Human Life Is a Gas

Illustration: RMIT University

Changes in production of certain gases in the human gut have been linked to gastrointestinal disorders including painful constipation, irritable bowl syndrome (IBS), and colon cancer. Yet how and why this happens is not well understood. Without resorting to stressful invasive means, measuring and tracking gas concentrations in our stomachs and small and large intestines has to date been impractical.

That’s about to change. Researchers at RMIT University in Melbourne, Australia, have designed and custom-manufactured indigestible capsules that can measure the concentration of different gases during digestion in the gut of animals and humans—a world’s first, they claim. The capsules meet the standards necessary for such testing, and after conducting a series of trials on pigs, the researchers have begun recruiting human volunteers on which to test the next version of the pill.

An electronic capsule is composed of: an indigestible cladding; a gas-permeable membrane covering a sensor for detecting hydrogen, methane or carbon dioxide; a microcontroller; a 433-megahertz wireless transmitter; and four silver oxide batteries. The latest version of the capsule measures just 2.6 by 1.1 centimeters, which is “about the size of a 000 fish-oil capsule,” lead researcher Kourosh Kalantar-zadeh, a professor at RMIT’s Centre for Advanced Electronics and Sensors, told IEEE Spectrum.

“Nothing in the capsules is really expensive,” he added. “The batteries cost around $5 or $6 in total, as does the thermal-conductivity sensor, while the microcontroller is only 50 cents. We estimate the materials cost at $15, depending on component prices. This would come down with large scale production.”

The sensor data is transmitted straight from the gut to a custom-made coder-decoder unit that can be clipped onto a cellphone. The processed data is then sent to the phone for viewing via Bluetooth.

In one of the first animal trials, pigs—which have similar digestive systems to humans—were divided into two groups and fed the capsules along with high-fiber and low-fiber diets. The capsules sent data every five minutes and went into sleep mode between transmissions to conserve battery power. Minimum life of a battery was four days, more than long enough for a capsule to complete its job and be excreted by the pig.

“The data showed that a low-fiber diet produced four times more hydrogen in the small intestine than a high-fiber diet,” said Kalantar-zadeh. “This surprised us greatly, given that hydrogen is made through fermentation; we expected more fiber would produce more of the fermented gas.”

In addition, high-fiber diets produced more methane gas in the large intestine than the low-fiber diet, suggesting that painful gas retention could be avoided by reducing the intake of high-fiber foods. They found that the ratio of carbon dioxide and methane gases in the large intestine wasn’t affected by the amount of fiber the pigs consumed, suggesting that neither diet would help people suffering IBS problems associated with methane concentrations.

The implications of these findings, Kalantar-zadeh believes, could lead to “trashing misconceptions everyone has about certain kinds of food being good for certain conditions.”

The group’s research started in 2009, when the first capsule was produced. The newest capsule, Version 5, which will be used on human volunteers, will employ a temperature sensor and two gas sensors. One gas sensor will detect oxygen and hydrogen; the other is a hydrogen sensor that is not sensitive to oxygen but can also detect methane and carbon dioxide.

In conveying the importance of the research, Kalantar-zadeh explains that microorganisms form a significant part of our gut and work with us in symbiotic fashion. When they digest food and when they interact with each other, they produce gases. If they are healthy, they produce gases with normal profiles. If they are under stress or if there is any disorder, then the gas profiles change.

“This provides us with very good health biomarkers that no one has looked at before because they were hidden from sight inside our bodies. But now we have an easy means to measure gas concentrations in the gut.” Consequently, he says, this method can be used to build libraries of healthy gas profiles, against which the gas profiles of individuals can be compared.

The researchers are working on modifications aimed at further increasing the value of the data measured by the capsules. For instance, more sensors need to be included in a capsule to provide multi-gas measurements. They’re also seeking a way to precisely track the location of a capsule as it travels through the gut.

It’s only a matter of time, Kalantar-zadeh believes, before the technology will help medical researchers “design personalized diets and drugs that can target problem areas in the gut and help millions of people around the world affected by digestive disorders and diseases.”


Tech Talk

IEEE Spectrum’s general technology blog, featuring news, analysis, and opinions about engineering, consumer electronics, and technology and society, from the editorial staff and freelance contributors.

Newsletter Sign Up

Sign up for the Tech Alert newsletter and receive ground-breaking technology and science news from IEEE Spectrum every Thursday.