Breast milk: diet during pregnancy is crucial

The impact of diet on the composition of breast milk is higher during pregnancy than during lactation, and this composition is known to play a role in the development of newborns’ gut microbiota.


The feeding method will directly influence the composition of the gut microbiota of newborns. The gastrointestinal tract of breastfed newborns contains more bifidobacteria and lactobacilli than that of formula-fed babies. But how is the microbiota of breast milk modulated? Several studies indicate that the mother’s diet during pregnancy and lactation has an influence on its composition. And more recently, another hypothesis suggests that bacteria found in the mother’s gut microbiota migrate to the mammary gland.

Two dominant bacterial genera

To get a clearer picture, a team of Brazilian researchers analyzed the microbial composition of breast milk from 94 women who recently gave birth. Among the 85 identified bacterial genera, 3 were systematically present and 10 were found in the composition of at least 90% of milk samples analyzed. Two genera were largely dominant: streptococci and staphylococci, which are believed to trigger the colonization of the gastrointestinal tract of babies. Bifidobacteria and lactobacilli, which are abundant in the gut microbiota of breastfed babies, were also present but in lower amounts.

Effect of vitamin C and polyunsaturated fatty acids

The researchers then examined the effects on the microbiota of diet during pregnancy and during the first month of breastfeeding. Their two main findings were:

- Only the consumption of vitamin C during pregnancy was associated to a specific bacterial profile, dominated by staphylococci, suggesting that is has an impact on the microbiota of breast milk.

- The consumption of polyunsaturated fatty acids (Salmon, tuna...) during the lactation period slightly modulated the abundance of bifidobacteria.

A different influence before and after delivery

A woman’s diet seems to have an effect on the microbial diversity of her milk. But this influence appears to be stronger during pregnancy than during the lactation period.



Padilha Marina, Danneskiold-Samsøe Niels Banhos, Brejnrod Asker et al. The Human Milk Microbiota is Modulated by Maternal Diet. Reproductive Health. Microorganisms 2019, 7, 502; doi:10.3390/microorganisms7110502