced to

an increasing variety of foods, providing a range of

tastes and textures. Once the infant has become used

to taking food from a spoon, pure

ed foods of a

thicker consistency can be introduced, and later

foods with small soft lumps and soft finger foods.

From about 1 year of age, most infants will be

enjoying a regular pattern of meals and snacks made

up of family foods.

Types of Foods

0006During weaning the infant is introduced to a wide

variety of foods. In this way, the eventual diet is

more likely to provide all the nutrients needed for

continued healthy growth and development. A few

foods are worthy of special mention and these are

discussed below.

Cows’ Milk

0007The UK Department of Health recommends that

whole cows’ milk should not be used as the main

milk drink for infants under the age of 1 year. This

is because the main drink makes a major contribution

to overall nutrient intakes of infants and cows’ milk is

not a good enough source of iron or zinc.

0008The Department of Health advises that semi-

skimmed milk should not be used as the main milk

drink before 2 years of age and that skimmed milk

should not be used as the main milk drink before 5

years of age. This is because milk provides a signifi-

cant proportion of a child’s energy intake, and if

skimmed or semiskimmed milk is used as the main

drink it may be difficult to insure that total daily

energy intake is sufficient.

0009This advice only applies to the use of these milks as

the main drink. It does not apply to the small amounts

of milk used in composite dishes. Milk and dairy

products are a very important part of a young child’s

diet, providing an excellent source of protein and

calcium. The use of milk and milk products as part

of the weaning diet helps to accustom the infant to

this important group of foods.

Eggs

0010For infants, eggs should be thoroughly cooked until

the white and yolk are solid.

Meat and Fish

0011Meat, especially poultry, should be thoroughly

cooked. For meat and fish, care needs to be taken to

insure that no traces of bone remain in the food.

Nuts and Seeds

0012For infants and young children, nuts and seeds should

be finely ground and not whole, to prevent choking.

0013Where there is a family history of allergy, the

Department of Health advises that peanuts and

peanut products should be avoided for the first 3

years.

Honey

0014It has been recommended that honey should not be

given to children under 1 year of age. This is because

honey is a known source of certain bacterial spores

3276 INFANT FOODS/Weaning Foods

(Clostridium botulinum). In older children and adults,

the natural gut flora suppresses the growth of these

spores. However, an infant’s gut flora may not

adequately suppress the growth of these spores.

Salt

0015 Salt (sodium chloride) is the major source of sodium

in the diet of older children and adults. However,

infants are less efficient than adults in excreting an

excess of sodium in the diet. This is because their

kidneys are not fully mature. Salt should therefore

not be added to baby foods.

0016 In the UK, commercial baby foods have no added

salt. However, many foods intended for older chil-

dren and adults contain added salt and are therefore

not suitable for infants.

Sugar

0017 Frequent consumption of sugary foods can increase

the risk of tooth decay.

0018 Sugar should only be added to baby foods where

this is necessary to provide an acceptable flavor, and

the amount added kept to the minimum required. For

example, a dessert such as chocolate pudding would

taste bitter if no sugar were added.

0019 Many foods contain sugars which are naturally

present, e.g., fruits, fruit juices, vegetables, and

milk. Both added sugar (table sugar or sucrose)

and sugars naturally present in foods such as fruits

and fruit juices can increase the risk of tooth decay if

care is not taken in use of these foods. Frequent

consumption of these foods should be avoided.

Good dental hygiene is also very important: tooth

cleaning should start as soon as teeth appear.

Additives

0020 Foods intended for older children and adults may

contain additives such as artificial colors, preserva-

tives, artificial flavors, and sweeteners. Such foods are

unsuitable for infants. These additives are not used in

commercial baby foods.

0021 There are some additives legally permitted for use

in weaning foods within the European Union (EU).

For example, natural flavorings such as vanilla are

sometimes used. Certain emulsifiers may be used

where needed to insure complete dispersion of oils

and fats.

0022 Modified starches are sometimes used to insure

that products have the right consistency. These

cross-linked amylopectin starches are used in prefer-

ence to native starches as they perform better in

the manufacturing process and do not lose their

thickening properties. The amount used is small and

the starch is easily digestible by the infant.

Special Diets

0023The Department of Health advises that where there is

a family history of atopy or gluten enteropathy,

mothers should be encouraged to breast-feed for 6

months or longer. Weaning before 4 months should

particularly be discouraged and the introduction

of foods traditionally regarded as allergenic, for

example cows’ milk and egg, should be delayed until

6 months at the earliest. For peanuts and peanut

products, advice is that, where there is a family

history of allergy, these should be avoided for the

first 3 years.

0024For the vast majority of infants, where there is no

family history of allergy, there is no need to restrict

the weaning diet.

0025It is important to note that the avoidance of any

food increases the risk that the infant may not get

enough of all the nutrients he or she needs for healthy

growth and development. Thus, if it is necessary to

exclude any food from an infant’s diet, it is essential

that expert nutritional advice is obtained from a state-

registered dietitian.

