In the magic formula of breast milk there are 700 species of bacteria
17/01/2013
Study on Spanish mothers shows that bacteria in milk are different if women are overweight or have a scheduled cesarean section. This flora may be important for the baby's immune system.
Hundreds of millions of years of evolution are concentrated in the first food of any mammal. Now, it is known that the complexity of breast milk involves yet another factor. When a human baby drinks colostrum for the first time, the milk that the mother produces immediately after giving birth, she is taking into her mouth more than 700 different species of bacteria that will forever define the flora of her digestive tract, reveals a study recently published in the American Journal of Clinical Nutrition.
Milk is a food that is adapted to the species. In kangaroos, where development outside the placenta begins earlier, the composition of the milk changes as the baby, in its mother's pouch, grows and develops its brain, nails and fur. And when two breasts are used by kangaroos of different ages, the milk from each is suitable for each of them.
In developing countries, in the first six months of a baby's life, breastfeeding increases the chance of survival six times and prevents diarrhea and lung infections. "Breast milk provides the nutrients, vitamins and minerals a child needs in the first six months and also the mother's antibodies that help fight diseases", reads the UNICEF website.
It was only recently discovered that there are bacteria in breast milk, but its characteristics continue to surprise. A Spanish team has now analyzed, at three different times, the bacteria in the milk that 18 women produced after having children: at birth, one month and six months later. Molecular techniques made it possible to identify the bacteria present in greater and lesser quantities.
The team discovered that colostrum has more than 700 different species and is dominated by lactic acid bacteria of the genus of Weisella and of Leuconostoce by others such as Staphylococcus, Streptococcus and Lactococcus. After one month and six months, what comes to dominate are typical genera of the oral cavity: Veillonella, Leptotrichia and Provetella.
But what role will they have? "Perhaps the bacteria in breast milk are immune stimulators to recognize specific bacteria and to fight against others", Alex Mira and María Carmen Collado, two of the authors of the article who belong, respectively, to the Institute of Agrochemistry and Food Technology, of the Spanish Superior Council for Scientific Research, and the Superior Center for Public Health Research, in Valencia, responded to PÚBLICO via email. "If this is true, the maternal immune system can regulate the bacteria to which the baby is exposed in a timely manner and the lack of this modulation could have important consequences for the development of the child's microbial flora and the maturation of their immune system."
Internal route of transmission
When researchers compared the bacteria in the milk of normal-weight and obese women, they noticed an important difference in composition. Bacteria in the milk of obese women were less diverse. This change may be an "additional mechanism that explains the greater risk of obesity in children of obese mothers", the article reads.
Another surprise was the bacterial composition of the milk of mothers who had a scheduled cesarean section, in relation to mothers who had a natural birth or who, during childbirth, were forced to have a cesarean section. The bacteria in the milk were different and less diverse. "This could have consequences for allergies, asthma and other diseases influenced by a deficient immune response", say the two authors.
No one yet knows for sure how bacteria appear in milk. The team analyzed the bacterial composition of the skin of mothers and babies, the mothers' digestive system, the vaginal flora, but the composition of the milk is unique. It is assumed that it is through an internal route, controlled by the immune system, that specific bacteria from the digestive tract reach the milk. This transmission can be influenced by physiological stress and the hormonal discharge of childbirth, since in unscheduled cesarean sections the bacterial composition of the mother's milk is similar to that of the milk of women who had a natural birth.