Babies who are exclusively breastfed for at least three months show distinct biological markers in their blood compared to those who are not breastfed, according to a major international study.
The research, one of the largest of its kind, analysed blood samples from children to examine epigenetic patterns across the genome. Epigenetics involves chemical modifications to DNA that influence how genes are switched on or off. In particular, scientists focused on DNA methylation—a process detectable in blood that can affect gene activity.
Led by the Barcelona Institute for Global Health, University of Exeter, and University of Bristol, the study—published in Clinical Epigenetics—found higher levels of DNA methylation in genes linked to immunity and development among children who had been exclusively breastfed for at least three months.
However, researchers cautioned that the study did not assess whether these molecular differences translate into measurable changes in health, immunity, or development.
Co-lead researcher Doretta Caramaschi of the University of Exeter said the findings indicate that exclusive breastfeeding leaves a detectable biological imprint. She noted that while the affected genes are tied to key developmental and immune processes, the study cannot establish whether these changes directly influence those outcomes.
The findings build on existing evidence suggesting breastfeeding is associated with both short- and long-term health benefits in children, though the exact biological mechanisms remain under investigation.
Mariona Bustamante of ISGlobal added that while the results are promising, they should be interpreted cautiously. She emphasised the need for more diverse study populations to better understand how these biological changes operate across different groups.
The study was conducted through the Pregnancy and Childhood Epigenetics Consortium, which brings together data from 11 studies across countries including Spain, the Netherlands, Finland, France, Greece, Lithuania, Germany, South Africa and the United States. UK contributions included the Children of the 90s study, Born in Bradford, and the Isle of Wight Birth Cohort.
In total, researchers analysed epigenetic data from 3,421 children. Breastfeeding information—such as duration and exclusivity—was collected from birth through questionnaires. DNA methylation patterns were measured in blood samples taken between ages five and 12 and compared with umbilical cord samples to assess changes following birth.
The analysis aimed to determine whether early-life feeding practices leave lasting biological signatures—an area that continues to offer new insights into how early nutrition may shape long-term health.
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