0026For infants being weaned on to a vegetarian diet,

care needs to be taken to insure that the quantity and

quality of protein are adequate and that energy intake

is adequate. Special care also needs to be taken to

avoid iron deficiency.

0027If using commercial baby foods, it is usually easy to

identify products suitable for a milk-free, egg-free,

gluten-free, or vegetarian diet, as labels of suitable

products often carry a statement to this effect.

Nutrient Composition

0028The nutrient requirements of infants differ from those

of older children and adults and are high relative to

body size. (See Infants: Nutritional Requirements.)

0029A healthy diet recommended for older children and

adults, i.e., low in fat and saturates and high in fiber,

is not appropriate for infants.

0030Weaning accustoms the infant to a wide range of

tastes and textures. As solid foods form an increasing

part of the diet, the diet becomes varied and the

nutrient density increases. This helps to insure con-

tinuing adequate nutrient intakes for healthy growth

and development.

0031At the start of weaning, the nutrient composition of

the foods is not very important as the amounts of

foods consumed are small. As weaning progresses

and solid foods make a larger contribution to overall

nutrient intake, the nutrient composition of weaning

foods becomes more important. Nevertheless, milk

continues to make a substantial contribution to over-

all nutrient intake throughout early childhood.

INFANT FOODS/Weaning Foods 3277

Energy and Protein

0032 An adequate energy intake is essential for healthy

growth and development. If energy intake is inad-

equate, dietary protein may be broken down by the

body and used to supply energy instead of being used

for growth.

0033 An adequate intake of protein, with a proper

balance of essential amino acids, should also be in-

sured during weaning. The protein content of the

diet needs to be sufficient to support the fast growth

rate of the infant, but not so much as to put a strain

on the excretory capacity of the infant’s immature

kidneys. If the diet is restricted for any reason, care

needs to be taken to insure that a variety of foods is

offered at each meal, providing a mixture of protein

sources.

0034 All foods provide energy, the best sources being

milk, rice, pasta, potatoes, bread, meat, poultry,

fish, eggs, cheese, beans, and lentils. The main sources

of protein in the diet are meat, poultry, fish, milk,

cheese, eggs, cereals, beans, peas, and lentils.

Carbohydrate

0035 Carbohydrate includes starch and sugars and these

are important sources of energy. Sugars also enhance

the palatability of the diet.

0036 Starch is found in foods such as rice, pasta, pota-

toes, and bread. Apart from table sugar (sucrose),

sugars are naturally present in many foods such as

fruits, fruit juices, vegetables, and milk. Fruits, fruit

juices, and vegetables contain fructose, glucose, and

sucrose. Milk contains lactose.

0037 Care needs to be taken in the use of sugary foods,

whether the sugar is added or is naturally present in

foods such as fruits and fruit juices, to minimize the

risk of tooth decay. Frequent consumption of these

foods should be avoided and good dental hygiene is

essential.

0038 Fruit juices and other sugary drinks should not be

allowed to remain in the mouth for long periods. In

the UK, the labels of fruit juices and similar drinks

intended for infants carry advice supported by the

British Dental Association to insure appropriate use

of these drinks:

0039 Always follow the manufacturer’s instructions on

usage and dilution

0040 Serve only at meal times and keep drinking times

short

0041 Never leave infants alone with any drink

0042 Never use drinks on a dummy or as a comforter

0043 Ideally serve from a spoon, trainer cup, or beaker,

but not from a bottle

0044 Do not give at bedtime or during the night.

Fat

0045For adults, a healthy diet is one that is low in fat. This

is not true for infants. Fat is an important source of

energy in an infant’s diet. If total fat intake is low,

it can be difficult to insure that energy intake is

adequate for healthy growth and development.

0046Fat is also an important source of essential fatty

acids and of fat-soluble vitamins (A and D). Essential

fatty acids are necessary for growth and for maintain-

ing the skin in a healthy condition. Vitamin A is

essential for vision and for healthy skin. Vitamin D

helps the body to absorb calcium, which is essential

for healthy bones.

Vitamins and Minerals

0047One of the best ways of insuring that an infant’s

intake of vitamins and minerals is adequate is to

offer a wide variety of foods.

0048Two nutrients are worthy of special note: iron and

vitamin C. Infants have high iron requirements and it

can be difficult to insure that intake is sufficient. Iron

deficiency results in anemia and may also result in

impaired mental and physical development. The

effects of deficiency may be long-lasting.

0049Iron is better absorbed from meat and meat prod-

ucts, particularly red meat (heme iron), than from

vegetable sources (nonheme iron). Some components

of the diet bind to iron and thereby hinder iron ab-

sorption: phytic acid from cereals, legumes, and other

vegetables; phosphoproteins in cows’ milk and egg

yolk; tannin in tea; and polyphenols in spinach and

coffee. Vitamin C, on the other hand, improves the

absorption of iron from the diet. Vitamin C also

enhances the absorption of other minerals from the

diet – zinc and copper. Protein also helps to improve

iron absorption, by reducing the inhibitory effect of

phytic acid.

