Breastfeeding Update 1: Immunology, Nutrition, and Advocacy

Most pediatricians are knowledgeable about the advantages of breastfeeding, especially exclusive breastfeeding for the first 6 months of an infant’s life. These benefits in developed countries include a reduction in the incidence of infectious disease (in particular, diarrhea, otitis media, upper respiratory tract infections, pneumonia, and urinary tract infections), provision of complete nutrition that sustains adequate growth and hydration of the infant in the first 6 months of life, prevention of disease and allergy, improved child spacing, and psychosocial benefits.Despite our understanding of the numerous benefits of breastfeeding, a number of studies have found that health-care providers represent one of the major barriers to successful breastfeeding. In 1993, United States statistics revealed breastfeeding initiation rates of 55.9%. At 6 months postpartum,continuation rates for breastfeeding were only 19%. One might ask, “How can so few women breastfeed when the American Academy of Pediatrics (AAP)recommends that all infants be breastfed exclusively for the first 4 to 6 months of life and continue to be breastfed for a year or more?” (The World Health Organization [WHO] and United Nations Children’s Fund [UNICEF]recommend continuation for 2 years or more.) However, one might also ask,“How can so many women in the United States successfully breastfeed with little support from health-care professionals?”A pediatrician’s ability to advocate for and promote breastfeeding is based on many factors,including: 1) the strong belief that human milk is the optimal food for the infant, 2) an affiliation with obstetricians who support breastfeeding, 3)clinical skills to support and manage breastfeeding families, 4) the ability to refer to more knowledgeable healthcare providers and support groups when indicated, 5) an affiliation with maternity hospitals that have policies and procedures that support breastfeeding, 6) the establishment of a“breastfeeding culture” in the office and hospital, 7) belief in the importance of continuing breastfeeding even if the mother works out of the home, and 8) a conscious effort to avoid the promotion of infant formula products. (See Appendix for concrete suggestions on breastfeeding promotion.)Many resources beyond formula manufacturers are available to supply information and educational materials (Table 1). The support of family members is crucial to breastfeeding success (FigureF1). Health professionals and lay groups have emphasized paternal involvement in encouraging and supporting his partner in breastfeeding. Clinicians should state explicitly the expectations that the father of the baby be involved in prenatal preparations, including parent education about breastfeeding. Frequently it is necessary to describe the many ways that fathers can bond with their newborn infants other than by feeding: holding, playing, singing, changing,bathing, burping, carrying, rocking, or bringing the baby to the mother for feedings. Fathers also can assist with feeding by performing household chores, shopping for food, preparing meals, or performing other tasks that allow mother and baby to get breastfeeding well established in the early weeks.The Baby Friendly Hospital Initiative, launched by WHO and UNICEF in 1991, is a campaign to improve breastfeeding rates worldwide. The “Ten Steps to Successful Breastfeeding” (Table 2) provide the basis of care in maternity hospitals that fully support breastfeeding. More than 6,000 hospitals have been designated as Baby Friendly in 159 foreign countries. Efforts in the United States have lagged behind other countries, but as of January 1996, 309 hospitals (including 18 birthing centers) in 43 states have received “Certificates of Intent” to become Baby Friendly under the auspices of the United States Committee for UNICEF, and one hospital has received the designation.Breastfeeding promotion is in the best interests of patients, physicians, and institutions. In this era of cost containment, increasing the initiation and duration of breastfeeding is one way to reduce health-care costs. Dr. Miriam Labbok estimates that if full breastfeeding were practiced for 12 weeks in the United States, 2.16 billion dollars would be saved annually (using illness as a sole indicator of cost).To bolster your confidence regarding the benefits of breastfeeding/human milk and to strengthen your resolve to become an active advocate, we discuss some highlights of recent research regarding the immunologic and nutritional aspects of human milk.Studies of the immune system of human milk provide indisputable evidence that it is the optimal food for the infant and that there really is no such thing as a substitute. As Dr. Armond Goldman so nicely describes (see Suggested Reading), the immune system of human milk provides for a continuum of the maternal immune protection that extends from transplacental transfer of immunoglobulin G(IgG) in utero until the second year of life. Human milk furnishes the necessary immunologic protection while the infant’s immune system is maturing. Production of secretory IgA in the infant begins at about 4 months and is not fully established until 12 months of age, production of the full antibody repertoire is not fully mature until about 24 months of age,lysozyme production is not fully mature until 1 to 2 years of age, and production of memory T cells in the infant is not mature until about 2 years(Table 3). Although