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Exposure to breast milk in infancy and risk of adult breast cancer: more scientific data are needed
  1. L A Wise1,
  2. L Titus-Ernstoff2
  1. 1Slone Epidemiology Center, Boston University, Boston, Massachusetts, USA
  2. 2Dartmouth Medical School, Norris Cotton Cancer Center and Hood Center for Children and Families, Lebanon, New Hampshire, USA
  1. Correspondence to Lauren A Wise, Slone Epidemiology Center, Boston University, 1010 Commonwealth Avenue, Boston, MA 02215, USA; lwise{at}

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There has been considerable interest in the health-related benefits of breastfeeding for the infant. Although there are many established short-term benefits of breastfeeding for infant nutrition and health, the potential long-term benefits regarding chronic disease and cancer morbidity in adulthood, including risk of breast cancer, are still unclear. In this editorial, we review the evidence regarding the association between being breast-fed in infancy and the risk of short-term and long-term health outcomes and then focus specifically on breast cancer as an outcome. Finally, we recommend approaches for improving future epidemiologic studies that investigate the effects of exposure to breast milk in infancy on longer-term health.

Most paediatric and nutritional organisations in the USA recommend exclusive breastfeedingi for the first 6 months of life, and breastfeeding with nutritionally adequate and complementary foods for at least 12 months.1 The WHO recommends extending the latter time period for up to 2 years of age or beyond.2 The prevalence of breastfeeding in the USA is lower than that in Western Europe and other nations. In the USA, approximately 33% to 36% of infants are breastfeeding at 6 months of age, and 17% to 20% of infants are breastfeeding at 12 months of age, whereas worldwide, 79% of infants are still breastfeeding at 12 months.1

Most literature on the health effects of being breast-fed in infancy pertain to short-term health effects and illnesses in childhood. In a 2007 review3 of published literature regarding the effects of breastfeeding on child health outcomes were associated with a reduced risk of acute otitis media, non-specific gastroenteritis, necrotising enterocolitis, respiratory tract infections, atopic dermatitis, early-onset asthma, childhood obesity, type 1 diabetes, …

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  • Funding The authors are funded by the National Institutes of Health, but the article itself is not.

  • Competing interests None.

  • Provenance and peer review Commissioned; externally peer reviewed.

  • i World Health Organization defines exclusive breastfeeding as no other food or drink, not even water, except breast milk (including expressed milk or milk from a wet nurse) but allows the infant to receive oral vitamins, minerals and medicines.