What Gut Health Wearables Can and Can't Measure

A new wearable comes along every few months, promising to analyze something from your body that once required a lab. It started with sleep, then moved on to stress, and now it’s your gut. To be honest, the first time I saw a company claim that its device could measure my gut health with a patch on my belly, I thought it was nonsense. The problem isn’t that these wearables can’t detect anything useful. It’s that detecting digestive activity and measuring your microbiome are two very different things, and marketing often treats them as interchangeable. Let’s look at how these wearables work, since “gut health wearable” is doing a lot of heavy lifting in marketing copy right now. What These Wearables Actually Measure Here is the information that is never going to be in the headline. The device is unable to sequence your microbiome. No current wearable can tell you about the types of bacteria and their ratio that are residing in your colon. For now, understanding which bacteria are present in your gut and their relative abundance still requires biological samples, most commonly stool, analyzed using techniques such as metagenomic sequencing. The only information these devices can collect is downstream signals of digestion, some of which gut bacteria influence. Noise, gas and movement are produced due to the process of digestion. This is an entirely different aspect from the analysis of the microbiome and it needs to be understood well. The Patch Approach Probably the most buzzed-about product in this area at the moment is Suna. It’s an abdominal sensor patch founded by Dr Chad Okay, an NHS doctor and UCL researcher, and Selin Talishinska, an AI engineer, who built a way to listen rather than asking people to log their meals. The abdominal sensor patch captures the noise produced by the bowels through acoustic sensing, along with heart rate response, temperature and movement data and then feeds them into an algorithm that infers patterns such as a daily “Gut Readiness Score” and how particular meals line up with gut activity. To be clear about what is measured and what is inferred: the sensors measure sound, heart-rate response, temperature and motion. The score, the meal correlations and the bloating or constipation insights the company is marketed around are the algorithm’s interpretation of those signals, not direct measurements of anything inside your gut. There is no need for an app-based diary and scoring of your meals. The patch is listed with up to seven days of battery life, which is a real improvement over the previous approach of logging everything you eat. However, sound waves and movement are not the same thing as figuring out what you have inside your intestines. The device tracks digestive activity rather than microbial composition. Even the company’s own comparison of its device with stool tests and bathroom cameras highlights that they do not measure the same thing. It's Not the Same as a Microbiome Test One-time microbiome tests of the type where you send in a sample of your stool give you a static picture of real bacteria, as well as their distribution in terms of species at the time the test was performed. This approach looks at the microbes directly, but it is still only a snapshot: a single stool sample reflects only when and where it was collected, may not represent the gut lining, and can be affected by how it was collected and stored. There is also no single “healthy” microbiome profile to compare yourself against. There are no updates after that without repeating the test. In contrast, wearables provide a continuous record of data but indirect information. They measure the patterns in the way your body reacts to food and stress on a daily basis without taking into account the bacteria. Neither technology lies to the customer, as each answers a different question. But marketing can mislead people by using such phrases as “track your microbiome”, rather than “track digestive tract signals”. The Real Science Behind It Here's where I'll do my best to show where credit is deserved, since there actually is research supporting the broader idea of continuous gut monitoring, and it's not just the usual startup hand waving. There is an instrument known as Smart Underwear, developed at the University of Maryland, which isn't meant for consumer use but is intended as a tool for research that analyzes hydrogen gas emitted. I know it sounds a bit crazy when it's described like that. It's just that this is the first wearable to monitor the generation of microbial gases over time in the gut, and in one study it detected increased hydrogen production after participants consumed inulin, a dietary fiber that acts as food for gut microbes, with 94.7% sensitivity. That 94.7% figure comes from one specific experiment: a small study in which healthy adults ate inulin as a deliberate fiber challenge. It describes how often the device caught that known trigger. It is not a general accuracy rating for wearables, and it doesn’t cover everyday meals, other populations or other kinds of change. The researchers are now pairing the device with stool-based microbiome analysis in a larger study to see which microbes drive gas production. It's an actual, measurable signal from the bacteria, even though it doesn't tell us which particular bacteria generate the gas. It is evidence that continuous and passive monitoring of gut functions is feasible and scientifically sound, and it can stand up to scientific scrutiny, something that cannot be said about many of the wellness devices out there making health-related promises. The gut is not a small system in the body, which is one of the reasons that there is such interest in it to begin with. This is a valid reason for wearable manufacturers to take an interest in this area. The only problem is that the marketing is moving faster than the science. Where the Hype Creeps In That’s where I start to roll my eyes. Some of the nomenclature used for describing the function of gut wearables comes straight from the language of microbiology, such as dysbiosis, gut bacteria, and microbial diversity, yet no microbial testing is being done at all. And what’s more, you get the feeling that you’re getting the same information about your bacterial population as if you did some lab tests, when in reality you get a readiness score calculated from your sounds and movements using the model. Still, that’s not something worthless. It may reveal interesting patterns in bloating, transit time, or the effects of eating particular food on your next-day energy level. I’ve experienced it with other wearables, where the numbers themselves were not very useful but the data still revealed something that changed my behavior. But there's a distinction between "this device helped me realize that my eating schedule is throwing off my sleep patterns" and "this device monitored my microbiome." And only one of them is scientifically correct and it definitely isn't the latter. And then there's the issue of accuracy that is discussed not nearly enough. Abdominal acoustic sensing is a difficult process. The ambient noise, motion and clothing can all affect the sensor readings. Motion from breathing and abdominal muscle activity is a known challenge for bowel-sound sensing. These companies have not reached maturity yet, some of them are even in pre-production stages and the research that has been conducted is often limited to small sample sizes (the Smart Underwear study above is one example). This is not to say that it's necessarily a problem, as all wearables have to start somewhere, but it does mean that you're early to the science as well. So Can a Wearable Track Your Microbiome? No, it does not. But what it does offer is the ability to track signs affected by your microbiome and provide you with ongoing data on digestive patterns, which until now mostly meant keeping a diary and making a lot of assumptions. It is very useful. Whether it is worth calling it microbiome tracking depends solely on the marketing department. It is not what you should expect from such a device if you hope it will be a wearable equivalent of stool sample testing. However, if you are looking for a way of passively noticing patterns related to bloating, energy level, and how your body reacts to certain foods, it might prove quite helpful for the moment. I am likely to try one of these devices myself once they become more widely available, not because I hope to know what kind of bacteria live inside my gut, but because I would like to see what kind of patterns will emerge when I do not have to actively record them. This is where the value of wearable technology lies, actually.