New guidelines explained by Janice Joneja Ph.D, RD
One of the most significant changes in paediatric food allergy management in recent years has been in strategies to prevent food allergy in early infancy. Previously the idea prevailed that if the most highly allergenic foods are withheld from the infant until the immune and digestive systems are more mature, allergic sensitization would be prevented or significantly reduced. Frequently the advice regarding introduction of the most highly allergenic foods was, “the later the better”. It was hoped that this would in turn prevent not only allergy to food but to inhalant and contact allergies in later life. However, new research seems to indicate the very opposite – that exposureto allergens in early life may actually tolerise the infant’s immune system, and prevent allergic sensitization to food1.
The potential to develop allergy is inheritance of a specific immunological response to allergens2, not inheritance of allergy to a specific allergen. Allergic sensitization depends on the baby’s exposure to the allergen and the response of his or her immune system at the time of exposure, although some foods are more likely than others to lead to allergy.
Food Allergy and Other Allergic Diseases
For many years it was assumed that if the early onset of allergy could be prevented or delayed, the child might avoid what allergists like to call the “allergic march” – the progression from food allergy to inhalant-triggered respiratory allergy and asthma which usually have their onset at a later age. It was assumed that the early expression of allergy in the form of allergic reaction to foods “primed” the immune system to take the “atopic route” and, once started, like a train starting from a station and accelerating along its track, the response would progress to respiratory allergy and asthma. However, newer research has demonstrated that this is not necessarily the case. Prevention of food allergy in early infancy prevents or reduces food allergy; the direct effect of food allergy in the development of allergy to airborne and environmental allergens has yet to be identified by scientific studies.
Nevertheless, it is extremely important to prevent, reduce, or relieve food allergy as early as possible because of the central role of allergy to foods in many allergic diseases (particularly eczema), its contribution to asthma and allergic rhinitis, and the real danger of life-threatening anaphylactic reactions.
Does Atopic Disease Start in Foetal Life?
Food allergens can be detected in amniotic fluid, indicating that allergenic material to which the mother has been exposed can cross the placenta3. However, there is no real evidence to suggest that the foetal immune system will respond to these allergens4. In fact some authorities suggest that exposure to food antigens in utero may promote foetal tolerance5, that is, the immune system is “educated” to recognize the food as “foreign but safe” and not to mount a defensive action against it when the food is encountered at any time in the future. So, exposure to food molecules may mark the beginning of our ability to consume food with impunity.
There is no evidence to suggest that maternal avoidance of any foods other than her own allergens (to reduce her own allergic response) during pregnancy will improve the allergic status of her baby. A 1988 report6 indicated that excluding highly allergenic foods from the mother’s diet during pregnancy did not affect the atopic status of the infant in any way, and evidence from research studies thereafter supports this finding. In contrast to earlier thinking, this means that there is no reason for mother to exclude foods to which the baby’s father is allergic.
Breast-feeding and Allergy
Breast milk provides the ideal nutritional, immunologic and physiologic nourishment for all newborns. Components of human milk enhance the baby’s natural defences and promote maturation of the immune system7. In view of the large amount of evidence regarding the role of breast milk in promoting the well-being of all babies, based on careful analysis of all research data on the topic, European and American academic groups (ESPACI and ESPGHANand AAP8, 9) strongly recommend exclusive breast-feeding for 4-6 months with introduction of complementary foods10 no earlier than 4-6 months as the hallmark for allergy prevention 7, 11.
The current directives from position papers and consensus documents from many countries now recognize that restriction of the maternal diet during pregnancy and lactation is contraindicated in allergy prevention7,12,13
In summary, professional groups do not recommend the elimination of any specific foods from the maternal diet during breast-feeding except for the mother’s own allergens unless the baby has been diagnosed with allergy to one or more foods, in which case the baby’s allergenic food should be avoided by its mother as long as she is breast-feeding.
It is not always possible for a baby to be breast-fed, and when the infant is at risk for, or has developed allergies, making the best choice of formula is extremely important.
Most authorities suggest that if a baby has no signs or symptoms of cow’s milk allergy, a conventional cow’s milk-based formula is safe for infant feeding.
However, in ‘high risk for allergy’ babies, there is emerging evidence that hydrolyzed infant formulas provide a measure of protection against the development of atopic disease14 compared to conventional milk-based formulas. Hydrolysis of cow’s milk breaks the protein into smaller, potentially less allergenic proteins.
Based on the evidence from a variety of studies15,16,17 the American Academy of Pediatrics in their position paper published in 20087 states that, “In studies of infants at high risk of developing atopic disease who are not breast-fed exclusively for 4 to 6 months or are formula fed, there is modest evidence that atopic dermatitis may be delayed or prevented by the use of extensively hydrolyzed or partially hydrolyzed formulas, compared with cow’s milk formula, in early childhood.” They further stated that, “Extensively hydrolyzed formulas may be more effective than partially hydrolyzed in the prevention of atopic disease”.
