- Email: [email protected]
Beyond breast-feeding
Beyond breast-feeding Patterns of breast-feeding have changed radically in the last few decades, particularly in affluent countries. In these countries rates of breast-feeding became particularly low in the 1960s and 1970s, when only 20% of babies were still being breast-fed at 3 months of age. Finding reasons to explain any changes in behavior is always difficult, but in the case of this sharp decrease in the percent of babies being breast-fed several factors may have been influential. First, the number of women in the workforce, especially women of childbearing age, increased dramatically during the same period. Although this has had indisputable social benefits, it has been at least partly responsible for the reduced prevalence of breast-feeding. It is a major concern that downward trends have also occurred in developing countries, especially in urban regions.1 In all countries these trends have been accompanied by more readily available infant feeding formulas that have become safer and more marketable as manufacturers continue to make greater efforts to emulate the nutrition provided by breast milk. Although rates of breast-feeding in affluent countries in the last 2 decades have slowly risen back to the levels that they were in the 1950s, the rates still remain less than optimal in many places. It is difficult to make between-country comparisons because definitions and study methods vary widely. However, recent surveys suggest that 60% of babies are breast-fed at age 3 months and 20% at 6 months in the United States,2,3 only 25% of babies are breast-fed at 4 months in the United Kingdom, and 58% of babies are breast-fed at age 4 months in Australia. It is interesting that rates in the Netherlands, Denmark, Sweden, and Norway are much higher, with up to 80% of babies being breast-fed at age 3 months.4 This suggests that a further increase could be attained in other affluent countries if sufficient resources were invested in public health programs. With increasing recognition that formula feeding increases the risk of morbidity from many illnesses both in the short term and the long term,5 it is encouraging that the role of breast-feeding has begun to receive the attention from health professionals that it deserves. Since the early 1980s, the promotion and support of breast-feeding has been the focus of many international governmental
From the Clinical Epidemiology Unit and the James Fairfax Institute of Paediatric Nutrition, Department of Paediatrics and Child Health, University of Sydney, New Children’s Hospital, Westmead, and the TVW Telethon Institute for Child Health Research, West Perth, Australia. Received for publication June 1, 1999; revised June 4, 1999; accepted for publication June 4, 1999. Reprint requests: Jennifer K. Peat, PhD, New Children’s Hospital, PO Box 3515, Parramatta, NSW, Australia. J Allergy Clin Immunol 1999;104:526-9. Copyright © 1999 by Mosby, Inc. 0091-6749/99 $8.00 + 0 1/1/100874
526
and nongovernmental organizations. In particular, World Health Organization initiatives have been instrumental in promoting breast-feeding and in preventing the erosion of traditional breast-feeding practices in developing countries. In the United States, the surgeon general has made increasing the incidence of breast-feeding an objective of Healthy People 2000, and, as a result, some hospitals have established successful breast-feeding promotion projects.3 Breast-feeding is important for the health of babies because breast milk compensates for babies’ immature immune systems by providing an active transfer system of maternal antibodies and by providing IgA antibodies and other defense factors.6,7 Thus breast-feeding provides health benefits for all infants but especially in developing countries where the use of formula feeding in early life confers particular health risks. The antibodies in breast milk are important because they are directed against the bacterial, fungal, viral, and other antigenic substances to which the mother has been recently exposed. The active components in human milk include lactoferrin that suppresses cytokine production and thereby has an anti-inflammatory action, lysozyme that attacks the walls of gram-positive bacteria, oligosaccha-
J ALLERGY CLIN IMMUNOL VOLUME 104, NUMBER 3, PART 1
