Spanish researchers Maria Carmen Collado, from the Institute of Agrochemistry and Food Technology (IATA-CSIC) and Alex Mira, from the Higher Public Health Research Centre (CSISP-GVA), traced the bacterial content in breast milk.
"This is one of the first studies to document such diversity using the pyrosequencing technique (a large scale DNA sequencing determination technique)," explain Collado and Mira, the American Journal of Clinical Nutrition reported.
"We are not yet able to determine if these bacteria colonise the mouth of the baby or whether oral bacteria of the breast-fed baby enter the breast milk and thus change its composition," outline the authors, according to an IATA and CSISP statement.
The heavier the mother, the fewer the bacteria. The study also reveals that the milk of overweight mothers or those who put on more weight than recommended during pregnancy contains a lesser diversity of species.
The type of labour also affects the microbiome (bacterial content) within the breast milk: that of mothers who underwent a planned caesarean is different and not as rich in micro-organisms as that of mothers who had a vaginal birth.