There is good consensus amongst paediatric groups world-wide that there is no evidence for the use of soy-based infant formula for the purpose of allergy prevention7, 8,18
Introducing Solid Foods
The first consensus document on the introduction of solid foods for the food-allergic infant was published in July 2006 by the Adverse Reactions to Foods Committee of the AmericanCollegeof Allergy, Asthma and Immunology19. They recommended that introduction of the multiple allergens in solid foods to the allergic infant is preferably delayed until after six months of age. Until this age the authors suggest that the infant’s immature digestive tract and immune system may increase the risk of sensitization and development of allergy. Furthermore, it was recommended that the most highly allergenic foods should not be introduced until after one year of age or later. Specific times of introduction were suggested as: cow’s milk at 12 months; egg at 24 months; peanut, tree nut and fish at three years. Most Western countries, including the UK, followed these recommendations.
However, more recent research has demonstrated that these recommendations were neither supported by evidence-based research nor were they effective in practice. Newer position papers reflect this change in approach. The AAP paper, published in 20087 states, “..the evidence…does not allow one to conclude that there is a strong relationship between the timing of the introduction of complementary foods and development of atopic disease”.
According to the current published guidelines of all paediatric societies and consensus committees, solid foods should be introduced individually and gradually, starting at about four to six months of age. Each food should be introduced, ideally over a four-day period, with careful monitoring of the baby for the development of signs of allergy. Some studies suggest that foods, especially gluten-containing grains, should be introduced at about six months of age while breast-feeding for optimum tolerance development20. Early introduction (e.g. before one year of age) of even highly allergenic foods such as peanut is likely to lead to tolerance rather than sensitisation21.
There is no evidence to suggest that any food should be delayed after six months of age, nor guidelines to suggest any particular order of introduction of solid foods. No mixed foods should be given until each food in the mixture has been given to the baby and is tolerated. Current research is indicating that there may be a “window of opportunity” when the child’s immune system is most likely to tolerate the food, and that if this is missed there may be an increased likelihood of sensitization. Future research will undoubtedly reveal the ideal times for introduction of specific foods.
SUMMARY OF DIETARY GUIDELINES FOR THE ‘HIGH RISK FOR ALLERGY’ BABY DURING PREGNANCY, LACTATION, AND EARLY INFANT FEEDING:
A high risk for allergy is defined as a baby with one first degree relative (parent or sibling) with a diagnosed allergy
There should be no dietary restriction during pregnancy except:
o Mother must avoid her own allergenic foods to avoid any allergic reactions
It is essential that mother should obtain complete balanced nutrition appropriate for pregnancy, and eat as wide a range of foods as possible
The allergic mother must ensure that she is consuming equivalent nutrients in the alternative foods she is eating as substitutes for her allergens
Mother should not restrict her own diet while breast-feeding except:
Mother must avoid her own allergenic foods
o Mother must avoid any foods to which her baby has been diagnosed as allergic
Exclusive breast-feeding should be continued for 4 – 6 months.
For the breast-fed baby the introduction of solid foods or infant formula (complementary foods) should be delayed until at least 4-6 moths
If breast-feeding is not possible, hydrolyzed infant formula can be used as a measure to prevent food allergy. Extensively hydrolyzed formulas are thought to be more effective than partially hydrolyzed formulas in allergy prevention
Soy-based formulae and other milk-based formulas (e.g. goat’s milk) are not recommended for reducing the risk of food allergy
If the child is allergic to cow’s milk, extensively hydrolyzed casein based formulae or amino acid based formulae should be used if breast-feeding is not possible
If the baby is not allergic to cow’s milk, a normal cow’s milk formula can be introduced as complementary food at 4-6 months
There is no benefit in delaying the introduction of solid foods beyond 6 months of age
There are no recommendations regarding the sequence in which complementary foods are introduced. Even highly allergenic foods can be introduced early (e.g. before 1 year) in order to maximise the development of tolerance
Each food should be introduced separately and mixed foods introduced only after each food in the mixture has been introduced and tolerated
© Janice M. Joneja, Ph.D., RD, Website: www.allergynutrition.com
Dr Janice Joneja, patron of AAA, has 30 years’ experience as a clinical counsellor in the area of biochemical and immunological reactions involved in food allergy and intolerance. Born and growing up in England, her home is now in Canada, where for 12 years she was head of the Allergy Nutrition Programme at the Vancouver Hospital and Health Sciences Centre. She lectures at universities, colleges and hospitals internationally and her books are highly respected manuals providing practical guidance for both the professional and lay reader. She has undertaken UKseminars on food allergy diagnosis and treatment, on behalf of AAA.
1 Allergic sensitization involves an immunological response to the allergen with the production of allergen-specific IgE;
Immunological tolerance indicates that consumption of the allergenic food does not result in an allergic response.
10 Complementary foods include infant formulae and solid foods.
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This article was first published in Allergy Newsletter No. 102, Summer 2011.