Does breast milk prevent food allergies?
20th November 2017 – Could increasing rates of food allergy have been sparked by advice for mums-to-be to avoid certain foods known to be allergenic?
New research suggests that pregnant women might be able to protect their offspring from common food allergies by eating some specific trigger foods such as peanuts and eggs, especially if they go on to breastfeed.
The study, published in the Journal of Experimental Medicine, suggests that minute quantities of foods eaten by the mother can be transferred to her baby in the womb, driving later food tolerance.
So far, the results have only been demonstrated in mice but if shown to be true for humans, could contradict previous advice that mothers should avoid highly allergenic foods, such as peanuts, during pregnancy or while breastfeeding.
Researchers from Boston Children's Hospital Division of Allergy and Immunology and Brigham and Women's Hospital in the US gave pregnant mice allergy-triggering foods.
They found that these foods transferred protective antibodies to their offspring. The antibodies caused the offspring to produce allergen-specific regulatory T immune cells, which helped them tolerate these specific foods.
This protective effect was even greater when the mice were also exposed through breastfeeding, the researchers say.
In other experiments, female mice who had never consumed allergenic foods were given antibodies specific to those foods from other mice. This also resulted in protection for their offspring.
Will it work for people?
Human breast milk, fed to mice whose immune systems had been engineered to respond to human antibodies, also led to protection for baby mice, suggesting that the findings might also apply to human babies.
Mice were chosen because, unlike in human studies, it is easier to control when mother and offspring were first exposed to specific foods.
Now, to explore whether the findings apply to humans, the team is starting to collect breast milk to find out what factors make breast milk protective.
They want to compare milk from mothers whose babies are both at high and low-risk of developing a food allergy. This will be determined by whether they have a sibling with a food allergy or other risk factors, such as a history of early eczema.
They say one key question in why the protective mechanism is not functioning in people who have food allergies.
Commenting on the findings in an email, Professor Mary Fewtrell, a nutrition specialist at the Royal College of Paediatrics and Child Health, says: "The results from this new study are interesting and, although from an animal model, are consistent with current advice that women do not need to avoid allergenic foods while they are pregnant or breastfeeding.
"The latest UK guidance is that parents can introduce allergenic foods to their infant at the same time and in the same way as other complementary foods.
"However, foods such as peanuts must be in an age-appropriate form to avoid being a choking hazard, and parents should seek advice if their infant has had an allergic reaction to a food or has severe eczema."
Editor's note: This article was updated after publication to include comment from the Royal College of Paediatrics and Child Health.