rides that prevent binding of toxins to receptors and to epithelial cells in the infant’s airway walls, and lipids that have an antimicrobial action. Breast milk also contains a number of growth factors and cytokines that contribute to the maturation of the immune system. It is thought that these protective components are directly responsible for reducing the incidence of many illnesses that are an important source of morbidity in infancy, including acute diarrhea, lower respiratory tract infections, and otitis media.8-11 In addition, there is evidence that breast-feeding protects against more serious conditions such as necrotizing enterocolitis, bacterial meningitis, botulism, urinary tract infections, and sudden infant death syndrome and, in the longer term, protects against insulin-dependent diabetes mellitus, inflammatory bowel disease, and childhood lymphoma.2,12 One of the major benefits of exclusive breast-feeding appears to be protection against the development of allergic symptoms. In this issue of the Journal, Wright et al (p •••) provide exciting new evidence of the positive longterm health outcomes for children associated with breastfeeding beyond age 4 months. In one of the very few studies of the long term-health effects of modes of infant feeding, these researchers were able to examine the effect of breast-feeding on trends in the development of IgE in a large birth cohort of children studied until they were 11 years old. The study reports that children who were breast-fed for more than 3 months had significantly lower serum IgE levels at both 6 and 11 years old if their mothers were in the 2 lower tertiles of serum IgE levels, after adjustment for other confounders. Serum IgE levels in breast-fed children were approximately 1.7 times lower than in non-breast-fed children at both ages 6 and 11 years. This new information from Wright et al supports prior evidence from the Tucson research group and from other research groups that there is a protective relationship between breast-feeding and the development of allergy,13 allergic symptoms,14 wheezing illness,15,16 and asthma.17-20 As such, this study is an important further step toward resolving what some health professionals still see as a controversy. The study reported in the Journal is particularly innovative in that comprehensive data collected prospectively over many years have allowed the researchers to explore interactions with another important risk factor for childhood asthma, that is, levels of maternal IgE. The findings of this study are important for two reasons. First, the study demonstrates a long-term sustainable effect of breast-feeding on the reduction of allergic sensitization. The long-term effect on allergy and allergic symptoms has previously only been demonstrated in cohorts studied to less than age 8 years9,13,17,19 and in one longer-term study to age 17 years.14 Second, there is strong evidence from our own epidemiologic studies that the severity of asthmatic symptoms in children is strongly related to IgE levels and that children who become atopic at an early age are at much greater risk for development of clinically important asthma in later years.21
Peat, Allen, and Oddy 527
Put together, this evidence strongly implies that any methods that contribute to the maintenance of low IgE levels in early life, such as interventions to increase rates of prolonged breast-feeding, are likely to result in an overall down-regulation of asthma morbidity in later life. Interestingly, in the study of Wright et al levels of breast-feeding and serum IgE were not related in children of mothers who were in the highest tertile of serum IgE levels. As Wright et al point out, it is possible that some aspect of the shared environment of susceptible mothers and their children, such as high allergen exposure levels or a common predisposition to produce IgE in response to allergen exposure, might swamp the beneficial effects of breast-feeding. This seems quite likely because the magnitude of the effects of allergen exposure on the risk of sensitized children developing asthma are much greater than any effects that have been recorded for a lack of breast-feeding. Studies that have quantified the relative effects of these factors show that the odds ratios for development of asthma in sensitized children exposed to the relevant allergens range between 2 and 20. However, the odds ratio for children to have asthma if they are not breast-fed for at least 3 months is much smaller at approximately 1.5-2.0.22 Another possible explanation for the lack of association between breast-feeding and IgE in children of highly allergic mothers may be that mothers with high serum IgE levels may produce breast milk with a different composition from that of nonallergic mothers. There is some evidence that omega-3 fatty acid levels in breast milk are higher in nonallergic mothers.23 Because omega-3 fatty acids confer a protection against the development of