numerous other immunologic components have been identified, their maturation patterns are not well established. It is no wonder that breastfed infants are at lower risk for infections, with the human milk immune system compensating for their own immature immune systems.Human milk contains three major categories of immunologic factors:antimicrobial agents, anti-inflammatory agents, and immunomodulating agents. The list of factors in each category grows longer each year as more and more properties of human milk are identified. For example, in one study, after exposure to respiratory syncytial virus, breastfed infants had significantly higher levels of serum alpha interferon than did formula-fed infants. The fact that alpha interferon is not measurable in human milk suggests that direct transfer is not occurring. Rather, human milk appears to contain an“immunomodulator” that “turns on” the infant’s own production of interferon. Lactoferrin has been shown to operate in a similar manner in each sector of the immune system of human milk. In light of these discoveries, formula appears less than adequate in terms of replacing human milk.The antimicrobial agents in human milk illustrate the unique interaction between infant and mother in responding to environmental challenges. For example, within a few days of maternal exposure to pathogens such as Shigella, antibodies to this bacterium are noted in the mother’s milk, which confers protection to the breastfeeding infant. This is due to the enteromammory circulation pathway, which is triggered by antigen exposure to B cells (IgM+) from the Peyer patches of the lower small intestinal tract and the consequent migration of those isotype-switched B cells (IgA+) to the lamina propria of the mammary gland with the help of cytokines. At the mammary gland, the transported B cells differentiate into IgA-producing/secreting plasma cells, and through a number of steps within the mammary gland, secretory IgA is formed and secreted. A similar pathway for B cell migration from the lymphoid centers in the bronchial tree to the lamina propria of the mammary gland is called the bronchomammary pathway. Thus, it is not surprising to find specific secretory IgA antibodies for a wide spectrum of bacterial, viral, and protozoal antigens (Table 4). Secretory IgA (SIgA) is the major antibody in human milk; a fully breastfed infant receives 0.5 to 1 g of SIgA orally per day.As Goldman has summarized, SIgA and the other antimicrobial agents present in human milk(Table 5) are resistant to digestive enzymes, confer protection without triggering inflammatory reactions, compensate for the infant’s inability to process antimicrobial agents, kill certain bacterial pathogens synergistically, and are common to mucosal sites. Note the differences in the presence of antimicrobial agents between human and bovine milk (Table 6), illustrating the species specificity of human milk for the human infant.The anti-inflammatory agents present in human milk represent a complex group of immune factors whose roles have not been elucidated completely (Table 7). Acetylhydrolase, an enzyme that degrades platelet activating factor, is present in human milk and may play a role in the decreased risk of necrotizing enterocolitis in the preterm infant fed human milk. Another anti-inflammatory agent present in human milk,epithelial growth factor, may explain why infants who continue to breastfeed through diarrheal infections recuperate sooner and experience less morbidity than formula-fed infants.Feeding of human milk not only reduces rates of infections, but it also decreases the risk for immunologically associated disorders, such as atopy, in infants from families at high risk. Dr. Anne Wright and coworkers from Arizona found that 11% of recurrent wheezing among nonatopic children studied was attributed to not breastfeeding. It is hypothesized that protection against atopic disease is due not only to decreased exposure to potential allergens such as soy proteins and cow milk proteins that are present in formulas, but to the protection associated with the anti-inflammatory agents present in human milk. The current breastfeeding recommendation that infants exclusively breastfeed for the initial 4 to 6 months of life is especially important for infants who have a strong family history of atopic disease. For families that have a strong history of atopy, some allergists recommend avoidance of all cow milk-based products in the maternal diet for the last trimester of pregnancy and during lactation.The complex role of human milk in maintaining the health of the infant is well represented by the immuno-modulating factors, including cytokines, alphatocopherol,beta-casomorphins, and prolactin. These agents may play a role in disease prevention after infancy and be factors in the decreased risk for breastfed infants to develop Crohn disease, insulin-dependent diabetes, and lymphoma. The immunomodulating role of cytokines (Table 8) has been documented to include the possible functions of activating T cells, enhancing IgA and secretory component production, and participating in the entero- and bronchomammary circulation. All of these processes potentiate the infant’s infection fighting response.It is clear that human milk plays a vital role in the immunologic development of the infant at birth and well into the second year. Its nutritional role also is clearly superior to that of other alternatives. Case reports and media hype accentuate concerns about