Urolithins in Human Breast Milk after Walnut Intake and Kinetics of Gordonibacter Colonization in Newly Born: The Role of Mothers' Urolithin Metabotypes

The maternal-infant transmission of several urolithins through breastmilk and the gut colonization of infants by urolithin-producing bacterium Gordonibacter during their first year of life were explored. Two trials (Proof of concept study: n = 11; Validation study: n = 30) were conducted where breastfeeding mothers consumed walnuts as a dietary source of urolithin precursors. An analytical method was developed and validated to characterize the urolithin profile in breastmilk. Total urolithins ranged from 8.5 to 176.9 nM while they were not detected in breastmilk of three mothers. The mothers’ urolithin-metabotypes governed the urolithin profile in breastmilk, which might have biological significance on infants. A specific qPCR method allowed monitoring the gut colonization of infants by Gordonibacter during their first year of life, and neither breastfeeding nor vaginal delivery was essential for this. The pattern of Gordonibacter establishment in babies was conditioned by their mother's urolithin-metabotype, probably because of mother-baby close contact.