cellular inflammation, this may have contributed to the association found by Wright et al. It is important to note that only a minority, that is, 16%, of mothers in the study of Wright et al were in the high IgE range and that the overlap of the confidence intervals around the levels of IgE in children of high- or low-allergic mothers shown in the tables does not suggest that breast-feeding confers any disadvantage. It is also important to note that the difference between groups in the figure has been exaggerated by the nonlogarithmic presentation of IgE levels that have an established log-normal distribution. However, this small methodologic consideration should not detract from the important findings of this study. Although the overall evidence for the long-term effects of breast-feeding are now particularly well documented and the evidence that breast-feeding may have a role in disease prevention is now consistent across many study types, the subgroups of children who might benefit most are still not well defined. We would hypothesize that infants at high risk for development of asthma because of a family history of allergic illness are very likely to have allergic symptoms of some type but these symptoms will be less severe if the infants are breast-fed in the first few months of life. For this reason, it is important that further evidence is collected of the effects of avoiding formula feeding in this high-risk group and also of the influence of maternal diet, which, if modulated,
528 Peat, Allen, and Oddy
may prevent any transfer of allergenic food derivatives to the infant. Previous studies suggest that breast-feeding is especially important in preventing the onset of allergic illness for male children, certain ethnic groups, children who share a room,10 and babies of mothers who smoke.8 It is important to keep this particular evidence in perspective and to remember that it is only clinically relevant from a mechanistic viewpoint and not from a public health perspective. The multitude of potential health and psychologic benefits that breast-feeding confers both to the infant and to the mother–infant relationship confirms that effective promotional strategies need to be directed at the entire community to optimize the health of all babies. In trying to establish a relationship between breastfeeding and allergic disease, the inherent problems of epidemiologic studies for which there are few reliable methods with which to measure exposures to different infant feeding modes have been frustrating. The lack of reliable methods has meant that consistent evidence of the relationship between breast-feeding and allergic disease that health professionals find convincing has taken more than a decade to assemble. An added complication has been that breast-feeding does not end the day that formula feeding is introduced. Rather, there is gradual change over the weaning period that may last between 1 week to several months. Thus it is has been impossible to disentangle the risk conferred by formula feeding from the protection afforded by breast-feeding. Also, because there is strong collinearity between measurements of babies ever being breast-fed and being exclusively breast-fed, their effects could only be separated out in studies with extremely large sample sizes. Because this will never be feasible in cohort studies in which sample size is necessarily limited and very large resources are needed to maintain high follow-up rates over a long period, it will be extremely difficult to collect evidence for the long-term independent effects of exclusive breastfeeding and partial formula feeding. Nevertheless, breast-feeding seems to be one of those rare etiologic factors that has biologically plausible effects for which there is consistent evidence that is potentially open to public health promotions and for which there is now substantial evidence of its influence on the subsequent health of children. From a public health perspective, it has become important to convince mothers to consider the health effects for their children that last for a long time beyond the period of breast-feeding. To achieve this, breast-feeding will need to be widely promoted and strategies put in place to support all women who choose to breast-feed, including those who return to work. In the home, support services may include ready access to professionals with expertise in infant feeding practices. In the workplace, supportive strategies may include the provision of facilities for feeding or expressing, flexible work options, and acceptance from colleagues. In the general community, active education through local health care agencies to promote the benefits of breast-feeding and to reduce opposition to
