Gut Bacteria May Help Protect Us Against Asthma And Allergy Risk

The microbes that call our guts home may help determine whether or not we develop allergies, suggests a new study published Monday in Nature Medicine.

Researchers at the University of California San Francisco (UCSF) and the Henry Ford Health System in Detroit examined the stool samples of 130 children earlier enrolled in the Wayne County Health, Environment, Allergy and Asthma Longitudinal Study (WHEALS). After conducting a genetic analysis of the samples, collected when the children were one month old, the team found the children had one of three distinct patterns of bacteria and fungi in their guts.

Importantly, these patterns correlated with the likelihood that the children would be later diagnosed with either asthma or allergies at ages 2 and 4. The smallest group, comprised of 11 children, was three times more likely to develop allergies compared to the other two. Those with the healthiest community of gut microbes, or microbiome, also had a greater amount of molecules and cells known to reduce inflammation and regulate the immune system.

"We have been working for over a decade, trying to figure out why some children get asthma and allergies and some don't," said the study's co-senior author Dr. Christine Cole Johnson, chair of public health sciences in the Henry Ford Health System, in a statement. "It seems that the microbial communities within the body could be the keystone to understanding this and a number of different immune diseases."

Dandelion A new study finds that the bacteria we have in our guts as early as one month into life may influence our later risk of developing allergies. Pixabay, Public Domain

In particular, the lowest risk children had higher amounts of certain lipids (fats) that are the theorized food source for T-regulatory cells, presumingly the metabolic byproducts of a healthy microbiome. On the other side, the microbiomes of at-risk children lacked some species of normally seen gut bacteria and had much higher amounts of other fungal species, and their metabolic byproducts contained fats such as 12,13 DIHOME. These chemicals cause the immune system to become hypersensitized and may also reduce the amount of T-regulatory cells, further increasing the risk of allergy, the researchers explained.

While differences in the gut bacteria have been considered a contributing factor for allergies, the study is among the first to examine how they might directly influence our risk. "By focusing on the differences in microbial functions — in their metabolic products and their effects on immune function — this kind of study helps define the pathway we'll need to follow to prevent this disease," said co-senior author Dr. Susan Lynch, an associate professor of medicine at UCSF.

As for why the gut microbiomes of these children were different, the researchers only found two major factors — dog ownership and gender, with boys being more likely to lack a healthy gut. Other research, including by Lynch and her colleagues, has found that the more exposure we have early on to different types of microbes, the better calibrated our immune system becomes.

"Humans have co-evolved with microbes and as a result we rely on their genomes for certain critical functions. We believe this is particularly true during the earliest stages of human development," Lynch said. "But lifestyles have changed dramatically over the past several decades: We've significantly reduced our exposure to these environmental microbes our bodies rely on. Having a dog track the external environment into the home may be just one way to improve the breadth of microbes babies are exposed to in very early life."

Lynch and her team hope their research will not only help pinpoint which children are at risk for developing allergies but someday lead to therapies that can proactively repair their gut microbiomes and eliminate allergies altogether.

Source: Lynch S, Johnson C, et al. Nature Medicine. 2016.

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