Education and outreach

Inside the microbiome: why good gut bacteria is the big hope for allergic disease

Pioneering researchers are finding astonishing evidence that tiny gut microbes may hold the key to preventing – or even curing – asthma and food allergies. Here’s why they say it’s time we learn to love our bacteria.

Microbes exist everywhere – in water, air, soil, plants and animals, and from the coldest regions of the Antarctic to the boiling hydrothermal vents at the bottom of the sea. According to microbiologist Brett Finlay, there are far more bacteria on Earth than there are stars in the sky, and despite their microscopic size, the Earth’s microbes weigh more than all plants and animals combined. They also predate all other life on Earth.

If you think you can escape microbes in your own life, think again: the human body contains trillions of bacterial cells – most of which reside in your gut. For every one of your human genes, there are roughly 100 bacterial genes; some estimates are as high as 500.

But researchers around the globe say these bugs aren’t something to be feared. In fact, they are finding striking evidence that these personal ecosystems may help to solve the mystery of the rapid rise of multiple diseases, including asthma and food allergies.

For almost three decades, a growing body of research has linked the sharp increases in asthma and allergy rates to “the hygiene hypothesis” – the idea that our urban living environments have become too sterile and germ-free, leading our immune systems to become misguided and reactive.

Now, in some of the biggest advances the field of allergy medicine has seen, scientists are beginning to zero in on exactly what’s happening – and they’re banking on those teeming, minuscule microbes to lead a health revolution that could prevent, and possibly even cure, allergies and asthma.

Collectively, those microbes are known as the human microbiome. This is a field showing so much promise that in 2016, the U.S. government and private industry proposed the National Microbiome Initiative – a half-billion-dollar effort to study the vast microbial systems on Earth, and in the human body.

For Finlay, co-author of the book Let Them Eat Dirt: Saving Your Child from an Oversanitized World, uncovering a major piece of the puzzle began in 2007 with a passing conversation over dinner with his wife. The acclaimed University of British Columbia microbiologist had spent his life studying “bad” gut bacteria such as E.coli and salmonella.

As an experiment, his team began feeding antibiotics to mice to find out which microbes were affected. At dinner his wife, who is a pediatric infectious disease specialist, pointed out that children who get antibiotics in the first year of life have higher rates of asthma.

“I thought that was a bit strange, because asthma is a lung disease and we were talking about gut microbes,” he recalls with a laugh. “What do antibiotics have to do with anything?” Still, Finlay checked the research, and found several studies that linked antibiotics and asthma.

Intrigued, he set up an experiment: feed different antibiotics that only act in the gut to germ-free mice, and find out if their asthma rates are affected. With some of the antibiotics, the effect was drastic. “We saw a profound asthmatic reaction,” says Finlay, sitting in his sunny office on the UBC campus. “It was just off the charts. It was really surprising, because we hadn’t done anything other than treat these mice with antibiotics.”

What came next was even more exciting. In 2009, Finlay teamed up with Dr. Stuart Turvey, a pediatrician who specializes in allergy and immunology and is one of the co-leaders of the Canadian Healthy Infant Longitudinal Development (CHILD) study, which is following 3,500 children in hopes of pinpointing the root causes of allergy and asthma.

As part of the study, stool samples were collected from kids at birth, three months of age and one year. As the kids grew and some began to develop asthma, the researchers looked back to those frozen early stool samples to see if there was something different in the microbial makeup. Sure enough there was and it came down to four bacteria: Faecalibacterium, Lachnospira, Veillonella, and Rothia, which the scientists dubbed “FLVR” (pronounced “flavor”).

“Basically, at three months of age, if you had these four microbes, you had a very low risk of asthma,” explains Finlay. “If you had lower levels of these four microbes, you were in the high-risk group.” The team then took the research a step further, and orally administered those microbes into “germ-free” mice – that is, mice that have no microbes. Mice that received the FLVR microbes had markedly lower levels of lung inflammation and signs of asthma than those that did not.

“We were able to show that if we deliberately gave back the FLVR bacteria, we could protect baby mice from asthma, proving that these bacteria had some functional and protective role,” says Turvey.

“It opens the door for a way to maybe prevent asthma. That’s the Holy Grail,” explains Turvey, while acknowledging this quest still requires a lot of work. “The vision might be for safe versions of the FLVR bacteria that could be given to children early in life to help establish the right microbiome bacterial community, which would help protect them from developing asthma. That’s a huge paradigm change.”

Read full article on Allergic Living.