Drinking Milk While Breast-Feeding May Reduce Kids’ Food Allergy Risk

Children of mothers who drink relatively more cow's milk during breast-feeding are at reduced risk of developing food allergies. That is the conclusion of researchers from Chalmers University of Technology, Sweden, in a new study published in the scientific journal Nutrients.

The result is based on a survey of more than 500 Swedish women's eating habits and the prevalence of allergies in their children at 1 year of age.

"We have found that mothers of healthy 1-year-olds consumed more cow's milk during breast-feeding than mothers of allergic 1-year-olds. Though the association is clear, we do not claim that drinking cow's milk would be a general cure for food allergies." says Mia Stråvik, a doctoral student in the division of food science at Chalmers University of Technology, and first author of the study.

There are many factors behind the risk of food allergy, not least genetic predisposition. Yet, as Stråvik explains, "Diet is a factor where parents themselves can have direct influence. It is quite common nowadays for young women to avoid drinking milk, due in part to prevailing trends and concerns, some of which are linked to myths about diet."

According to Ann-Sofie Sandberg, PhD, Stråvik's supervisor and a professor at Chalmers, one possible explanation may be that the milk in the mother's diet contains substances that stimulate the maturity of the immune system.

"In a child's early development, there is a time window where stimulation of the immune system is necessary for the child to develop tolerance to different foods."

According to something known as the hygiene hypothesis, early contact with various microorganisms can function as something of a “kickstart” for a child's immune system, Sandberg explains.

"But, with the lower prevalence of microorganisms nowadays in our more hygienic society, substances taken in through the mother's diet can be another way to stimulate the maturity of the immune system."

Stråvik's study isn’t the first to link cow's milk in a mother's diet to a reduced risk of allergies in children. Previous studies, however, have often been based solely on questionnaire responses—both in terms of eating habits and the presence of allergies. In this study, both data and conclusions are significantly more robust.

"In this study, we were able to actually verify the women's reported intake of milk and milk products through biomarkers in her blood and breastmilk. The biomarkers are two fatty acids formed in the cow's stomach, which are specific to dairy products," Stråvik says. "Furthermore, all the cases of allergy in children were diagnosed by a doctor specializing in child allergies."

The study is part of a more extensive research project built around a family cohort study of 655 families who gave birth at Sunderby Hospital near Luleå, northern Sweden, during the years 2015–2018. The current study is the first scientific publication, focusing mainly on allergies based on data collected from the families in northern Sweden.

The mothers in the study, more than 500, gave detailed accounts of their eating habits on three occasions—in the 34th week of the pregnancy, one month after the birth, and four months after birth. At 1 year of age, the children were medically examined and all cases of food allergy, atopic eczema, and asthma were identified.

After the material was adjusted for various other factors, such as hereditary predisposition or reverse causation, the researchers were able to establish that there was indeed a clear connection between the mother's intake of milk and dairy products and the smaller incidence of food allergy in their children.

"No matter how we looked at and interpreted the data, we came to the same conclusion," states Chalmers researcher and coauthor Malin Barman, MSc, assistant supervisor to Stråvik."The mechanisms behind why milk has this preventative effect against allergies, however, are still unclear." A further explanation of various hypotheses can be found below.

Another result in the study that Stråvik highlights is that children of breast-feeding mothers, who at the four month measurement were eating a lot of fruit and berries, tended to suffer from eczema to a much greater extent—though she stresses that further studies are needed before anything can be said with certainty about this connection.

A follow-up study is currently underway to examine the children's health at age 4.

— Source: Chalmers University of Technology