J ALLERGY CLIN IMMUNOL SEPTEMBER 1999
breast-feeding in public places will be needed. In addition, government initiatives to provide adequate maternity leave in all workplaces will facilitate breast-feeding by helping to ensure that mothers have prolonged personal contact with their babies. From a public health perspective, it would seem important that all babies receive breast milk for as long as possible. Early evidence from research studies10,24 and a recent systematic review25 shows that communitybased trials of breast-feeding promotion and extra support from professionals with special skills in early infant feeding are effective in prolonging breast-feeding. Because breast-feeding rates remain less than optimal in many countries, public health strategies to further promote the beneficial effects of breast-feeding, to prevent babies from unnecessary early exposure to formula feeding, and to support all mothers who choose to breast-feed are urgently required. Health goals to increase breastfeeding rates at least to those of Scandinavian countries would not seem unreasonable. The increasing evidence that exclusive breast-feeding plays an important role in the prevention of systemic and allergic illnesses throughout childhood suggests that any public health strategies that increase the prevalence and the duration of breast-feeding will provide many important health benefits for future generations of children. One of the health benefits will be the down-regulation of allergic sensitization and the subsequent prevention of the onset of allergic and asthmatic symptoms in later childhood. Jennifer K. Peat, PhD Clinical Epidemiology Unit PO Box 3515 Parramatta, NSW, Australia Jane Allen, PhD James Fairfax Institute of Paediatrics University of Sydney New Children’s Hospital Westmead, Australia Wendy Oddy, MPH TVW Telethon Institute for Child Health Research West Perth, Australia REFERENCES 1. Grummer-Strawn LM. The effect of changes in population characteristics on breastfeeding trends in fifteen developing countries. Int J Epidemiol 1996;25:94-102. 2. Heinig MJ, Dewey KG. Health advantages of breast feeding for infants: a critical review. Nutrition Res Rev 1996;9:89-110. 3. Raisler J, Alexander C, O’Campo P. Breast-feeding and infant illness: a dose-response relationship? Am J Public Health 1999;89:25-30. 4. Hunter HH. Why many more women breastfeed in Norway than in Britain. New Generation J NCT 1996;15:26-7. 5. Cunningham AS, Jelliffe DB, Jelliffe EFP. Breast-feeding and health in the 1980s: a global epidemiologic review. J Pediatr 1991;118:659-66. 6. Wold AE, Adlerberth I. Does breastfeeding alter the infant’s immune responsiveness? Acta Paediatr 1998;87:19-22. 7. Hanson LA, Hahn-Zoric M, Berndes M, Ashraf R, Herias V, Jalil F, et al. Breast feeding: overview and breast milk immunology. Acta Paediatrica Jpn 1994;36:557-61. 8. Nafstad P, Jaakkola JJK, Hagen JA, Botten G, Kongerud J. Breastfeeding, maternal smoking and lower respiratory infections. Eur Respir J 1996;9:2623-9.
J ALLERGY CLIN IMMUNOL VOLUME 104, NUMBER 3, PART 1
9. Wilson AC, Forsyth JS, Greene SA, Irvine L, Hau C, Howie PW. Relation of infant diet to childhood health: seven year follow up of cohort of children in Dundee infant feeding study. BMJ 1998;316:21-5. 10. Wright AL, Bauer M, Naylor A, Sutcliffe E, Clark L. Increasing breastfeeding rates to reduce infant illness at the community level. Pediatrics 1998;101:837-44. 11. Duncan B, Ey J, Holberg CJ, Wright AL, Martinez FD, Taussig LM. Exclusive breast-feeding for at least 4 months protects against otitis media. Pediatrics 1993;91:867-72. 12. Wold AE, Hanson LA. Defense factors in human milk. Curr Opin Gastroenterol 1994;20:652-8. 13. Chandra RK, Singh G, Shridhara B. Effect of feeding whey hydrolysate, soy and conventional cow milk formulas on incidence of atopic disease in high risk infants. Ann Allergy 1989;63:102-6. 14. Saarinen UM, Kajosaari M. Breastfeeding as prophylaxis against atopic disease: prospective follow-up study until 17 years old. Lancet 1995;346:1065-9. 15. Wright AL, Holberg CJ, Martinez FD, Morgan WJ, Taussig LM, Group Health Associates. Breast feeding and lower respiratory tract illness in the first year of life. BMJ 1989;299:946-9. 16. Wright AL, Holberg CJ, Taussig LM, Martinez FD. Relationship of infant feeding to recurrent wheezing at age 6 years. Arch Pediatr Adolesc Med 1995;149:758-63. 17. Burr ML, Limb ES, Maguire MJ, Amarah L, Eldridge BA, Layzell JCM, et al. Infant feeding, wheezing, and allergy: a prospective study. Arch Pediatr Adolesc Med 1993;68:724-8.
