The role of weaning in the development of allergies

What causes allergies?
An allergy is an adverse reaction involving the immune system to a protein or pollen that is usually harmless to the general population. In simplistic terms, the body`s immune system reacts to allergens by triggering the release of inflammation-causing histamine from cells in our skin, lungs, nose or intestine. Allergic symptoms include itchy skin, tissue swelling, wheezing, anaphylaxis, conjunctivitis, and gut disturbances. The reasons for the development of allergies in an individual are poorly understood. Researchers continue to investigate the complex interactions between genetic factors, exposure to allergens, pollution and infections.

Possible ways to reduce the risk of developing allergies?
Allergies commonly first occur in infancy or early childhood, and often progress from one allergic symptom to another throughout life – for example from food allergies and eczema in early childhood, to asthma in later childhood, to hay fever in young adulthood. This is known as the allergic march, and research is being carried out to try to find ways of halting this march or indeed to prevent allergies occurring in the first instance. Unfortunately more research is needed before any concrete conclusions can be drawn.

Exclusive breastfeeding from birth and avoidance of tobacco smoke in pregnancy and childhood are widely accepted to be sensible precautions to lower the risk of allergy in a child, as well as having many other health benefits. But what about the weaning diet? Can the timing of giving a child their first solids, and what solids they are given have an impact on their long-term immune health?

Is weaning linked to the development of allergies?
At birth the gut is not fully mature. In the first year of life, exposure to the environment and oral nutrition, particularly immunological factors in breastmilk, play an important role in promoting the maturation of the gut and immune system, particularly immune system elements in the gut mucosa.

Later in the infant`s first year, the introduction of solid foods and of formula milk is a significant event for the immune system in a number of ways:

• The infant is exposed to new food proteins - to which the immune system must become tolerant.
• Nutrients and other factors in foods affect the development of the immune system and immune responses.
• Food choices influence the complex composition of the intestinal flora, which in turn affect immune maturation and responses.

It is entirely possible, therefore, that nutrition early in life might affect the immune system in later life - the ability of the immune system to respond to infections, as well as the ability to down-regulate responses to non-harmful or beneficial antigens (such as proteins in foods).

Commencing weaning – the WHO and UK recommendations
In 2000, the World Health Organisation (WHO) commissioned a systematic review of the evidence of the optimal duration of exclusive breastfeeding², and as a result issued guidance that it should continue for the first six months of life. The revised guidance was adopted in the UK by the Department of Health (DH) from 2003³ - with six months as the recommended age for introducing solid foods to both formula and breastfed infants – a modification of the previous long-standing recommendation of four to six months⁴.

Commencing weaning – what actually happens in the UK?
The recently published 2005 UK Infant Feeding Survey⁵, showed that in fact only a negligible number of parents wait until six months to wean their child to solids, and only 49% wait until the previously recommended 17 weeks (4 months).

The trend from the previous survey of 2000 (as shown in Figure 1) is that the proportion of parents weaning before 17 weeks is significantly decreasing, but this still leaves a huge discrepancy between the government recommendations and current practice. Those shifting to later weaning tend to be mothers from higher social classes, and those with higher educational levels. The survey identified common influences on delaying the age of weaning to be professional advice from Health Visitors, and professional written sources, whereas advice from friends and family more commonly influenced the decision to wean early. The Paediatric Specialist Group of dietitians from the British Dietetic Association (BDA)⁶ recognise the discrepancy between the WHO guidance and current weaning practices in the UK and advise that although breastfeeding can provide complete nutrition for the first 6 months for most infants, there are some infants who may experience faltering growth or nutrient deficiencies unless weaning onto solids is started before this. They recommend for parents who wish to or need to wean their baby before six months of age that 17 weeks should be regarded as the earliest age to start solids, but that a parent`s decision should always be supported by their health professionals accordingly⁶.

