Evidence is overwhelming that city kids are much more likely to develop allergies than children in rural communities. The notable difference between these kids’ immune systems has given rise to lot’s of theories but new data sheds light on possible reason why – their immune systems may mature faster, and breast milk appears to play an important supporting role.
The study, led by researchers from the University of Rochester Medical Center, compared infants from Old Order Mennonite (OOM) farming families in New York’s Finger Lakes region with urban and suburban families in Rochester, researchers found that farm-exposed babies had more “experienced” B cells and higher levels of protective antibodies during the first year of life.
“What this study shows is that their B cell and antibody responses are essentially ahead of schedule compared to urban infants,” explains lead study author Kirsi Järvinen-Seppo, MD, PhD. “Their immune systems seem better equipped, earlier in life, to handle foods and other exposures without overreacting.”
For the new study, researchers compared 78 mother/child pairs from the Old Order Mennonite community with 79 moms and kids from urban and suburban Rochester. They followed the mothers and children through the first year of life, collecting blood, stool, saliva, and human milk samples.
According to the researchers, the rural kids are getting their more mature antibodies from their mothers’ milk. Not only did the farm babies have higher levels of immune cells, higher levels of antibodies were also found in human milk samples.
The research team then took a closer look at egg allergies, one of the most common food allergies in young children. Farm children had higher levels of egg-specific antibodies in their blood, and mothers had higher levels of egg-specific antibodies in their breast milk, the study found. Meanwhile, Rochester babies had varying levels of egg-specific antibodies in their blood, and this was linked to their risk for egg allergy. The more antibodies, the lower their risk of egg allergy.
The researchers say the Mennonite moms likely have more of these egg-specific antibodies thanks to their diet. Old Order Mennonite families typically raise their own chickens and eat a lot of eggs. That repeated exposure seems to boost mothers’ antibody levels against egg proteins, and they pass that protection on to their children through breast milk.
Mennonite infants were also born with higher cord blood levels of antibodies to dust mites and horses, reflecting the environmental allergens to which their moms are regularly exposed, researchers said. But Rochester babies had higher levels of antibodies to peanuts and cats, reflecting the more common allergen exposures of suburban and urban moms.
The researchers say their results may explain why breastfeeding has not been consistently linked to a lower risk of food allergies – because it depends on what the mother is eating. However, mothers’ milk likely isn’t the only reason why farm kids have fewer allergies, Järvinen-Seppo said.
Daily exposure to farm animals and germs, drinking well water, less use of antibiotics and distinctly different patterns of gut bacteria all have been previously shown to also help shape the allergy resistance of rural children, researchers said.
They’re now conducting a clinical trial involving expecting mothers who will be assigned to either eat or avoid egg and peanut during late pregnancy and early breastfeeding. The team then will compare mothers’ antibody levels and their kids’ development of food allergies. The results could solidify the theory that mothers’ diets during pregnancy and breastfeeding can add another layer of protection through the antibodies they pass to their babies. (Source: SOURCES: University of Rochester, Science Translational Medicine)
