Breast Feeding 2-The Risks of Formula Feeding Versus the Benefits of Breastfeeding
Public health campaigns and medical literature have traditionally described the “benefits of breastfeeding,” comparing health outcomes among breastfed infants against a reference group of formula-fed infants. Although mathematically synonymous with reporting the “risk of not breastfeeding,” this approach implicitly defines formula feeding as the norm.
As several authors have noted,this subtle distinction impacts public perceptions of infant feeding. If “breast is best,” then formula is implicitly “good” or “normal.”
This distinction was underscored by national survey data showing that, in 2003, whereas 74.3% of US residents disagreed with the statement: “Infant formula is as good as breast milk,” just 24.4% agreed with the statement: “Feeding a baby formula instead of breast milk increases the chance the baby will get sick.”
These distinctions appear to influence parents’ feeding decisions. In 2002, the Ad Council conducted focus groups to develop the National Breastfeeding Awareness Campaign, targeted at reproductive-aged women who would not normally breastfeed. They found that women who were advised about the “benefits of breastfeeding” viewed lactation as a “bonus,” like a multivitamin, that was helpful but not essential for infant health.
Women responded differently when the same data were presented as the “risk of not breastfeeding,” and they were far more likely to say that they would breastfeed their infants. Given these findings, this review will present differences in health outcomes as risks of formula feeding, using breastfeeding mother-infant dyads as the referent group.
Women responded differently when the same data were presented as the “risk of not breastfeeding,” and they were far more likely to say that they would breastfeed their infants. Given these findings, this review will present differences in health outcomes as risks of formula feeding, using breastfeeding mother-infant dyads as the referent group.
Compared with breastfed infants, formula-fed infants face higher risks of infectious morbidity in the first year of life. These differences in health outcomes can be explained, in part, by specific and innate immune factors present in human milk. Plasma cells in the mother’s bronchial tree and intestine migrate to the mammary epithelium and produce IgA antibodies specific to antigens in the motherinfant dyad’s immediate surroundings, providing specific protection against pathogens in the mother’s environment.
In addition, innate immune factors in milk provide protection against infection. Oligosaccharides prevent attachment of common respiratory pathogens, such as Haemophilus influenzae and Streptococcus pneumoniae, to respiratory epithelium, and glycoproteins prevent binding of intestinal pathogens such as Vibrio cholerae, Escherichia coli, and rotavirus.
In addition, innate immune factors in milk provide protection against infection. Oligosaccharides prevent attachment of common respiratory pathogens, such as Haemophilus influenzae and Streptococcus pneumoniae, to respiratory epithelium, and glycoproteins prevent binding of intestinal pathogens such as Vibrio cholerae, Escherichia coli, and rotavirus.
Glycosaminoglycans in milk prevent binding of HIV gp120 to the CD4 receptor, reducing risk of transmission, and human milk lipids contribute to innate immunity, with activity against Giardia lamblia, H influenzae, group B streptococci, S epidermidis, respiratory syncytial virus (RSV), and herpes simplex virus type 1 (HSV-1).
Approximately 44% of infants will have at least 1 episode of otitis media in the first year of life, and the risk among formula-fed infants is doubled (95% confidence interval [CI], 1.4–2.8) compared with infants who are exclusively breastfed for more than 3 months.1 Human milk oligosaccharides and antibodies to common respiratory pathogens in the infant’s environment are thought to provide protection from infection.
In a meta-analysis of 7 cohort studies of healthy term infants in affluent regions, Bachrach and associates15 found that infants who were not breastfed faced a 3.6-fold increased risk (95% CI, 1.9–7.1) of hospitalization for lower respiratory tract infection in the first year of life, compared with infants who were exclusively breastfed for more than 4 months. These studies included adjustment for parental smoking and socioeconomic status. The majority of respiratory hospitalizations for infants result from infection with RSV. Lipids in human milk appear to have antiviral activity against RSV.
Multiple studies suggest that formulafed infants face an increased risk of gastroenteritis and diarrhea. In a meta-analysis of 14 cohort studies, Chien and Howie found that infants who were formula fed or fed a mixture of formula and human milk were 2.8 times (95% CI, 2.4–3.1) more likely to develop gastrointestinal (GI) infection than those who were exclusively breastfed.
Data from the Promotion of Breastfeeding Intervention Trial (PROBIT) found that infants in the control group were 1.7 times (95% CI, 1.1–2.5) more likely to develop GI illness than those in the intervention group. In this study, Kramer and colleagues randomized 31 maternity hospitals to the Baby Friendly Hospital Initiative (BFHI), a set of evidence-based practices supportive of breastfeeding, versus usual care. All 17,046 infants in the PROBIT study were breastfed, but at 3 months, only 6.4% of control infants were exclusively breastfed compared with 43.3% of intervention infants.
Data from the Promotion of Breastfeeding Intervention Trial (PROBIT) found that infants in the control group were 1.7 times (95% CI, 1.1–2.5) more likely to develop GI illness than those in the intervention group. In this study, Kramer and colleagues randomized 31 maternity hospitals to the Baby Friendly Hospital Initiative (BFHI), a set of evidence-based practices supportive of breastfeeding, versus usual care. All 17,046 infants in the PROBIT study were breastfed, but at 3 months, only 6.4% of control infants were exclusively breastfed compared with 43.3% of intervention infants.