what might be lacking in human milk, but all of the necessary nutrients and water are provided by human milk for the first 6 months of an infant’s life with the exception of: Infants thrive on exclusive human milk for the first 6 months of life,although excuses frequently are made to start foods earlier.One common misperception is that the addition of solid foods to the diet will lengthen night sleep episodes; no evidence supports this belief. In addition, the myth of infants sleeping through the night is partially dispelled by one study in Australia that showed that more than 50% of the infants studied did not sleep through the night at 1 year of age.Human milk contains significantly less protein than does cow milk (Table 9). The protein composition in human milk also is very different from that of formula. Human milk has a high whey:casein ratio of 90:10 at 4 to 10 days post-partum, 60:40 in mature milk at 11 to 240 days, and 50:50 in late lactation at 241+ days,reflecting the developmental stages of the infant’s ability to digest the casein proteins. Formulas contain the opposite set ratio, ranging from 20:80 to 50:50 whey to casein, depending on the brand. The difference in protein composition between human milk and formula results in digestion times of 1.5 hours for breastfed infants compared with 4 hours for formula-fed infants. This underscores the need for infants fed human milk to be fed on demand and as often as demanded, especially in the early weeks when the whey:casein ratios are the highest. The shorter digestion time of human milk also contributes to less gastroesophageal reflux among breastfed infants compared with those fed formula.Breastfed infants need to be fed at night to maintain growth and to receive consistent responses to hunger cues. In addition, night feedings often are necessary to maintain adequate milk production. Pediatricians need to be aware of this when advising mothers about infants’ sleeping habits. Care should be taken not to frown upon mothers who continue to feed their infants at night or who sleep with their babies because these are normal physiologic processes for the breastfeeding mother-infant couple. Strategies on how a mother can minimize awakening when feeding at night is a supportive step for breastfeeding families.Mothers should be made aware that introduction of formula or cereal prior to 6 months of age as a strategy to increase sleeping at night has not been proven to be effective. Further, with the formula replacing human milk,human milk production eventually will diminish significantly. Introducing formula or cereals also decreases the nutritional value of human milk by interfering with the absorption of minerals.A transition to additional foods is appropriate at about 6 months of age. Human milk accounts for 100% of energy needs at 6 months; at 12 months it still may account for 20% to 35% of the infant’s total energy intake. During this transitional period, the energy density and micronutrient content of complementary food must be considered. A detailed discussion of the weaning process is beyond the scope of this article. For additional information, refer to Satter’s book listed in Suggested Reading.Breastfed infants never need to be bottle-fed; they can graduate directly to a cup for drinking human milk when separated from their mother. For families who are more comfortable giving human milk in a bottle, 4 to 6 weeks of age (when breastfeeding usually is well established)is a reasonable time to introduce a bottle.Most concerns about the composition of human milk are cloaked in cultural tradition and personal anecdotes. The following list reviews some common myths about human milk composition, followed by information addressing these issues.When one reviews the wealth of information about the advantages of breastfeeding, there can be no doubt that this practice is healthy for both mother and infant. It is time for the “culture of medicine” to move beyond slogans. It is time for enthusiastic encouragement backed by meaningful action and time to move forward from personal perceptions and experiences to demonstrate to the culture at large that breastfeeding is normal, expected, and achievable.• Work as a team with obstetricians who share your patients.• Have an open attitude toward breastfeeding in waiting areas (or designate a separate breastfeeding room).• Educate yourself and office staff about specifics of breastfeeding clinical care.• Display tasteful, noncommercial educational materials and artwork that depict breastfeeding women.• Create a bulletin board for photos of breastfed babies (they don’t have to be breastfeeding in the photo).• Identify and eradicate unspoken support for bottle feeding in your office/institution.• Facilitate a mother-to-mother support group for your practice.• Encourage and support “baby friendly” policies and practices in your hospitals (see Table 2).• Be familiar with other community resources for breastfeeding help,such as lactation consultants, mother-to-mother support groups, and some WIC sites.• Provide outreach to major employers in your communities.• Review your policy (or develop one) regarding acceptance of free samples from infant formula companies.• Support, encourage, and clinically assist all working mothers who breastfeed (whether they work at home or outside of the home).• Keep statistics on differences in your patients who breastfeed versus those who do not.• Use your influence in the community at large to promote breastfeeding.