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Key messages

  • There is strong evidence that breastfeeding protects against breast cancer
  • There is strong evidence that breastfeeding promotes healthy growth in babies and protects children against overweight and obesity
  • Where possible, infants should be exclusively breastfed to 6 months
  • Cancer Council Australia supports the Australian Dietary Guidelines to encourage, support and promote breastfeeding


Breastmilk provides babies with all the energy and nutrients they need for the first months of life. The composition of breast milk changes to reflect the infant’s needs and contains proteins, lipids, and carbohydrates. In addition to meeting the infant’s nutrition requirements, breastmilk provides infants with other components that play a role in supporting the development of their immune system and intestinal microbiota. (1)  

Breastfeeding has been shown to increase health outcomes of infants across their lifespan from childhood to adolescence and into adulthood. This includes lower rates of overweight and obesity, type 2 diabetes, and asthma in children who have been breastfed. Children with excess body fat are more likely to carry that into adulthood and that excess body fat increases the risk of many cancers. Additionally breastfeeding protects mother from breast cancer and helps recovery after giving birth.(2)

Epidemiological evidence 

The World Cancer Research Fund (WCRF) found there is strong evidence that lactation (the process by which a mother produces milk to breastfeed, either directly or through pumping/expressing breastmilk) decreases the risk of breast cancer, and limited evidence that it can reduce the risk of ovarian cancer. Additionally, this is consistent with the current literature (3, 4) and recommendations by The Centers for Disease Control and Prevention (CDC) (5) and The World Health Organization (WHO) (6).

Children who have been breastfed have a decreased risk of having excess body fat. Excess body fat often continues into adult life and can increase the risk of many cancers. (2)

Biological mechanism 

Breast cancer

The period of amenorrhea (the absence of menstruation) and infertility during breastfeeding is thought to reduce the risk of breast cancer. During amenorrhea, the body is not exposed to specific hormones which can influence the risk of cancer (e.g. androgens). During lactation, the breast tissues are constantly changing and removing the older cells. This process is also thought to reduce cancer risk. (2)

Ovarian cancer

The mechanisms linking breastfeeding and reduced risk of ovarian cancer have not been well established. However, it is hypothesised that the longer periods of amenorrhea and the suppression of ovulation reduces exposure to hormones. (2)

Excess body fat and weight gain

The mechanisms that reduce the rates of living with overweight or obesity for exclusively breastfed children is unclear. However, theories suggest that it could be linked to the effect of breastfeeding on the gut microbiota (the microorganisms that live in our digestive systems) of the child as well as the different hormones in breastmilk that can regulate satiety and support microbiota development.(7)

Current levels

The 2017-2018 National Health Survey estimated that two-thirds of children aged 4-47 months were exclusively breastfed to at least 4 months of age. (8)  About a third (29%) of children aged 6 months to 3 years were exclusively breastfed to 6 months. Nearly two-thirds (64%) of infants in 2-parent families were exclusively breastfed to at least 4 months of age, compared with less than half of infants (46%) in 1-parent families.

Dietary recommendations

The WHO recommends babies receive only breastmilk for the first six months of their life and continue to receive breastmilk in conjunction with other safe complimentary food and liquids up until 2 years and beyond. (6) In Australia, the National Health and Medical Research Council (NHMRC) also recommends exclusively breastfeeding until around 6 months of age when solid foods are introduced. The guidelines also recommend breastfeeding to continue until 12 months of age and further. (9)

The Australian Dietary Guidelines recommendations include ‘encourage, support and promote breastfeeding.’ It is important that breastfeeding mothers feel supported by their family (including preparing meals, ensuring they have a healthy nutrient-rich diet) and their environment (public spaces and workplaces should provide breastfeeding facilities). (10)

Policy context 

Cancer Council Australia supports:

  • Workplace and local government policy to support breastfeeding including  
    • a flexible working policy to support breastfeeding
    • breastfeeding facilities at worksites and community facilities
  • The Australian National Breastfeeding strategy 2019 and beyond to support, encourage and promote breastfeeding and create an environment where breastfeeding is a social norm (11)
  • Regulation on the marketing of breastmilk substitutes


  1. Andreas NJ, Kampmann B, Le-Doare KM. Human breast milk: A review on its composition and bioactivity. Early human development. 2015;91(11):629-35.
  2. World Cancer Research Fund, American Institute for Cancer Research. Food, nutrition, physical activity, and the prevention of cancer: a global perspective. Washington DC; 2018.
  3. Unar-Munguía M, Torres-Mejía G, Colchero MA, Gonzalez de Cosio T. Breastfeeding mode and risk of breast cancer: a dose–response meta-analysis. Journal of human lactation. 2017;33(2):422-34.
  4. Yang L, Jacobsen KH. A systematic review of the association between breastfeeding and breast cancer. Journal of women's health. 2008;17(10):1635-45.
  5. Centers for Disease Control and Prevention. Breastfeeding for Cancer Prevention 2019 [Available from:
  6. The World Health Organization. Infant and young child feeding 2021 [Available from:
  7. Azad MB, Vehling L, Chan D, Klopp A, Nickel NC, McGavock JM, et al. Infant feeding and weight gain: separating breast milk from breastfeeding and formula from food. Pediatrics. 2018;142(4).
  8. Australian Institute of Health and Welfare. Australia's children 2020 [Available from:
  9. National Health and Medical Research Council. Infant Feeding Guidelines: Summary. Canberra: National Health and Medical Research Council; 2013.
  10. National Health and Medical Research Council. Australian Dietary Guidelines Canberra; 2013.
  11. COAG Health Council. The Australian National Breastfeeding Strategy: 2019 and Beyond. Canberra: COAG Health Council; 2019.