Why does timing of weaning matter?
Introduction of solid foods from six months is recognised as essential to meet nutritional needs at this time of rapid growth. Up until six months, the evidence (from the WHO systematic review²) is that breastmilk is sufficient for an infant to thrive - for the majority of healthy, term infants from healthy, well nourished mothers. Formula milk is also adequate as the sole source of nutrition until this age. Around six months of age, stores of nutrients which were laid down during foetal development, such as iron, run low, and therefore supplementary nutrition in the form of solids needs to be started. The introduction of solids from six months also plays an important role in aiding development of the mechanical processes of chewing, controlling foods in the mouth, and these processes aid development of speech muscles. Weaning increases the variety of tastes and flavours and aids integration into family meals. Difficulties in progressing with the stages of weaning - the introduction of lumpy and more solid foods - are more common when weaning is delayed.

What are the risks of early weaning?
A neonate`s gut and kidneys are too immature to cope effectively with solutes and allergens in foods introduced too early. But the definition of too early is not so clear-cut. A systematic review⁷ highlighted the increased risk of eczema when solids are introduced before four months. A prospective birth cohort of 1265 neonates in New Zealand⁸ showed a linear relationship between the number of solid foods introduced before four months and the incidence of eczema by two years old and recurrent chronic eczema by ten years, particularly in infants with parents prone to allergies. The same study did not find a link between early weaning and asthma⁹. More research is needed.

Does the introduction of different allergenic foods need to be delayed?
The consensus in Europe¹⁰ and the US^{11, 12}, is that for at risk infants – i.e. those with a parent or sibling with eczema, asthma, rhinitis, dermatitis or food allergy – weaning should not commence before 17 weeks (ideally not before six months), and no highly allergenic foods should be introduced before six months. Highly allergenic foods by both European and US classification are peanuts, nuts, dairy, egg, wheat, fish and seafood; plus in Europe, sesame seed, mustard seed, soy, celery and sulphites (used as preservatives in some foods and drinks).

Figure 1: Comparison of 2000 and 2005 Infants Feeding Survey findings of age of first introduction of solids

Figure 2: Food mothers avoid giving their 8 to 10 month old child from 2005 Infant Feeding Survey⁵

The joint consensus of the European Society for Paediatric Allergy and Clinical Immunology (ESPACI) and the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN)¹² is that there is no need to delay the introduction of highly allergenic foods beyond six months, however, both the American College of Allergy, Asthma and Immunology¹³ and the American Academy of Paediatrics¹⁴ recommend delaying the introduction of some highly allergenic foods past twelve months – dairy foods after twelve months, egg after 24 months and nuts, fish and seafood after 36 months. These recommendations are a consensus opinion rather than based on solid evidence. The BDA Food Allergy and Intolerance Specialist Group agree with the European consensus – their position statement is that there is no evidence that delaying the introduction of highly allergenic foods beyond six months is beneficial to at risk infants, and there is a published study which indicates it is possible that delayed introduction could adversely affect the development of food allergy¹⁵.

Table 1: Highly allergenic foods – to be avoided before 6 months of age¹⁶

Food	Examples of foods found in7
Peanuts, nuts, sesame seeds, mustard seed	Can be present in chocolate, cakes, breads, nut butters
Dairy	Cows’ milk and mammalian milks other than human breastmilk, yogurt, cream, butter, cheese. Maybe a component of margarines, cakes, breads and many processed foods
Egg	Maybe a component of breads and pastries as glazes
Wheat	Bread, biscuits, pastries, pasta, cous-cous, breakfast cereals. Maybe a component of many processed foods
Fish and seafood	Maybe a component of take-away foods
Soya	Soya milks, yogurts, desserts and cheeses. Maybe a component of many processed food
Celery	Stock or flavouring additive in some processed foods
Sulphite	Preservative used in dried fruit, and many processed and pre-packaged foods and drinks

Do UK mothers delay the introduction of allergenic foods?
The 2005 infant feeding survey⁵ found that 47% of parents of eight- to ten-month-olds were avoiding one or a number of foods from their infant`s diet (different foods shown in Figure 2), 43% of these due to reported food allergy. The same proportion of mothers were avoiding foods in 2000 but the number reporting the reason being due to food allergy was 8% higher in 2005 than 2000. It is unclear from the survey whether this is an indication of an increase in diagnosed allergies or intolerances or reflects an increase in mothers avoiding foods due to perceived reactions, or delayed introduction of foods due to the worry of a potential allergy. Avoiding nutritious foods such as dairy, eggs and wheat, without good reason is inadvisable for a number of reasons – nutritional adequacy of diet progression with the introduction of different flavours and textures is critical at this age, to ensure acceptance of a varied diet if the child is allergic to any of these foods. It is easier to see this if they are introduced at this stage, and then they can be appropriately avoided.

