鈥淭he things that you do in the name of science.鈥� Malcolm Hebblewhite recalls the day he found himself and three colleagues in a darkened lab, stripped to the waist, slathered with ultrasound gel and crowded around a monitor as if they were in a birthing suite. They weren鈥檛 admiring developing fetuses, though 鈥� they were searching for experimental capsules that they had fitted with sensors to sniff out intestinal gases. Each of them had swallowed one of these and was now excitedly watching it wend its way through their gut.
It鈥檚 the kind of work that requires an intrepid spirit 鈥� and a keen sense of humour. 鈥淎 bunch of engineers, developing a product to effectively measure farts. It鈥檚 just the gift that keeps on giving, right?鈥� says Hebblewhite. 鈥淚 mean, the material is endless.鈥�
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But there is a serious side to the work being done at Atmo Biosciences, a medical device company based in Melbourne, Australia. Once dismissed as noxious, antisocial waste, it is now clear that intestinal gases are a vital part of our physiology. A window into the health of our guts, they help govern our gut microbiome, influence our gut function and perhaps even that of other organs too. Knowing more about them could transform our understanding of gut health and debilitating conditions such as irritable bowel syndrome (IBS) and inflammatory bowel disease.
鈥淚 think the revolution is going to come when we can measure these gases well, throughout the gut,鈥� says at Monash University, Australia.
Dynamic gas production
This won鈥檛 be easy. The human gut is several metres long and home to a range of dramatically varying microbial habitats. Yet scientists have largely been confined to collecting samples from either extremity, missing out on most of what happens in the middle. What鈥檚 more, gas production is dynamic, as the microbiome ferments the food its host is eating, and is hugely variable from person to person.
The main gases our microbes produce are hydrogen, carbon dioxide and methane, together with tiny amounts of other gases such as hydrogen sulphide and nitric oxide. Other important molecules are volatile organic compounds like butyrate, which supports gut and . Nitrogen and oxygen from swallowed air are also present and used by gut microbes.
Some gases, known as gasotransmitters, interact directly with our cells and play roles in bodily functions. Methane, for example, slows colon movement and is associated with constipation. Hydrogen sulphide, meanwhile, might smell foul to us, but it plays a key role in and . In high amounts, however, it becomes toxic to cells and may be involved in conditions such as inflammatory bowel disease. But its exact role is unclear and its volatility makes it extraordinarily hard to measure, says Gibson, who is also a consultant for Atmo Biosciences.
What is clear is that changing our diet can alter gas production. Gibson was instrumental in developing the (avoiding foods that contain higher levels of fermentable carbohydrates such as onions, garlic, wheat, rye and barley) to treat irritable bowel syndrome. The idea is that altering the composition of carbohydrates decreases gas production and thus reduces painful distention of the bowel. 鈥淲e鈥檙e trying to work out how we can influence the production of a lot of different gases,鈥� says Gibson. 鈥淭he big problem we have is measuring them.鈥�
Some gases, such as hydrogen and methane, make their way via the bloodstream into the breath, and can be detected there. But this yields no information on where in the gut they are being produced. Other methods involve taking gas samples from faeces, but this doesn鈥檛 capture the full complexity of what鈥檚 happening in the colon.
Some researchers have used catheters to sample gas directly from people鈥檚 rectums, but these often end up contaminated with atmospheric air. 鈥淭here are obvious difficulties in how to collect the samples,鈥� says at the University of Barcelona in Spain. Furthermore, researchers have used a range of different techniques to study the gases they collect. 鈥淭here is a lack of standard methods to do this kind of analysis,鈥� says Marco. This inconsistency means we have little idea what a 鈥渉ealthy鈥� fart consists of.
To tackle this challenge, Marco and his colleague Antonio Pardo turned to a technique called gas chromatography, which allows for very accurate measurements of a gas鈥檚 composition. Working with clinicians, the team recruited five volunteers and built a collector consisting of a catheter plus a small balloon, which was inflated once inside the participant鈥檚 anus to form a seal to stop atmospheric air contaminating the sample. Connected to the catheter was a bag designed to collect gas, and the volunteers were given the rather tricky task of keeping as still as possible for the next few hours while their bags filled up, before the scientists tested the contents in the gas chromatograph.
The team was able to the concentrations of oxygen, nitrogen, carbon dioxide and methane in each sample. To see whether it could be used to measure the effects of diet, the team gave their volunteers food designed to make them fart more (white beans and bananas) or less (a ham and cheese sandwich and orange juice).
The researchers showed that they could distinguish between the two with their gas measurements: the higher flatulence diet led to an increased concentration of CO2 and reduced nitrogen. Their original plan was to study the full molecular complexity of farts, to find new biomarkers for gastrointestinal conditions. Sadly, the project鈥檚 funding dried up before they were able to do this.
We have little idea what a 'healthy' fart consists of
While their method lacks the key advantage of the Atmo capsule 鈥� the ability to sample information all along the gut 鈥� it does offer more accuracy, says Marco. It is an example of the trade-off scientists must currently make when studying the gut.
At present, the Atmo capsule can sniff out hydrogen and CO2 and detect low-oxygen environments that allow anaerobic organisms such as methane-producing microbes to thrive. Also on board are a temperature sensor, relative humidity sensor and an accelerometer. All this shows where the capsule is located in the gut. This can give useful insights: if you know where the capsule is and detect hydrogen, you know there must be microbial activity there 鈥� something that hasn鈥檛 been possible to do up until now, says .
For example, Gibson and his colleagues recently used it to show how changing the kind of fibre in the diets of 20 people with IBS changed the location of , which is known to affect IBS symptoms. It is very early days, but the hope is that the Atmo capsule could eventually help doctors design personalised dietary treatments for people with IBS and other gut conditions.
Wireless fart-sensing
Users simply swallow the capsule, which is about half the length of an AA battery in size, and it makes its way through the gut, while transmitting data wirelessly to a small receiver, worn on a belt outside the body. When it finally reaches the other end, it exits in a bowel movement and is flushed away 鈥� the person does not need to retrieve it. So far, the company has administered more than 1200 capsules in a range of clinical trials, and the device is awaiting approval by the US Food and Drug Administration as an improved way of diagnosing conditions that affect gut motility.
Also in the works are fart-sensing capsules with Bluetooth technology that can pair with a mobile phone app. 鈥淪o you can imagine a scenario where鈥� you purchase a box of capsules, you download the app and you start analysing your own gas composition and motility time,鈥� says Hebblewhite.
Perhaps this will change our attitude to farts 鈥� even make them the subject of dinner party conversation. But in the meantime, if you do feel one brewing, Gibson has some important advice. 鈥淚f you feel like farting, you should,鈥� he says. 鈥淚t鈥檚 not good to retain.鈥�
