The Science of Breast Milk

Breast milk is often called “nature’s first vaccine” and, in this week's podcast, Luke O’Neill explains why. From the moment a baby is born, its immune system is still immature and wide open to infection. Breast milk steps in as the baby’s first line of defence, passing on antibodies, immune cells and even the benefits of vaccines the mother has received.

Luke explores how this “passive immunisation” works – from the placenta before birth to breast milk afterwards – and why it’s so powerful in protecting babies against infections, hospitalisations and even long-term risks like obesity and diabetes. He also looks at the benefits for mothers, including protection against breast and ovarian cancer, diabetes and high blood pressure.

Along the way we learn why Ireland still struggles with low rates of breastfeeding, how more support for new mothers could ease pressure on the health system, and why vaccinating during pregnancy is such a vital public health tool. Luke highlights new research on the RSV vaccine, which shows up to 80% protection for babies when mothers are immunised, and pays tribute to Dublin-born scientist Francis Bramble, who first uncovered the secrets of mother-to-baby immunity back in the 1930s. With a wink, Luke suggests it might be time to “Make Bramble Great Again.”

This episode is a reminder that breast milk isn’t just food – it’s medicine, protection, and an immune system tutor all rolled into one.

Send your feedback or ideas for future episodes to Luke at laoneill@tcd.ie.