What are the differences in the risk of breast cancer between direct breastfeeding and expressing breast milk?

Direct breastfeeding could cut the chance of breast cancer by up to one fifth. It’s actually a “powerful strategy” to reduce the risk of cancer for you, especially the most aggressive types of disease. Scientists believe the high hormone levels required for lactation appears to affect cell growth, protecting the breast from changes which increase the risk of breast cancer. The fact women do not usually ovulate while producing milk is also understood to protect against cancer of the breast and ovaries.

Breast-milk also provides a direct and non-invasive source of all the types of epithelial cells found in the lactating breast. Thus, it could help delineate mechanisms leading to cancer and potentially, cancer risk.

Whereas, in expressing breast milk you are using your hand to rhythmically compress your breast so that milk comes out which you then collect in a clean container. It's an alternative to a manual or electric pump. But this process is not as effective as direct breastfeeding when you are looking to lower cancer risks. There is an uncertainty whether it confers similar protection to that derived by directly breastfeeding.