Scientists discover a biological "memory" of breastfeeding in child blood samples

Babies who are exclusively breastfed for at least three months carry markers in their blood that differ from babies who are not breastfed.

The finding comes from the largest study of its kind, conducted across an international consortium. Researchers studied blood sample data in children, looking at epigenetic marks across the genome. Epigenetics refers to chemical changes to DNA which influence which genes are active and how they function. Specifically, the team looked at the epigenetic process of DNA methylation, a chemical process which can be detected in blood samples.

The research was led by the Barcelona Institute for Global Health (ISGlobal), the University of Exeter and the University of Bristol and was published in Clinical Epigenetics. The study found DNA methylation marks on genes associated with immunity and developmental processes were higher on average in children who had been exclusively breastfed for at least three months, compared to those who had not been breastfed.

However, the study did not look at whether the children had any difference in their immunity or development as a result of carrying these epigenetic marks.

Our findings show that babies who are exclusively breastfed carry epigenetic changes associated with that experience. The genes that are affected by these markers are involved in developmental and immunity processes, but we can't say from our study whether this affects those highly complex processes directly. "

Dr. Doretta Caramaschi, University of Exeter

Research has shown separately that breastfeeding is associated with short- and long-term beneficial effects on child health.

Dr Mariona Bustamante, of ISGlobal, an institution supported by the la Caixa Foundation, added: "Our results are new and interesting, but we do need to interpret them with some caution. Our study is designed to be collaborative and international, however, we need to study more diverse groups to fully understand this biology."

The research was conducted via the Pregnancy and Childhood Epigenetics (PACE) Consortium, made of 11 studies internationally, in countries including Spain, the Netherlands, Finland, France, Greece, Lithuania, Germany, South Africa and US, including a cohort of mixed ethnicity. In the UK, the study involved the Bristol-based Children of the 90s study, the Born in Bradford study and the Isle of Wight Birth Cohort Study. The analysis incorporated epigenetic data from 3,421 children across these studies.

Researchers looked at whether the babies were breastfed and for how long and whether they were exclusively breastfed, and for how long. Information on breastfeeding was collected through questionnaires from birth. DNA methylation marks were measured from samples taken when the children were aged 5 to 12 years, and compared to those in samples taken from the umbilical cord to assess pre-breastfeeding. Researchers examined whether there was any difference related to the experience of being breastfed.

The study was published in Clinical Epigenetics with funding from multiple sources including the Medical Research Council, Wellcome, and Horizon 2020.