Peat, Allen, and Oddy 529
18. Infante-Rivard C. Childhood asthma and indoor environmental risk factors. Am J Epidemiol 1993;137:834-44. 19. Tariq SM, Matthews SM, Hakim EA, Stevens M, Arshad SH, Hide DW. The prevalence of and risk factors for atopy in early childhood: a whole population birth cohort study. J Allergy Clin Immunol 1998;101:587-93. 20. Rylander E, Pershagen G, Eriksson M, Nordvall L. Parental smoking and other risk factors for wheezing bronchitis in children. Eur J Epidemiol 1993;9:517-26. 21. Peat JK, Salome CM, Woolcock AJ. Longitudinal changes in atopy during a 4-year period: relation to bronchial hyperresponsiveness and respiratory symptoms in a population sample of Australian schoolchildren. J Allergy Clin Immunol 1990;85:65-74. 22. Peat JK, Li J. Reversing the trend: reducing the prevalence of asthma. J Allergy Clin Immunol 1999;103:1-10. 23. Yu G, Duchen K, Bjorksten B. Fatty acid composition in colostrum and mature milk from non-atopic and atopic mothers during the first 6 months of lactation. Acta Pediatr 1998;87:729-36. 24. Morrow AL, Guerrero ML, Shults J, Calva JJ, Lutter C, Bravo J, et al. Efficacy of home-based peer counselling to promote exclusive breastfeeding: a randomised controlled trial. Lancet 1999;353:1226-31. 25. Sikorski J, Renfrew MJ. Support for breastfeeding mothers. [Cochrane Review]. In: The Cochrane Library, Issue 1. Oxford: Update Software; 1999.
From the Clinical Epidemiology Unit and the James Fairfax Institute of Paediatric Nutrition, Department of Paediatrics and Child Health, University of Sydney, New Children’s Hospital, Westmead, and the TVW Telethon Institute for Child Health Research, West Perth, Australia. Received for publication June 1, 1999; revised June 4, 1999; accepted for publication June 4, 1999. Reprint requests: Jennifer K. Peat, PhD, New Children’s Hospital, PO Box 3515, Parramatta, NSW, Australia. J Allergy Clin Immunol 1999;104:526-9. Copyright © 1999 by Mosby, Inc. 0091-6749/99 $8.00 + 0 1/1/100874
526
and nongovernmental organizations. In particular, World Health Organization initiatives have been instrumental in promoting breast-feeding and in preventing the erosion of traditional breast-feeding practices in developing countries. In the United States, the surgeon general has made increasing the incidence of breast-feeding an objective of Healthy People 2000, and, as a result, some hospitals have established successful breast-feeding promotion projects.3 Breast-feeding is important for the health of babies because breast milk compensates for babies’ immature immune systems by providing an active transfer system of maternal antibodies and by providing IgA antibodies and other defense factors.6,7 Thus breast-feeding provides health benefits for all infants but especially in developing countries where the use of formula feeding in early life confers particular health risks. The antibodies in breast milk are important because they are directed against the bacterial, fungal, viral, and other antigenic substances to which the mother has been recently exposed. The active components in human milk include lactoferrin that suppresses cytokine production and thereby has an anti-inflammatory action, lysozyme that attacks the walls of gram-positive bacteria, oligosaccha-
J ALLERGY CLIN IMMUNOL VOLUME 104, NUMBER 3, PART 1
rides that prevent binding of toxins to receptors and to epithelial cells in the infant’s airway walls, and lipids that have an antimicrobial action. Breast milk also contains a number of growth factors and cytokines that contribute to the maturation of the immune system. It is thought that these protective components are directly responsible for reducing the incidence of many illnesses that are an important source of morbidity in infancy, including acute diarrhea, lower respiratory tract infections, and otitis media.8-11 In addition, there is evidence that breast-feeding protects against more serious conditions such as necrotizing enterocolitis, bacterial meningitis, botulism, urinary tract infections, and sudden infant death syndrome and, in the longer term, protects against insulin-dependent diabetes mellitus, inflammatory bowel disease, and childhood lymphoma.2,12 One of the major benefits of exclusive breast-feeding appears to be protection against the development of allergic symptoms. In this issue of the Journal, Wright et al (p •••) provide exciting new evidence of the positive longterm health outcomes for children associated with breastfeeding beyond age 4 months. In one of the very few studies of the long term-health effects of modes of infant feeding, these researchers were able to examine the effect of breast-feeding on trends in the development of IgE in a large birth cohort of children studied until they were 11 years old. The study reports that children who were breast-fed for more than 3 months had significantly lower serum IgE levels at both 6 and 11 years old if their mothers were in the 2 lower tertiles of serum IgE levels, after adjustment for other confounders. Serum IgE levels in breast-fed children were approximately 1.7 times lower than in non-breast-fed children at both ages 6 and 11 years. This new information from Wright et al supports prior evidence from the Tucson research group and from other research groups that there is a protective relationship between breast-feeding