A Pregnant Woman's Diet Could Affect Her Baby's Gut Bacteria, Study Suggests

A mother's diet could affect the genetic makeup of the community of organisms in and on her baby's body. Getty Images

What an expectant mother eats during pregnancy could change the bacteria that populate her baby's gut, according to research.

The study adds to a growing body of evidence offering insight into the microbiome: the name given to the genetic makeup of the microbes that populate the inside and outside of our bodies. Most of these estimated 100 trillion microbes live in our guts, and scientists believe they play an important role in our overall health and the risk of developing diseases.

The bacteria that constitute a baby's gut microbiome, therefore, are important for the development of their immune system and overall health. The authors of the study published it in the journal Microbiome.

To shed light on the potential link between a mother's diet and her baby's gut microbiome, researchers at Dartmouth-Hitchcock Medical Center in New Hampshire recruited 145 six-week-old babies and their mothers.

Over a 6-week period, stool samples were collected from the infants to reveal the bacteria living in their digestive systems. The mothers, aged around 32 years old on average, documented their individual diets in a questionnaire. Most were first-time mothers. Factors that can affect an individual's microbiome were also noted. These included the fact that 66 percent of the children were born vaginally; a further 70 percent were breastfed at six weeks of age; and the majority of the children hadn't attended daycare or taken antibiotics.

The tests revealed the babies' gut microbiome was largely constituted of four types of bacteria: around 20 percent Enterobactericeae, almost 19 percent Bifidobacterium, just over 10 percent Bacteroides (10.44%) and around 8 percent Streptococcus.

Asked if any of the microbes identifed are more beneficial than others, or even harmful, Dr. Anne G. Hoen, study author and assistant professor of microbiology and immunology at Dartmouth Geisel School of Medicine, told Newsweek: "The microbiota identified in the infants in our study are normal inhabitants of the human intestinal tract.

"Bifidobacterium, Clostridium, and Bacteroides, which respectively characterize the three infant gut microbiome clusters we observed, have all been studied for their beneficial roles in the infant gut."

The researchers then categorized the babies according to the bacteria most abundant in their gut. As evidence suggests babies encounter different bacteria when they are born vaginally than via c-section, the latter were placed in their own group.

Sara Lundgren, lead author of the study, explained in a statement: "We expected results to differ based on delivery mode, but we were surprised to find that the abundances of some microbes were increased in association with maternal intake of a food group in one delivery mode group, but decreased in the other delivery mode group."

Women who ate more fruit than other participants were more likely to have babies with higher levels of Streptococcus and Clostridium bacteria, but less Bifidobacterium. Meanwhile, Bifidobacterium was higher in mothers who ate more red and processed meat. Mothers who delivered babies via c-section had higher levels of Streptococcus and Clostridium if they consumed more dairy products than others. The authors suggested this could explain why infants born by c-section are at greater risk of dairy allergies.

The authors acknowledged the women were drawn from northern New England and were therefore a relatively homogenous cohort, which could present problems in how the study translates to a wider population.

"Some of the effect of maternal diet we observed may be due to differences in composition of breast milk that infants consume," Lundgren told Newsweek. "Over 70 percent of infants in our study were exclusively breastfed and only 4 percent were exclusively formula fed, so the extent to which maternal diet in pregnancy affects the gut microbiota in infants who are formula fed is unclear."

Researchers hope their work could be part of the basis for updated dietary recommendations for pregnant and breastfeeding women, said Lundgren.

Previous studies have suggested the Mediterranean diet, for instance, can prevent a child's risk of wheezing, while a diet high in meat can increase the risk, the authors stated.

This article has been updated with comment from Dr. Anne G. Hoen and Sara Lundgren.