Our microbiome, the vast ecosystem of yeast, fungi and bacteria that inhabit the gut, has one overriding function: to keep our bodies ticking over in good health. With an estimated 4,600 species of bacteria, the precise combination of our intestinal flora is as unique to us as our fingerprint but it influences everything from sleep and stress levels to immune strength and ageing. And the more research has highlighted the importance of this gut garden, the more of us have used products aimed at helping the microbiome to flourish.
The global gut health market, which includes probiotic, prebiotic and postbiotic drinks, foods and supplements, is predicted to reach £79 billion by 2029 — an increase from £53 billion last year — and demand has risen for DIY gut health testing kits, which promise to tell you what microbes you are carrying and what might be missing from your personal gut portfolio. These tests cost anything from £119 for a basic product to £399 for comprehensive feedback. Are they worth it?
Not according to researchers from the University of Maryland and the US National Institute of Standards and Technology (NIST). Often, says Diane Hoffmann, director of law and health care at Maryland, the results they give are inconsistent with large discrepancies in information provided about gut status. When she and her colleagues dispatched three identical stool samples to a range of commercial laboratories, they yielded very different results.
Findings published in Communications Biology journal revealed that some commercial labs identified the same types of bacteria but in widely varying amounts, while others sent back drastically different bacteria levels from identical samples.
“The hype about these products doesn’t match the evidence,” Hoffman says. “The marketing can be questionable and consumers can end up misinterpreting or over-trusting results that aren’t very reliable.”
Stephanie Servetas, a NIST microbiologist who also worked on the new study, says analysing the microbiome is a challenge. “It isn’t like measuring blood glucose, for example, it’s measuring a collection of things,” she says. “And we don’t know how well what is measured actually represents what is in the gut microbiome, given that it is a many-step process to go from stool sample to report, and each step can introduce variability.”
For those in pursuit of gold standard gut health, the researchers stress there is no such thing. “There is some agreement that diversity is a good thing,” Hoffman says, “but we don’t know which specific micro-organisms are necessary for a healthy gut.” If your gut is churning as you digest this news, here’s what you need to know to keep it healthy.
How do gut microbiome tests work?
When you do a gut health test you will need to send a sample in a container to a lab for analysis. “Many commercial companies now use DNA sequencing tools to estimate how many types of bacteria are present in your stool sample,” says Julie Thompson, a gastroenterology specialist dietician and spokeswoman for the charity Guts UK.
You will be sent an analysis referred to as your microbiome profile or fingerprint, often in the form of a numerical score, which is often accompanied by recommendations to manage the levels of some bacteria in your gut through diet or probiotic supplements. Advanced tests will sometimes measure other markers of gut health, such as levels of calprotectin, an indicator of inflammation.
What they won’t tell you…
While gut health knowledge is gaining pace, there is much that is yet to be discovered about the human microbiome. At best, Hoffman says, a test “might be able to tell you some of the micro-organisms you have in your gut but they can’t tell you what that means”.
One problem is that the science behind faecal DNA analysis isn’t yet advanced enough to produce reliable conclusions and we are still a long way from knowing about all of the micro-organisms that live in our gut. Research from the University of Cambridge recently revealed that about two thirds of bacterial species in the gut are part of a “hidden microbiome” that have not yet been grown or analysed in a lab. These and other unidentified but potentially important gut bugs would not show up in DIY tests.
“Many gut bacteria get stuck to the gut wall so might not show up in faecal samples and DNA tests won’t tell you if a bacteria is dead or alive — just that it was present at the time of the test,” Thompson says.
Are there any tests worth paying for?
Despite the lack of accuracy, gut health tests are not necessarily meaningless. Dr Linia Patel, a spokeswoman for the British Dietetic Association, says that many of the big players, such as Viome, Ombre and Zoe, look for diversity of microbes.
“I don’t think the tests are necessary as you can achieve desired gut changes without them,” she says, “but those that encourage microbial diversity through a healthy diet are probably the ones to opt for if you do want to try one.”