and the development of allergy,13 allergic symptoms,14 wheezing illness,15,16 and asthma.17-20 As such, this study is an important further step toward resolving what some health professionals still see as a controversy. The study reported in the Journal is particularly innovative in that comprehensive data collected prospectively over many years have allowed the researchers to explore interactions with another important risk factor for childhood asthma, that is, levels of maternal IgE. The findings of this study are important for two reasons. First, the study demonstrates a long-term sustainable effect of breast-feeding on the reduction of allergic sensitization. The long-term effect on allergy and allergic symptoms has previously only been demonstrated in cohorts studied to less than age 8 years9,13,17,19 and in one longer-term study to age 17 years.14 Second, there is strong evidence from our own epidemiologic studies that the severity of asthmatic symptoms in children is strongly related to IgE levels and that children who become atopic at an early age are at much greater risk for development of clinically important asthma in later years.21
Peat, Allen, and Oddy 527
Put together, this evidence strongly implies that any methods that contribute to the maintenance of low IgE levels in early life, such as interventions to increase rates of prolonged breast-feeding, are likely to result in an overall down-regulation of asthma morbidity in later life. Interestingly, in the study of Wright et al levels of breast-feeding and serum IgE were not related in children of mothers who were in the highest tertile of serum IgE levels. As Wright et al point out, it is possible that some aspect of the shared environment of susceptible mothers and their children, such as high allergen exposure levels or a common predisposition to produce IgE in response to allergen exposure, might swamp the beneficial effects of breast-feeding. This seems quite likely because the magnitude of the effects of allergen exposure on the risk of sensitized children developing asthma are much greater than any effects that have been recorded for a lack of breast-feeding. Studies that have quantified the relative effects of these factors show that the odds ratios for development of asthma in sensitized children exposed to the relevant allergens range between 2 and 20. However, the odds ratio for children to have asthma if they are not breast-fed for at least 3 months is much smaller at approximately 1.5-2.0.22 Another possible explanation for the lack of association between breast-feeding and IgE in children of highly allergic mothers may be that mothers with high serum IgE levels may produce breast milk with a different composition from that of nonallergic mothers. There is some evidence that omega-3 fatty acid levels in breast milk are higher in nonallergic mothers.23 Because omega-3 fatty acids confer a protection against the development of cellular inflammation, this may have contributed to the association found by Wright et al. It is important to note that only a minority, that is, 16%, of mothers in the study of Wright et al were in the high IgE range and that the overlap of the confidence intervals around the levels of IgE in children of high- or low-allergic mothers shown in the tables does not suggest that breast-feeding confers any disadvantage. It is also important to note that the difference between groups in the figure has been exaggerated by the nonlogarithmic presentation of IgE levels that have an established log-normal distribution. However, this small methodologic consideration should not detract from the important findings of this study. Although the overall evidence for the long-term effects of breast-feeding are now particularly well documented and the evidence that breast-feeding may have a role in disease prevention is now consistent across many study types, the subgroups of children who might benefit most are still not well defined. We would hypothesize that infants at high risk for development of asthma because of a family history of allergic illness are very likely to have allergic symptoms of some type but these symptoms will be less severe if the infants are breast-fed in the first few months of life. For this reason, it is important that further evidence is collected of the effects of avoiding formula feeding in this high-risk group and also of the influence of maternal diet, which, if modulated,
528 Peat, Allen, and Oddy
may prevent any transfer of allergenic food derivatives to the infant. Previous studies suggest that breast-feeding is especially important in preventing the onset of allergic illness for male children, certain ethnic groups, children who share a room,10 and babies of mothers who smoke.8 It is important to keep this particular evidence in perspective and to remember that it is only clinically relevant from a mechanistic viewpoint and not from a public health perspective. The multitude of potential health and psychologic benefits that breast-feeding confers both to the infant and to the mother–infant relationship confirms that effective promotional strategies need to be directed at the entire community to optimize the health of all babies. In trying to establish a relationship between breastfeeding and allergic disease, the inherent problems of epidemiologic studies