0050Foods containing iron, particularly heme iron and

foods containing vitamin C, are therefore important

components of a weaning diet. Meat, eggs, beans,

lentils, peas, bread, and dark green vegetables provide

the main sources of iron in the diet. Fruits, vegetables,

and fruit juices provide vitamin C. Some commercial

weaning foods have added iron and many have added

vitamin C.

Fiber

0051Fiber is an important part of a healthy diet for adults.

This is not the case for infants. A high-fiber bran cereal,

for example, would not be appropriate for infants. This

is because fiber makes the diet more bulky. If the fiber

content of the diet is high, the infant may feel full after

eating fewer calories. It may therefore be difficult for

3278 INFANT FOODS/Weaning Foods

him or her to obtain sufficient energy to insure healthy

growth and development.

Commercial Weaning Foods

0052 A wide variety of commercial weaning foods is avail-

able. Weaning foods in cans and jars are available

either as homogeneous pure

es for young infants

(4–6 months of age), or preparations with larger par-

ticle size for older infants (from about 7 months of

age). A wide range of dried weaning foods is also

available, some intended for infants from about 4

months of age and others intended for infants from

about 7 months of age.

0053 Types of product available include baby rice cereal,

breakfast recipes, savoury recipes, desserts, rusks,

and drinks. Breakfast recipes are composed mainly

of fruits and cereals. Savoury varieties are composite

dishes containing ingredients such as meats, fish,

vegetables, and cereals. Dessert varieties consist of

fruits, dairy products, and cereals. Available drinks

include pure fruit juices with added vitamin C and

purified water with a hint of fruit flavor.

0054 Within the EU, there is legislation governing the

composition and labeling of processed cereal-based

foods and baby foods for infants and young children,

i.e., foods intended for children up to 3 years of

age. Details of the compositional requirements are

presented in Tables 1 and 2. Some companies also

have their own additional nutritional guidelines for

weaning foods to insure that these foods help mothers

to provide a varied and nutritionally balanced diet for

their babies.

0055 Certain vitamins and minerals may be added to

weaning foods, either to fortify the foods and thus

help insure that an infant’s nutrients intakes are

adequate, or to restore losses which occur during

processing. Manufacturers take professional advice

when deciding on the levels of vitamins or minerals

to add. There is also legislation within the EU setting

down the maximum levels which may be present in

foods intended for infants and young children where

vitamins and minerals are added.

0056 With regard to pesticide residues, EU legislation is

more strict for weaning foods than for foods intended

for older children and adults. Foods intended for

infants and young children may not contain pesticide

residues greater than 0.01 mg kg

1

, which in practice

is the minimum detectable level.

0057 The labels of commercial baby foods provide infor-

mation on the ingredients, nutrient composition, and

suitability for certain special diets. Nutrition infor-

mation is given per 100 g for energy, protein, fat,

and carbohydrate, although many companies also

given information on the sugars, saturates, fiber, and

sodium contents and provide data per serving as well

as per 100 g.

Methods of Preparation

Commercially Made Weaning Foods

0058Commercially made weaning foods are produced by a

variety of methods, some of which are described

below.

0059Cereal-based foods For cereal-based foods, all the

ingredients are mixed together with water to produce

a liquid paste which is pregelatinized and dried using

a roller drier. The dried flakes are then milled to the

required particle size and the product then packed.

0060When using baby rice or other baby cereals at

home, one teaspoon of the cereal should be measured

into a clean bowl and mixed with one tablespoon of

the infant’s usual milk. The amount can be increased

as necessary.

0061For baked cereal-based foods, such as rusks, fat

and water are added to the dry ingredients and

mixed to form a dough. This is converted into a

continuous sheet or ribbon which is then cut, shaped

and baked in a traveling-band oven, and the product

then packed.

0062When using rusks at home, the back of a spoon

should be used to crush a small piece of rusk in a bowl

and then mixed with the infant’s usual milk, or cooled

previously boiled water, to a creamy consistency.

0063Dried foods For other dried weaning foods, dried

ingredients are blended, mixed with water, and

cooked on a roller drier to produce flakes. These are

reduced to the required particle size and then packed.

0064When using dried weaning foods at home, the re-

quired amount of food should be measured into a

clean bowl with a dry spoon. The feeding table pre-

sented on the pack should be used as a guide on the

quantities to offer. The required amount of warm,

previously boiled water should then be added and

mixed thoroughly. For some foods intended for

older infants, it may be necessary to add hot water

to rehydrate the food. If so, then the food must be left

to cool before feeding to the infant.

0065Foods in cans and jars Ready-to-feed weaning foods

in cans and jars are produced as follows. Ingredients

are prepared and weighed, then mixed with water.

Starches, when used, are premixed with water to

insure complete dispersion before addition to the

main batch. Cooking of the mixture is effected via a

steam jacket surrounding the cooking vessel, or via

direct steam injection of the mixture. The cooked

INFANT FOODS/Weaning Foods 3279