Study shows breastfed infants have higher tolerance for stress

A study published this month illustrates a biological link between breastfeeding a mother and other behaviors that nourish her baby's health. The study showed that breastfeeding was associated with increased stress tolerance, as indicated by differences in levels of cortisol, a stress response hormone. In addition, a second biomarker used consisted of DNA samples from oral cells or cheek samples, which showed the degree of suppression of stress-related genes.

The study is the first to replicate animal studies on the incidence of mother-child behavior on child health with human participants, said Barry Lester, professor of psychiatry and pediatrics and lead author of the study. Previous studies have been done only on rodents, he added. Given the way in which the results of animal studies apply to human studies, "if this were true in humans, the implications are enormous," said Lester.

The study divided the mother-child pairs into two groups: one group of breastfed infants and another group. Infants who have been breastfed have seen lower levels of DNA methylation – a process that suppresses genes – of stress-related genes, such as NR3C1.

"You can have a methylation test comparable to a blood test that can determine your methylation," Lester said. "If moms are depressed during pregnancy, the fetus has also increased the methylation of NR3C1 and (cortisol is) more reactive at birth." But there is still no biomarker available for screening or treatment, he added.

The study "demonstrates the importance of supporting the caregivers' early living environment and the critical importance of helping children develop appropriate stress response systems … and coping patterns," said Elizabeth Conradt, Assistant Professor of Developmental Psychology at the University of Utah and author of the study. Conradt also acknowledged that breastfeeding may not always be possible. "Breastfeeding poses many challenges and we should not assume that all parents are able to do so," she said.

Lester and Conradt agreed on the need for follow-up studies to replicate these results. "The size of the sample was less than ideal," said Conradt. "We plan to carry out a replication study (at the University of Utah), … and we also hope to see longitudinal studies."

"In the future, we will be able to … examine other markers and behavioral parameters," said Todd Levine, an associate clinical professor in psychiatry and human behavior, not associated with the study. Overall, the study has "strong implications for how we raise children," Levine added.

Research is "a source of pride" for the hospital, he said.