Maybe you use an Apple Watch to count your steps or an Oura ring to track your sleep. Or maybe you rely on a glucometer to monitor your sugar levels. We live in an age where access to our health data is unprecedented, thanks to gadgets that digitally monitor our heartbeats, movements and blood. This electronic examination can even extract information from the invisible: our breath.
Today, a handful of at-home tests, like the Trio-Smart or the FoodMarble AIRE, allow consumers to measure the gases escaping with each exhalation.
Molecules in breath can shape a picture of health, transmitting information from the microbes that take up residence in our intestines, says Ali Rezaie, a gastroenterologist at Cedars-Sinai Medical Center in Los Angeles.
But claims that frequent breathalyzer tests can reveal which foods to eat or avoid may be exaggerated. Rezaie advises caution when using such tests to assess food tolerances. “I don’t think that will give you a clear answer,” he said.
Yet there is real science behind breath testing, Rezaie says. In clinical settings, they can help doctors detect gastrointestinal disorders. And respiratory molecules could one day serve as warning signals for infections or diseases like asthma.
Microbes produce gas in our intestines
Our intestines contain a wonderful world of microbes. Bacteria, archaea and fungi can all coexist in a diverse community of microscopic life – and many even do us good. They help break down food, strengthen our gut barrier, and produce compounds used by our bodies, says Andrew Kau, an allergist-immunologist at Washington University in St. Louis. “They have very diverse effects on human health,” he says.
Sometimes, however, these effects can become harmful. In people with small intestinal bacterial overgrowth, or SIBO, bacteria that typically reside in the colon travel up into the intestines to grow where they shouldn’t. “This means there are extra bacteria in your small intestine,” says Rezaie. More bacteria means more microbial digestion of the foods we eat, which “can produce a lot of gas.”
Doctors can test for SIBO by measuring gases like hydrogen and methane in the breath, but it takes more than a single puff. Before the test, patients must eat a bland, low-fiber diet and then fast overnight. At the clinic, they will blow into a breathalyzer that analyzes the captured gases. Then, patients consume a sugar solution and blow again every 15 minutes for the next two hours.
It is a complex process that doctors have standardized to determine if a patient’s gas levels are out of balance. Running such tests at home can be a bit tricky, Rezaie says. The machine used by his team is calibrated twice a day to ensure the accuracy of the measurements. That’s why, if patients can’t see an expert, he prefers commercial home systems in which users collect their breath and send it to a lab. Devices that do all this at home may be less accurate.
And while gases like hydrogen and methane can give some insight into what’s happening in the gut, they’re only the start of what our exhales can reveal.
Microbial signatures float on breathing
Every time we exhale, we release hundreds of complex chemicals called volatile organic compounds. Think of them as a scent, says Audrey John, a pediatric infectious disease specialist at Children’s Hospital of Philadelphia. If you poured perfume on a table, it would evaporate and the scent molecules would disappear into the air.
This year, Kau and John showed that these types of molecules can serve as signatures for specific gut microbes. Scientists had hypothesized that some of the volatile organic compounds circulating in our breath might come from our microbiomes, but no one was sure. This is a difficult question to answer because volatile organic compounds are everywhere: emitted by our foods, given off by our mattresses, and released by our own fabrics.
Kau’s team found that mice with microbiomes had a different set of volatile organic compounds in their breath than those without them. And when the team transplanted microbiomes into germ-free mice, the animals’ respiratory compounds changed. They now resembled those emitted by animals carrying the original microbiome, Kau and John reported in Cellular metabolism. It is evidence that gut microbes cause the differences seen in these types of respiratory compoundsyou say.
Researchers wondered whether respiratory compounds could signal the presence of disease-related gut microbes. In a clinical study of 41 children, children with asthma had different respiratory compound signatures than children without the condition, researchers found. They linked these signatures to the amount of Eubacterium siraeum, a bacteria previously linked to pediatric asthma, in children’s stools.
Breathalyzer technology isn’t ready for prime time, John says. This would require a much larger study to validate the results. In the meantime, she wants to use breathing to detect sepsis in the newborn, a potentially fatal condition that can result from infection. People like John could then identify at-risk infants and intervene before they get sick. “For me,” she said, “that would be a really profound result. »