for which there are few reliable methods with which to measure exposures to different infant feeding modes have been frustrating. The lack of reliable methods has meant that consistent evidence of the relationship between breast-feeding and allergic disease that health professionals find convincing has taken more than a decade to assemble. An added complication has been that breast-feeding does not end the day that formula feeding is introduced. Rather, there is gradual change over the weaning period that may last between 1 week to several months. Thus it is has been impossible to disentangle the risk conferred by formula feeding from the protection afforded by breast-feeding. Also, because there is strong collinearity between measurements of babies ever being breast-fed and being exclusively breast-fed, their effects could only be separated out in studies with extremely large sample sizes. Because this will never be feasible in cohort studies in which sample size is necessarily limited and very large resources are needed to maintain high follow-up rates over a long period, it will be extremely difficult to collect evidence for the long-term independent effects of exclusive breastfeeding and partial formula feeding. Nevertheless, breast-feeding seems to be one of those rare etiologic factors that has biologically plausible effects for which there is consistent evidence that is potentially open to public health promotions and for which there is now substantial evidence of its influence on the subsequent health of children. From a public health perspective, it has become important to convince mothers to consider the health effects for their children that last for a long time beyond the period of breast-feeding. To achieve this, breast-feeding will need to be widely promoted and strategies put in place to support all women who choose to breast-feed, including those who return to work. In the home, support services may include ready access to professionals with expertise in infant feeding practices. In the workplace, supportive strategies may include the provision of facilities for feeding or expressing, flexible work options, and acceptance from colleagues. In the general community, active education through local health care agencies to promote the benefits of breast-feeding and to reduce opposition to
J ALLERGY CLIN IMMUNOL SEPTEMBER 1999
breast-feeding in public places will be needed. In addition, government initiatives to provide adequate maternity leave in all workplaces will facilitate breast-feeding by helping to ensure that mothers have prolonged personal contact with their babies. From a public health perspective, it would seem important that all babies receive breast milk for as long as possible. Early evidence from research studies10,24 and a recent systematic review25 shows that communitybased trials of breast-feeding promotion and extra support from professionals with special skills in early infant feeding are effective in prolonging breast-feeding. Because breast-feeding rates remain less than optimal in many countries, public health strategies to further promote the beneficial effects of breast-feeding, to prevent babies from unnecessary early exposure to formula feeding, and to support all mothers who choose to breast-feed are urgently required. Health goals to increase breastfeeding rates at least to those of Scandinavian countries would not seem unreasonable. The increasing evidence that exclusive breast-feeding plays an important role in the prevention of systemic and allergic illnesses throughout childhood suggests that any public health strategies that increase the prevalence and the duration of breast-feeding will provide many important health benefits for future generations of children. One of the health benefits will be the down-regulation of allergic sensitization and the subsequent prevention of the onset of allergic and asthmatic symptoms in later childhood. Jennifer K. Peat, PhD Clinical Epidemiology Unit PO Box 3515 Parramatta, NSW, Australia Jane Allen, PhD James Fairfax Institute of Paediatrics University of Sydney New Children’s Hospital Westmead, Australia Wendy Oddy, MPH TVW Telethon Institute for Child Health Research West Perth, Australia REFERENCES 1. Grummer-Strawn LM. The effect of changes in population characteristics on breastfeeding trends in fifteen developing countries. Int J Epidemiol 1996;25:94-102. 2. Heinig MJ, Dewey KG. Health advantages of breast feeding for infants: a critical review. Nutrition Res Rev 1996;9:89-110. 3. Raisler J, Alexander C, O’Campo P. Breast-feeding and infant illness: a dose-response relationship? Am J Public Health 1999;89:25-30. 4. Hunter HH. Why many more women breastfeed in Norway than in Britain. New Generation J NCT 1996;15:26-7. 5. Cunningham AS, Jelliffe DB, Jelliffe EFP. Breast-feeding and health in the 1980s: a global epidemiologic review. J Pediatr 1991;118:659-66. 6. Wold AE, Adlerberth I. Does breastfeeding alter the infant’s immune responsiveness? Acta Paediatr 1998;87:19-22. 7. Hanson LA, Hahn-Zoric M, Berndes M, Ashraf R, Herias V, Jalil F, et al. Breast feeding: overview and breast milk immunology. Acta Paediatrica Jpn 1994;36:557-61. 8. Nafstad P, Jaakkola JJK, Hagen JA, Botten G, Kongerud J. Breastfeeding, maternal smoking and lower respiratory infections. Eur Respir J 1996;9:2623-9.
