When researchers compared the stools of 40 infants who were exclusively breast-fed with those of 13 who were exclusively formula-fed, the average daily stool frequency was significantly higher in the breast-fed than formula-fed infants during the first month of life (4.9 vs 2.3) and second month of life (3.2 vs 1.6).

The Acta Paediatrica study also found that the stools were more liquid in the breast-fed infants during the first 3 months, and infrequent stools were 3.5 times more likely in the breast-fed infants (28%) than formula-fed infants (8%).

“The underlying mechanisms of the infrequent stools syndrome in exclusively breast-fed infants are unknown,” the authors wrote. “Many hypotheses have been put forward, from better digestion of the fat in mother’s milk than formula milk to a greater number of saccharolytic bacteria that can degrade unabsorbed and unabsorbable sugars.”