Practical advice for parents For healthy, term infants from well-nourished, healthy mums, delay weaning until as near to six months as possible, and definitely beyond 17 weeks. (For preterms the advice is between five and seven months uncorrected age). For infants with a parent or sibling with a history of allergic disease don`t introduce any highly allergenic foods before six months (see Table 1). For infants with a parent or sibling with a history of allergic disease, highly allergenic foods (see Table 1) can be introduced at any time after six months, but aim to introduce one at a time, starting with a small amount, allowing a few days in between each new food so any allergic reaction is clear. If an infant has an obvious reaction to a food, seek advice from a family doctor or Health Visitor. Referral should be made to a registered Paediatric Dietitian if a major food or food group is to be excluded

NB Throughout this article the term weaning is used to mean the introduction of solid foods into an infant`s diet, to be supplementary to continued breastfeeding or formula feeding. Table 2: Weaning stages, adapted from Weaning and the Weaning diet (DH 1994)4 reflecting current DH guidance

	Stage 17	Stage 2	Stage 3
Age	Ideally six months, but definitely not before 17 weeks	Six to nine months	Nine to twelve months
Textures	Smooth, puréed food such as rice based cereal, fruit or vegetable purée	Mashed, slightly lumpy food such as cooked mashed fruit and vegetables, soft cooked minced or puréed meat, fish or pulses. Finger foods such as hard boiled egg, toast	Food with small soft pieces

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References

1. Gupta R et al. Burden of allergic disease in the UK: secondary analyses of national databases. Clin Exp Allergy (2004); 34(4):520-6
2. Kramer S and Kakuma R. The optimal duration of exclusive breastfeeding: A systematic review. Adv Exp Med Biol (2004); 554: 63-77.
3. Department of Health, Infant Feeding Recommendations (2004) www.dh.gov.uk
4. Department of Health, Weaning and the weaning diet: Report on Health and Social Subjects 45. (1994) HMSO. London
5. Infant Feeding Survey 2005. Accessed online at: www.ic.nhs.uk/statisticsand- data-collections/health-and-lifestyles/infant-feeding/infant-feedingsurvey- 2005 (2007)
6. BDA Paediatric Group. Position Statement on Breastfeeding and Weaning onto Solid Foods www.bda.uk.com (2004)
7. Fergusson DM et al. Early solid feeding and recurrent childhood eczema: a 10-year longitudinal study. Pediatrics (1990); 86: 541-546.
8. Fergusson DM et al. Eczema and infant diet. Clin allergy (1981) 11: 325-331.
9. Fergusson DM et al. Asthma and infant diet. Arch Dis Child (1983); 58:48-51.
10. Host A et al. Dietary Products used in infants for treatment and prevention of food allergy. Joint Statement of the European Society for Paediatric Allergology and Clinical Immunology (ESPACI) Committee on the Hypoallergenic Formulas and the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) Committee on Nutrition. Arch Dis Child (1999); 81:80-84
11. Fiocchi A et al. Food Allergy and the introduction of solid foods to infants: a consensus document. Adverse Reactions to Foods Committee, American College of Allergy, Asthma and immunology. Ann Allergy Asthma Immunol (2006); 97(1) 10-20
12. American Academy of Pediatrics, Committee on Nutrition. Hypoallergenic Infant Formulas. Pediatrics (2000); 106:346-349
13. Zeiger RS. Food Allergen Avoidance in the Prevention of Food Allergy in Infants and Children, Pediatrics (2003); 111(6):1662-1671
14. BDA Food Allergy and Intolerance Specialist Group. Professional consensus statement - Practical dietary prevention strategies for infants at risk of developing allergic diseases. www.bda.uk.com (members site only) (2005)
15. Zutavern A et al. The introduction of solids in relation to asthma and eczema. Arch Dis Child (2004); 89:303-8