J ALLERGY CLIN IMMUNOL VOLUME 104, NUMBER 3, PART 1
9. Wilson AC, Forsyth JS, Greene SA, Irvine L, Hau C, Howie PW. Relation of infant diet to childhood health: seven year follow up of cohort of children in Dundee infant feeding study. BMJ 1998;316:21-5. 10. Wright AL, Bauer M, Naylor A, Sutcliffe E, Clark L. Increasing breastfeeding rates to reduce infant illness at the community level. Pediatrics 1998;101:837-44. 11. Duncan B, Ey J, Holberg CJ, Wright AL, Martinez FD, Taussig LM. Exclusive breast-feeding for at least 4 months protects against otitis media. Pediatrics 1993;91:867-72. 12. Wold AE, Hanson LA. Defense factors in human milk. Curr Opin Gastroenterol 1994;20:652-8. 13. Chandra RK, Singh G, Shridhara B. Effect of feeding whey hydrolysate, soy and conventional cow milk formulas on incidence of atopic disease in high risk infants. Ann Allergy 1989;63:102-6. 14. Saarinen UM, Kajosaari M. Breastfeeding as prophylaxis against atopic disease: prospective follow-up study until 17 years old. Lancet 1995;346:1065-9. 15. Wright AL, Holberg CJ, Martinez FD, Morgan WJ, Taussig LM, Group Health Associates. Breast feeding and lower respiratory tract illness in the first year of life. BMJ 1989;299:946-9. 16. Wright AL, Holberg CJ, Taussig LM, Martinez FD. Relationship of infant feeding to recurrent wheezing at age 6 years. Arch Pediatr Adolesc Med 1995;149:758-63. 17. Burr ML, Limb ES, Maguire MJ, Amarah L, Eldridge BA, Layzell JCM, et al. Infant feeding, wheezing, and allergy: a prospective study. Arch Pediatr Adolesc Med 1993;68:724-8.
Peat, Allen, and Oddy 529
18. Infante-Rivard C. Childhood asthma and indoor environmental risk factors. Am J Epidemiol 1993;137:834-44. 19. Tariq SM, Matthews SM, Hakim EA, Stevens M, Arshad SH, Hide DW. The prevalence of and risk factors for atopy in early childhood: a whole population birth cohort study. J Allergy Clin Immunol 1998;101:587-93. 20. Rylander E, Pershagen G, Eriksson M, Nordvall L. Parental smoking and other risk factors for wheezing bronchitis in children. Eur J Epidemiol 1993;9:517-26. 21. Peat JK, Salome CM, Woolcock AJ. Longitudinal changes in atopy during a 4-year period: relation to bronchial hyperresponsiveness and respiratory symptoms in a population sample of Australian schoolchildren. J Allergy Clin Immunol 1990;85:65-74. 22. Peat JK, Li J. Reversing the trend: reducing the prevalence of asthma. J Allergy Clin Immunol 1999;103:1-10. 23. Yu G, Duchen K, Bjorksten B. Fatty acid composition in colostrum and mature milk from non-atopic and atopic mothers during the first 6 months of lactation. Acta Pediatr 1998;87:729-36. 24. Morrow AL, Guerrero ML, Shults J, Calva JJ, Lutter C, Bravo J, et al. Efficacy of home-based peer counselling to promote exclusive breastfeeding: a randomised controlled trial. Lancet 1999;353:1226-31. 25. Sikorski J, Renfrew MJ. Support for breastfeeding mothers. [Cochrane Review]. In: The Cochrane Library, Issue 1. Oxford: Update Software; 1999.