Breastfeeding boosts baby’s immune system

Researchers at Birmingham University, led by Gergely Toldi, Institute of Immunology and Immunotherapy, who is a member of the Academy of Young Researchers, have proved that the number of regulatory T cells in the immune system of babies exclusively breastfed is significantly higher in the first three weeks of their lives than in the immune systems of babies fed with formula milk only. This adds to the health advantages of breastfeeding, some of which have effects lasting until adulthood.

2021. február 18.

Breast milk provides the best nutrition for newborn babies and infants. Several studies have proved that breastfed babies are less susceptible to asthma, obesity and autoimmune diseases than babies receiving formula milk. However, it is important to highlight that this does not mean that formula milk is harmful. A lot of mothers cannot breastfeed their babies because their bodies do not produce enough milk, for example, or they must take medication that excludes breastfeeding. Therefore, mothers feeding their babies with formula should not be stigmatised; this is a possible and accepted way to care for infants.

Toldi Gergely

At the same time, it is doubtless that the composition of breast milk is ideal for babies. As the research of Gergely Toldi and his colleagues proves, the immune system is crucially affected by feeding. It has long been acknowledged that breastfeeding influences the immune system of babies, but very little was known of the exact mechanism. Toldi’s research has revealed that

the number of regulatory T cells produced in the first weeks of life is almost twice as high in exclusively breastfed babies compared with those who received formula milk only.

As their name suggests, these kinds of cells play a role in regulating the immune response. They mitigate the immune reaction triggered by maternal cells in the mother’s milk and reduce inflammation. It has also been revealed that the amount of certain beneficial intestinal bacteria that facilitate the operation of regulatory T lymphocytes is higher in the digestive systems of breastfed babies. The study exploring the relationship between breastfeeding and T cells has been published in the journal Allergy.

“We examined full-term babies born from complication-free pregnancies via cesarean section. This latter factor was important because vaginal birth induces an inflammatory response from the immune system, and this fact would have interfered with the results”, said Toldi. “Right after the neonate’s birth, blood and feces samples were taken from them, which was repeated in three weeks. We examined how the T lymphocytes (i.e. type of immune cells) change in the first week of life and how the baby’s immune cells react to maternal cells.”

During pregnancy, some maternal cells get into the fetus’s organism through the placenta. Furthermore, if the baby is breastfed, maternal cells get into the infant’s circulatory system through the intestines. As Dr Toldi said, “Earlier it had not been known what this phenomenon means from an immunological perspective and what reactions these maternal cells induce. As the research on the human microbiome has been developing dynamically in the past decades, in this experiment the composition of the breastfed babies’ microbiomes and that of the formula-fed control group were also analysed.”

“Our results have proved that considerable changes take place in acquired immunity during the first three weeks of life. No results on humans have been obtained up to now, as it is not easy to get blood samples from healthy infants for research. Our knowledge in this field is gained from animal experiments primarily”, the neonatologist added.

“The amount of regulatory T cells proved to be significantly higher in breastfed babies than in formula-fed infants: their number is nearly twice as high in breastfed neonates by the end of the third week compared to that of the control group.

This cell type regulates the immune response. It plays a role in inflammatory and autoimmune diseases and in fighting infections. The immune response does not only need to be triggered, but it must also be stopped: this is the job of T lymphocytes.”

Maternal cells contain antigens that are not known to the newborn baby’s immune system. With a lack of regulation, the immune system would strongly fight them. Consequently, if the number of regulatory T cells is higher in the organism, it allows for better tolerance of the maternal cells.


This research examined the number of cells in the immune system of neonates.
This experiment does not provide direct information on whether these differences affect the infants’ state of health, their diseases and the future condition of their immune systems. In the future, scholars are planning to follow the long-term development of the babies participating in the present survey. This was the reason why the second blood sample was taken at the very early age of three weeks. In England, neonates do not get mandatory vaccines before this age (BCG vaccination is not compulsory there either). Therefore, there are few things which might affect the immune systems of babies before this age besides breast milk.

However, other epidemiological studies have proved that typical changes occur in the regulatory T cells in allergic patients or in those with autoimmune diseases and those suffering from infections. The present study does not shed light on whether this early difference in the number of regulatory T cells in three-week-old neonates indicates a persisting difference, or if the number of these cells becomes similar in a short time in breastfed and formula-fed infants. The researcher thinks that the difference probably balances out to a certain extent later, but

the early impacts might still play a crucial role in long-term immune development.

What do these results mean for formula-fed babies? Can it be declared that this phenomenon proves a hindrance for formula-fed babies?

“Scientific results prove that breast milk is more beneficial for the neonate than formula milk in all respects. However, it is not at all rare that a mother can produce little or no milk at all. Therefore, I do not think that formula milk should be excluded from baby care. In particular, special, medicinal formula milk plays an important role. The composition of breast milk is so complex that we still do not understand the full function of each of its components. As a consequence, it is impossible for formula-producing factories to totally copy the composition of breast milk. Mother’s milk contains several cells, including maternal cells and harmless organisms like bacteria as well. All these components might contribute to the healthy development of the infant.”