On the role of fats and soaps in the establishment of infant gut microbiota: the case of Faecalibacterium prausnitzii
The development of the human gut microbiota in the first years of life is associated with long-term health. Upon birth, a diverse mixture of bacteria from the mother and environment will start growing in a newborn’s gut. The bacterial diversity in the infant gut continues to increase for the first three years of life, but this developmental process is vulnerable to perturbations. The present PhD thesis describes how products for personal hygiene, detergents and fats have a negative impact on the development of a diverse and healthy gut microbiota. Specifically, the results show that certain fats included in infant formula can lead to the formation of elevated levels of calcium soaps, especially calcium palmitate, compared to the fats in human breast milk. A key beneficial human gut microbe, Faecalibacterium prausnitzii, turned out to be particularly sensitive to calcium palmitate. This soap perturbs the lipid composition, function and integrity of the bacterial cell envelope. Importantly, other fats can sustain growth of the major infant gut bacteria and F. prausnitzii, similar to the fats in human breast milk. This is an important finding, because the depletion of especially F. prausnitzii is associated with various human diseases, including allergies, asthma and type 1 diabetes. Altogether, it can be concluded that the fat composition of infant formula is a key factor that needs to be addressed in future approaches to further optimize infant formula. If successful, this will help to minimize potentially unhealthy differences in the gut microbiota of breast-fed and bottle-fed infants.