Breastmilk gives babies weapons against viruses
Elusive proof that mothers give their babies an immune response to viral illnesses through breast milk - even when the mother isn't sick herself - has been found by an Australian researcher.
The work, part of the doctoral thesis by Dani-Louise Bryan of the Paediatrics and Child Health department of Flinders University in Adelaide, found that mothers produce antibodies in breast milk if they are exposed to pathogens their babies encounter, regardless of whether they display any symptoms of disease.
"What we were looking at was [whether] exposure to a viral antigen causes a feedback response in the mother to the infant being ill," Bryan told ABC Science Online.
The research concentrated on a common virus in childhood, RSV (respiratory syncytial virus). "It is one of the most common respiratory pathogens of infancy, and the majority of infants will be infected with it in their first 12 months of life," said Bryan. "In a significant proportion of those, it develops into a very severe bronchiolitis which requires hospitalisation."
The research targeted the mothers of hospitalised infants, requesting breast milk from them. They then compared it to the milk of healthy mothers in the general community, looking at a number of different factors in their milk. All the babies in the study were exclusively breastfed.
In the breast milk of mothers with sick babies, Bryan found a four- to five-fold increase in the total number of white blood cells - which help protect against viral and bacterial infections - compared to the healthy control mothers.
"Obviously, there is some type of feedback in the mums being exposed to the virus," said Bryan. "The mum didn't need to be suffering from the virus, but the feedback is still strong enough that the milk was changing to help the baby."
Although the research found a link, more work needs to be done to understand what the immune cells are doing in the infant once they have been passed through the milk.
There is little doubt that babies benefit greatly from being breastfed, but the majority of research into the area has used epidemiological studies, she said. Scientific literature on the topic spans hundreds of years and shows that breastfed babies suffer fewer illnesses. But evidence that breast milk provides an immune response to viral infections is rare.
"The evidence for this has been severely lacking," said Bryan, who is currently preparing a paper, which she and her colleagues will be submitting to a leading journal.
She suggested her finding could help back arguments for the 'hygiene hypothesis': that children should be exposed to dirt and diseases in childhood to allow their immune system to strengthen. In this case, it is the mother that needs to be exposed to the diseases.
"Babies need to be exposed to different bugs, but if mum is also exposed to bugs it can change her milk," Bryan said. "This is the loop of the mother-infant interaction. Breastfed babies are not an immunological island."