Researchers say a high-fiber diet during pregnancy may prevent offspring from developing asthma.
Led by Dr. Alison Thorburn, of the Department of Immunology at Monash University in Australia, the study suggests a high-fiber diet alters a mother's gut bacteria during pregnancy, producing anti-inflammatory substances that suppress asthma-related genes in offspring.
This is not the first to study to associate a high-fiber diet with reduced asthma risk. In January 2014, Medical News Today reported on a study in which researchers found mice fed a high-fiber diet had reduced reactions to asthma-inducing allergens, compared with mice fed a low-fiber diet.
For their study, Dr. Thorburn and colleagues set out to determine whether a high-fiber diet consumed during pregnancy could impact offspring's risk for asthma development.
To reach their findings, the team fed pregnant mice one of three diets during their third trimester: a high-fiber diet, a moderate-fiber diet or a low-fiber diet.
When the offspring of the mice were adults, they were exposed to house dust mites - a trigger for asthma in humans.
Metabolites produced by fiber digestion suppressed asthma-associated genes in offspring
The researchers found that the offspring of mice whose mothers were fed a high-fiber diet during pregnancy did not develop asthma-like symptoms, while the offspring whose mothers were fed a low-fiber diet did.
Further investigation revealed that the pregnant mice fed a high-fiber diet experienced changes in gut bacteria; they possessed specific microbes that produced anti-inflammatory metabolites when the fiber was digested. These metabolites circulated the bloodstream and traveled through the uterus to the fetus, suppressing Foxp3 genes linked to asthma development.
The researchers wanted to see whether a maternal high-fiber diet in humans would have the same effect on offspring. They did so by analyzing the blood samples and diet data of 40 pregnant women, as well as data detailing the frequency of doctor's visits due to respiratory symptoms in their offspring during the first year of life.
The team found women who consumed a high-fiber diet during pregnancy also had anti-inflammatory metabolites present in their blood, and the offspring of these women were significantly less likely to have visited the doctor two or more times as a result of respiratory complaints in their first year of life.
Commenting on their findings, the researchers say:
"High fiber [...] suppresses expression of certain genes in the mouse fetal lung linked to both human asthma and mouse AAD [allergic airway disease]. Thus, diet acting on the gut microbiota profoundly influences airway responses, and may represent an approach to prevent asthma, including during pregnancy."
In addition, the team says their findings may explain why children who grow up on a farm appear to be at lower asthma risk.
"We speculate [this] may relate to dietary differences between rural and urban settings," they explain, "or may relate to microbes encountered in the farm environment that are geared for high SCFA [short-chain fatty acid] production (that is, feces from livestock that mostly digest fiber)."