Like others around the world working on human genome research, scientist Mark Driscoll believed that cracking the DNA code would ultimately deliver the cure to cancer. There were many high points during his years leading next generation sequencing (NGS), the tech that allows us to read and analyse our genes. His team sequenced James Watson’s DNA, for example, and Nobel Prize winner Svante Pääbo used it to decode the Neanderthal genome.
But, as we know, it didn’t solve the riddle of cancer. However, Driscoll hasn’t given up on this goal. And now he’s convinced that the key to curing cancer is hiding somewhere else: our poo.
“When we didn’t figure out cancer, it was a disappointment,” Driscoll admits. “In the decade since, people have been pointing out, ‘When there’s colon cancer, we always see these bacteria. When there’s pancreatic cancer, we always see these bacteria. When we see breast cancer, we always see these bacteria’.” The frequency of these observations propelled him to redirect his efforts to looking at the gut microbiome, flush with around two million bacteria, each one with its very own set of 3-5,000 genes.
Driscoll has set up his own company, Intus Biosciences, based in Connecticut. He wants to not only improve cancer diagnosis and treatment, but also that of IBS, as rates of bowel cancer soar internationally, in particular among the under-fifties living in Western countries. In the UK, early-onset bowel cancer cases have increased by 25 per cent in the past decade.
To get closer to the solution, he has created a unique test called GutID that identifies every strain of bacteria in our gut microbiome, giving scientists – and punters lucky enough to try the test – a complete picture of our guts. This picture is represented by a glorious, multicoloured pie chart, with labels that, to my untrained ear, sound operatic: Segatella, Sutterella, Prevotella, Roseburia. They are bookended by a ring of bacterial strains tagged by number as they’ve never before been documented.
“Human DNA has not changed in the last few generations,” explains Intus Bio’s chief executive Paul Denslow, a Brit with a background in banking and biotech. “All that time and effort and resources have gone into looking at the 23,000 human genes. We need to look at the two million bacterial genes in the body, which we know have changed in the past couple of decades because of diet, food production methods and antibiotic use, as cancer rates have changed dramatically.”
With a few thousand test samples so far and collaborations with Imperial College London and Oxford University in the UK, Denslow is keen to take Driscoll’s test to a much wider audience.
Should healthy people, or those with no family history of cancer, test? “Gut bacteria is a fundamental driver of health outcomes,” says Denslow. “The point is to look at bacteria to help people manage it so they can avoid or delay disease development. It is something you can track and positively influence.”
Though I don’t have any worrying gut symptoms or a family history of cancer, I am of the generation falling foul of rising cancer rates. As a middle-aged woman I’m brainwashed by advice to consume kefir and kombucha but I do eat everything, including ultra-processed foods, and might trade a family member to keep marbled steak and fatty salami on my dinner table.
I wouldn’t have shelled out for the £349 test if I wasn’t reporting on it. But I am delighted at the opportunity to see inside my mysterious microbiome.
I am, though, sobered by the opinion of King’s College London microbiome scientist Emily Leeming, author of Genius Gut (Penguin, £18.99), who suggests it could be a waste of time.
“Microbiome testing isn’t advanced enough yet to get any actual advice that we can’t get elsewhere for free,” she warns me. “These tests are incredibly expensive, and they’re often selling promises that we do not have enough credible evidence to support. If you are looking to improve your gut health, see your GP or maybe pay to see a dietician.”
The test is easy enough to do. I take a tiny sample with a plastic scoop, pop it in the envelope provided and wait for my results.
A month later, I received a 20-page report of my “Core Gut Insights”, headed with an overall score out of 100 and a few key points. The good news is that I’ve scored 74, a result described as “good” by the report and “very good” by Elena Panzeri, the specialist microbiome nutritionist who will help me to interpret the results.
(In a second test six months on, my score was recalibrated down to 68, by which time the GutID database had grown and they could standardise my initial score against more data).
But the news is broadly positive. I have no fusobacteria, which Driscoll says is present in all the disparate research on gut bacteria and cancer, and only in people with cancer or very ill from food poisoning. “People ask if it’s causation or correlation,” he says. “We know those bacteria are there before there’s cancer. Recent work has shown that these bacteria can actually cause the DNA breaks that are causing cancer.”
