When Summer Walker started looking into why so many Australian babies develop food allergies, she stumbled onto something surprising: a common kitchen ingredient might help.
New research from The Kids Research Institute Australia found that pregnant women who took prebiotics—found naturally in foods like garlic, leeks, and onions—while receiving antibiotics had babies with no increased food allergy risk. But babies born to mothers who received antibiotics without prebiotics were more than five times as likely to develop a food allergy in their first year of life.
"This is a really important finding for families," said Walker, a research assistant at The Kids Research Institute Australia and lead author of the study, published in the journal Allergy.
The study followed 652 pregnant women and their babies in Western Australia as part of a trial called SYMBA. Most of the participants came from ORIGINS, Australia's largest birth cohort study. Women in the study took either a prebiotic supplement or a placebo from mid-pregnancy until their baby turned six months old. All babies in the study had a family history of allergic disease, putting them at higher risk.
During the study, more than 80 percent of mothers and 20 percent of babies received antibiotics. Antibiotics are often essential during labor and save lives—but researchers have increasingly worried about their effects on a baby's developing immune system. Walker explained that antibiotics don't just target harmful bacteria; they also wipe out the healthy gut bacteria that help train the immune system to tell the difference between safe foods and dangerous threats.
"During pregnancy, this can potentially result in long-term child health effects," Walker said.
Prebiotics work differently. They're a type of fiber that feeds the good bacteria already living in the gut, helping them grow and thrive. Think of it like giving your garden the right fertilizer—healthy gut bacteria bloom, and they may help keep the immune system balanced.
The research found that antibiotics taken during labor had the strongest effect. These drugs peak in the umbilical cord within 30 minutes and can stay active in a baby's system for hours, giving them more time to disrupt the infant microbiome. Previous studies often grouped all antibiotics together, but this research looked at birth-related antibiotics separately, making the link clearer.
Around one in four Australian mothers receive antibiotics during pregnancy, and up to half of all infants receive antibiotics in their first year of life. That means a simple dietary change could potentially help a lot of families.
Walker is quick to note that more research is needed. But she says the findings open the door to exploring whether prebiotics might protect against other child health conditions linked to antibiotics. In the meantime, she recommends that pregnant women follow existing dietary advice and talk to their healthcare provider before starting any new supplements.
The good news? You don't necessarily need a pill. Mediterranean-style diets—rich in garlic, leeks, onions, asparagus, and legumes—are naturally packed with prebiotics, and they're already recommended for many expecting mothers anyway.