Breastfed babies are believed to have fewer allergic conditions, such as eczema and food allergies, than formula-fed babies; yet the reason has not been fully understood. Now, a new study from Penn State College of Medicine reveals that small molecules found in most humans’ breast milk may reduce the likelihood of infants developing allergic conditions such as atopic dermatitis and food allergies. The researchers said the finding could lead to strategies for mothers – such as encouraging and supporting breastfeeding or dietary and physical interventions – to help reduce the risk of their babies developing allergies.
Atopic conditions, such as food allergies, asthma, and a skin condition called atopic dermatitis occur in about one-third of children due to inappropriate activation of the immune system from environmental exposures.
“Infants who breastfeed beyond three months may have a lower risk of these conditions, but we don’t fully understand the biology behind this,” said Dr. Steven Hicks, associate professor of pediatrics and pediatrician at Penn State Health. Children’s Hospital.
Hicks’ research focuses on the relationship between environment, biology, and neurodevelopment and growth in children. His previous studies demonstrate how micro-ribonucleic acids (miRNAs), tiny molecules that can regulate gene expression throughout the body, can be used to diagnose certain health conditions like concussions or autism.
“There are nearly 1,000 different types of miRNAs in human breast milk, and their composition varies due to maternal characteristics such as weight, diet, and genetics,” Hicks said. “We hypothesized that four of these miRNAs may be protective against childhood allergies based on previous research showing relationships between these miRNAs and certain allergic conditions.”
The researchers followed 163 mothers who planned to breastfeed for at least four months and their babies from birth to 12 months. They tracked how long each baby was breastfeeding and measured the miRNA composition of each mother’s breast milk during lactation (0, 4 and 16 weeks). The team calculated the amount of specific miRNAs consumed by infants based on reported breastfeeding patterns and the concentration of certain miRNAs in breast milk samples. The researchers assessed the infants for atopic dermatitis, food allergies and wheezing throughout the study.
Of the infants studied, 41 (25%) developed atopic dermatitis, 33 (20%) developed a food allergy, and 10 (6%) experienced wheezing. Infants who did not develop atopy consumed, on average, greater amounts of miRNA-375-3p (miR-375) in their mother’s breast milk than infants who developed atopy. There were no other differences in maternal traits, childhood traits, or environmental exposures between atopic and nonatopic infants. The researchers also found that levels of this miRNA increased throughout lactation and that mothers with a lower body mass index tended to have a higher concentration of miR-375. The results were published in The American Journal of Clinical Nutrition September 27.
“The fact that miR-375 content increased during lactation may explain why sustained breastfeeding has been associated with reduced atopy in some studies,” Hicks said. He noted that the largest increase in miR-375 occurred during the first month after birth, but the upward trend continued between the first and fourth months. “Unlike formula, which contains no human miRNAs, miR-375 is present in over 99% of breast milk samples, and it accounts for just under 1% of all miRNAs in breast milk.”
According to Hicks, the results of this study could lead to new interventions to help prevent infants from developing allergies. Future research will focus on confirming these findings, defining the mechanisms by which miR-375 prevents allergies, and exploring interventions to increase miR-375 levels in breast milk. Hicks also said that with further research, miR-375 could one day be added to formula, which currently contains no miRNAs, to help address the disparity that formula-fed babies are more likely to develop atopic conditions.
Ramin Beheshti, Desirae Chandran, Kaitlyn Warren and Alexandra Confair of Penn State College of Medicine also contributed to this study. The researchers declare no related conflicts of interest.
This study was supported by a grant from the Gerber Foundation. The opinions expressed are solely those of the authors and do not necessarily represent the views of the Gerber Foundation.
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Material provided by Penn State. Original written by Zachary Sweger. Note: Content may be edited for style and length.