Among preterm infants, not being breastfed is associated with a 2.4-fold risk (95% CI, 1.04–5.6) of NEC with an absolute risk difference of 5%.1 Because the case-fatality rate for NEC is 15%,this difference in absolute risk is clinically significant.
Epidemiologic studies suggest that children who are formula fed in infancy are more likely to become obese or develop type 2 diabetes. In meta-analyses, children formula fed in infancy were 1.1 (95% CI, 1.0–1.1) to 1.3 (95% CI, 1.2–1.5) times as likely to become obese as children who had ever been breastfed. Being formula fed in infancy is also associated with a 1.6-fold risk (95% CI, 1.2–2.3) of type 2 diabetes, compared with being breastfed.
Some studies have also suggested an increase in risk for cardiovascular disease, including higher blood pressure and less favorable lipid profiles,but the literature is mixed. Researchers have proposed several mechanisms to explain these associations, including differences in composition of human milk versus formula, feeding practices, associated lifestyle factors, and self-regulation of intake by the infant.
Moreover, human milk contains adipokines, which may play a role in regulating energy intake and long-term obesity risk.Several authors have postulated that long-chain polyunsaturated fatty acids in breast milk may affect blood pressure and insulin resistance in later life.Nevertheless, observational data must be interpreted with caution because of potential confounding by other lifestyle behaviors in families with long durations of breastfeeding versus formula feeding.
Some studies have also suggested an increase in risk for cardiovascular disease, including higher blood pressure and less favorable lipid profiles,but the literature is mixed. Researchers have proposed several mechanisms to explain these associations, including differences in composition of human milk versus formula, feeding practices, associated lifestyle factors, and self-regulation of intake by the infant.
Moreover, human milk contains adipokines, which may play a role in regulating energy intake and long-term obesity risk.Several authors have postulated that long-chain polyunsaturated fatty acids in breast milk may affect blood pressure and insulin resistance in later life.Nevertheless, observational data must be interpreted with caution because of potential confounding by other lifestyle behaviors in families with long durations of breastfeeding versus formula feeding.
Multiple authors have examined associations between infant feeding and cognitive development, with mixed results. Several studies reported modestly lower IQ scores in formulafed children compared with breastfed children, whereas others reported no association between infant feeding and intelligence. Observational data should be interpreted with caution due to confounding by socioeconomic status and maternal intelligence.
Nevertheless, data from 2 randomized controlled trials provides evidence of developmental differences with shorter durations of breastfeeding. Dewey and associates randomized mothers in Honduras to introduction of complementary foods at 4 months versus continued exclusive breastfeeding until 6 months postpartum. Infants in the complementary food group crawled later than those that were exclusively breastfed from 4 to 6 months (P = .007).
Among normal birth weight infants, those who were randomized to complementary foods before 6 months were less likely to be walking at 12 months (39 vs 60%; P = .02). Kramer and colleagues similarly found differences in neurodevelopment with shorter breastfeeding in the PROBIT study. At age 6.5 years, verbal IQ scores were 7.5 points lower (95% CI, −0.8 to −14.3) among children in the usual care group than among children in the breastfeeding support group. Kramer’s results suggest that hospital policies that support breastfeeding can impact neurodevelopment at school age.
Nevertheless, data from 2 randomized controlled trials provides evidence of developmental differences with shorter durations of breastfeeding. Dewey and associates randomized mothers in Honduras to introduction of complementary foods at 4 months versus continued exclusive breastfeeding until 6 months postpartum. Infants in the complementary food group crawled later than those that were exclusively breastfed from 4 to 6 months (P = .007).
Among normal birth weight infants, those who were randomized to complementary foods before 6 months were less likely to be walking at 12 months (39 vs 60%; P = .02). Kramer and colleagues similarly found differences in neurodevelopment with shorter breastfeeding in the PROBIT study. At age 6.5 years, verbal IQ scores were 7.5 points lower (95% CI, −0.8 to −14.3) among children in the usual care group than among children in the breastfeeding support group. Kramer’s results suggest that hospital policies that support breastfeeding can impact neurodevelopment at school age.
These studies were conducted prior to use of formula supplemented with long-chain polyunsaturated fatty acids (LCPUFA), which had been added to infant formula with the goal of improving neurocognitive outcomes. However, a recent Cochrane meta-analysis concluded that most well-conducted randomized trials showed no benefit of LCPUFA versus control formula on visual acuity or neurodevelopment among term infants. These findings make it unlikely that LCPUFA-supplemented formula would reduce the differences in outcomes between children in intervention and control groups in these studies.
Case-control studies suggest that formula feeding is associated with a 1.6-(95% CI, 1.2–2.3) to 2.1-fold (95% CI, 1.7–2.7) increased odds of SIDS compared with breastfeeding. These associations persisted after adjustment for sleeping position, maternal smoking, and socioeconomic status. In reviewing the evidence, the American Academy of Pediatrics Task Force on Sudden Infant Death Syndrome concluded that factors associated with breastfeeding, but not breastfeeding per se, were associated with a lower incidence of SIDS.
After adjusting for maternal age, education, smoking status, infant race, gender, birth weight, congenital malformation, birth order, plurality, and Women, Infants and Children Nutrition Program status, formula feeding is associated with a 1.3-fold (95% CI, 1.1–1.5) higher risk of infant mortality in the United States compared with ever breastfeeding.In a subgroup analysis, the association was limited to SIDS and injury-related death.
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