Servetas recommends looking for tests that offer detailed descriptions of the testing process and reports that include references to good research on their website. “I would be wary of any company that is trying to sell you on a product after taking the test,” she says.
If you do want to take a test, when is the best time to do it?
Conor Meehan, associate professor of microbial bioinformatics at Nottingham Trent University, says now is as good a time as any. “It’s best to pick a time when you are as healthy as you are likely to be and in a regular routine,” Meehan says. “Spring is a good time of year because we are over the winter viruses and have yet to go on holiday, which is when we often eat and drink differently, and are likely getting outside a bit more.”
Will you need to redo the tests every few months?
When you do a one-off gut test, it provides an insight into your bacteria on that day. Taken at another time, a sample from the same person can be different. “A bowel movement isn’t even consistent across the length of the stool, or from inside to outside,” Servetas says. “Given that many of these companies process only a small sample, the best you are getting is a snapshot.”
There’s an argument that these tests only become useful when they are conducted regularly and at different times. “At the moment there’s not much use in repeating tests as they are not accurate enough,” Meehan says. “But things are evolving and in five years, when the tests might be more accurate, it could be worth sending a couple of different samples through the year.”
Does the data predict your risk of some diseases?
A single sample won’t tell you if you have protection against heart disease or are at risk of getting type 2 diabetes. “Any test that claims to diagnose actual disease hasn’t really substantiated that, or if they have, they haven’t published those results [in peer-reviewed journals],” Hoffman says.
Some tests do check for pathogens that might cause infections. “We know that certain microbiome signatures will come with disease,” Meehan says. “So we know that if you have a C. difficile infection it’s going to be mostly C. difficile in your stool sample because it takes over the microbiome.”
If you received results from a gut test that listed a pathogen and were experiencing gastrointestinal symptoms, it could be worth discussing with your doctor and potentially seeking a confirmatory test. In the future microbiome testing is likely to be a big player in precision nutrition and disease prevention. “Regular testing could eventually be useful in unpicking longer-term microbiome trends that come with the menopause and ageing,” Meehan says. “But we are not yet at that stage.”
Will the results help you to improve your gut health?
This is the big selling point with many companies advising changes to diet and lifestyle based on the results of a test. Thompson says that if you use the results to improve your eating habits, and in turn enhance your gut health, then that’s a positive.
“In most cases it is not the gut health test that has helped, it is the actions people take as a result of them,” she says. “Because they feel better it’s a confirmation that what they have done has worked, but the tests are little more than a turning point for change and you can adopt healthier eating habits for free.”
However, it can also backfire. “I have clients who are extremely stressed after taking these tests and being told they have poor microbiome status,” Patel says. “And stress is not good for gut health.”
Should you take a probiotic if you are concerned about your gut health?
Probiotic supplements provide a dose of beneficial bacteria. They are a go-to for anyone concerned about gut health and are often recommended after microbiome analysis. But choosing which to take is not as straightforward as picking any product off a supermarket shelf.
“What works for one person won’t necessarily help another, and that is down to your personal microbiome profile being different,” Thompson says.
Probiotics delivered in food are naturally protected against stomach acid so don’t overlook natural live yoghurt or kefir and fermented cheeses such as stilton, aged cheddar, parmesan and gruyère as gut-friendly options. “Save your money and add these along with diverse plant foods to your diet for a healthy gut,” Patel says.
How do you tell if your gut microbiome is healthy without taking a test?
Getting your five a day and 30g daily of fibre — the latest government National Diet and Nutrition Survey in 2025 showed adults have an average intake of only 16g — will help to keep your gut in tip-top condition. “Being aware of your digestive health is important — do you bloat excessively or have acid reflux to a point it is impacting your quality of life?” Patel says. “And any changes in bathroom frequency or consistency of your poo could mean changes to your gut health, and you should see your GP if it continues.”
gutscharity.org.uk