I also have a good level of diversity and plenty of the bacteroidetes and firmicutes (shown in purple and tan on my pretty poo wheel) that should make up the majority of a healthy microbiome. But there are a few interlopers, including a pathogen called mycoplasma, which I’m told is pretty rare and not welcome in my gut, as well as a low level of probiotics.
In preparation for a follow-up test I discuss ways to work on my gut bacteria with Panzeri.
I started taking two probiotics, Thorne bacillus coagulans and Optibac Every Day. I also started eating more fibre and polyphenol-rich foods, such as green tea, kefir, berries, dark chocolate, Evoo and almonds. I am gunning for a perfect score, something Driscoll almost achieved, remarkably, after 14 weeks improving his diet of “black coffee all morning, peanuts all afternoon, and whatever’s for dinner.” He started off with a score of 28, which remained stable for 14 months. After eating Panzeri’s menu it shot up to 92.
Colorectal surgeon James Kinross, who researches bowel cancer and the gut microbiome at Imperial College London, uses the test in his clinical practice.
“These are not diagnostic tests,” he explains. “We use them in a way that gives us functional insight into what’s happening in the gut of the patients I look after.” Was he using another test before this one became available? “I wasn’t,” he tells me. “The direct-to-consumer microbiome tests aren’t fit for purpose. A lot of them previously used short read 16s sequencing, which means that you don’t get down to species or strain level.”
Zoe is the best known gut health test in the UK and the company that popularised mainlining fermented foods and studying one’s own poo. Co-founder Professor Tim Spector, recently wrote a piece criticising 16s testing compared to Zoe’s metagenomic approach, which uses a tool called MetaPhlAn to give a view of over 5 million genes. Previously Zoe identified 15 “good” and 15 “bad” bacteria for users, but in 2024 expanded its list to 50 of each.
But other independent experts question how we classify and explain bacteria to a general audience – i.e. non-scientists like me. “There’s no such thing as good or bad bacteria,” says professor of vaccine immunology John S. Tregoning, also at Imperial. Tregoning experimented with gut microbiome tests for his recent book Live Forever? A Curious Scientist’s Guide to Wellness, Ageing and Death (One World, £18.99).
He took a 16s test, via work rather than bought from one of the many available brands. Should we spend £200-plus on these tests? “Don’t do it!” Tregoning says. “Join a tennis club, a choir, or a dance class. The whole thesis of my book is to spend your money on doing something nice with your friends, on something you enjoy that has a physical element.”
What about the improved science of tests like GutID? “The actual testing element sounds really good,” he continues. “What they’re doing is as good as you can do it. But the inference of the data afterwards is tricky. If you’re curious, why not have a look, but it’s scratching a curiosity rather than anything else.”
“I’m not saying what they’re doing is wrong, just that it’s so complicated at the moment, it’s hard to know what’s what.”
Like me, in the 16s test he took Tregoning was low in probiotics when he tested, but a diet of Yakult did nothing to improve his levels.
I took my second test after two months of probiotics and polyphenols, though after Christmas when I also majored on mince pies doused in brandy cream. I’m delighted to learn that my score has gone up, to 76, and the unpleasant mycoplasma, a “relatively rare pathogen”, has shrunk to what Driscoll calls “a reasonable slice”. Better still, it’s been replaced by more promising bacteria. As with Tregoning, there was little change in my probiotics. Something called proteobacteria, associated with IBS, has gone up slightly.
What everyone I speak to agrees on is that there is plenty to be learnt about our health from the gut microbiome, and it is the source of future medical breakthroughs. James Kinross has great hopes for the near future. “You’re going to see validated biomarkers in the next five years for bowel cancer screening and protection, also for reducing risk. I hope this translates into much better outcomes.”
Will I test again? After my second test, I needed a five-day course of antibiotics for a toothache, the first in a decade – treatment described by Driscoll as “setting fire” to my gut bacteria. Of course, I’m intrigued, and agree to test the hypothesis with another sample which I send off two weeks after taking the antibiotics.
I await the results with interest. I’m not paying for the experiment, but I can see how easily carrying out these kinds of health investigations could become addictive – and therefore, though fascinating, not suitable for someone on a writer’s budget, like me.
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