Scientists have found a way to predict whether babies will develop asthma or allergies

Bundles of joy—and microbes.
Bundles of joy—and microbes.
Image: Reuters/Michaela Rehle
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For a while now, it’s been clear to scientists that the collection of bacteria that dwells in our digestive tract plays a part in the way we break down food, respond to infections, and even our moods. But these associations have, so far, been just links, and not predictors.

Now, though, scientists have found that a particular pattern characterized by a lack of bacterial diversity in a baby’s gut microbiome can help predict whether or not she develops asthma or allergies later in life. Researchers led by a team from the University of California San Francisco (UCSF) found that infants with less bacteria and more fungi (a smaller component of the overall gut flora) made them three times more likely to develop allergies and asthma than their peers. Their work was published (paywall) in Nature Medicine on Sept. 12.

We have a reciprocal relationship with the tiny organisms that live in our guts. Lots of things that we do (or that happen to us) throughout our lives—like being born vaginally, having dogs (paywall), and eating a high-fiber diets—can increase the number of types of these benign microscopic organisms, and that’s widely considered a good thing: Having more diverse microbiomes has been associated with lower risks for conditions like obesity, auto-immune disease, allergies, and asthma. Researchers think that if they can spot these particular gut microbial populations early on, they can develop treatments, like diet or lifestyle changes, to alter these populations before chronic conditions become a problem.

In 2003, researchers from the Henry Ford Health Center in Detroit, Michigan took soiled diapers from 130 one-month old infants living in the area and froze them. Ten years later, when technology had sufficiently advanced, the Michigan team sent the samples to researchers at UCSF, who collected detailed sequences of the microbial genetic information. The UCSF researchers also looked at the collection of other molecules generated by these microbes.

Meanwhile, when the babies reached two and four years old, researchers tested them to see if they had risk markers for asthma and severe allergies. They found that 11 of the 130 babies they sampled were missing certain types of gut bacteria and had higher concentrations of fungi. This combination led to fewer immune cells that stop allergic reactions, and more chemical markers that have been associated with asthma.

Susan Lynch, a gastroenterologist at UCSF and lead author of the paper, said in a press release that this fraction of babies with less-diverse bacteria and a larger fungal population is similar to the proportion of the adults with severe allergies or asthma. Although the scientists aren’t sure exactly how best to diversify the gut microbiomes of babies, their work suggests that there are some steps parents can try to decrease the risk of these conditions, like owning a pet. “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,” she said.