Is Your Gut Test Actually Accurate? The Problem Most Companies Hide | Dr. Tim Spector

Added: 2026-05-07

[00:00:00]What do you want to look for as a consumer to know that the the gut test that you're ordering is actually the latest technology that that can detect the good and bad bad species that we're talking about? It should be what's called shotgun metagenomics, which means you look at every gene in every microbe and you put it together like a giant jigsaw puzzle, which means that you shouldn't be taking something like 16S or PCR, which are the old-fashioned genetic methods. And you want to be able to Nobody else has done this yet. It takes quite a lot of time before a company can rejig its itself to do this, but in the future, you'd say, "Okay, we're going to use this ranking system the you know, these good and bad bugs and we can show you something about how they're doing."

[00:00:49]They might still present the diversity score to give you a a sort of sense check of where you are. That would be perfectly normal, but you have to appreciate that most of the good bugs don't have names or and they just have numbers. So, the current companies out there, particularly in the US, which were tested recently by some academics who ranked seven companies, not including Zoe, but they were tested and found they weren't very reproducible either. So, that means that if you send the same sample twice to the company, you got a different result.

[00:01:22]And those results are really quite disappointing and it means that a lot of these companies aren't set up for really accurate results because there are lots of technical difficulties in doing a gut sample that is means you have to be extremely diligent and consistent that only the very best labs do. And if you don't do that, you get big differences between the same sample.

[00:01:50]You wouldn't see any good scientific results, for example. And so, you should always ask, "Do you have any reproducibility data?" I think that would be a another way of doing it. Or have you published any good papers using this data in you know, high-ranking journals? Cuz if you got poor reproducibility, you won't find simple correlations. Is Zoe using the shotgun metagenomics and the this new rating system or is the rating system something that you'll roll out in future? No, I mean, since the start, we've used shotgun metagenomics. That's that's the state of the state of the art at the moment. The only thing that changes in that is using the latest software that includes the database to include the genes so you can link up the genes that you're finding with the microbes that are being identified. So, you you sort of match them together. And that's that's the thing that has to be permanently updated and often it's only the the latest academics that have the very latest software and things to do this. That's why we took the the course of working with academics on this project because commercial ones do struggle to to have the very latest data and information. So, it it's not as simple as just taking your gut test report and uploading it into Claude or some other AI along with your nature paper and it's going to give you your rating. I haven't tried it, but I'd be very surprised if it does, but do give it a go, Simon, and you never know.

[00:03:21]AI is getting better all the time. It may be soon be a possible to do that, but you need the report and the list of the you know, your your top what's really interesting is that just in the four years since we published our last paper, the top 50 microbes, you know, most of the old ones that that made the top 10 last time didn't make our list of top 50. So, there's a sort of dark matter of of good microbes that have have been there that we haven't even picked up yet. Most of the bad ones we know about, we've heard about, but the good ones we really didn't realize they were good. And that's the other sort of key thing that came out of this paper that really surprised me. It's we've been looking at the wrong guys and that we need to work out who these guys are, you know, and what they eat and how to really encourage them. Does that change the way that you think about probiotic supplements at all and and kind of traditional probiotics versus potentially what that category might look like going forward or are you still mostly of the view that you need to feed your own gut bugs rather than taking a supplement? We're looking at both approaches and I think they could be complementary. Obviously, we could take our top 50 bugs and give it to some amazing company who could culture them and produce a a giant capsule and then give [snorts] that to humans and that might be commercially available in you know, 10 years' time probably because it's a lot of work, but we don't know whether they would work as a capsule, whether they would you know, you could get them to grow back in your body or not.

[00:04:57]All these things are unknowns. So, it's a lot riskier doing that than the approach that we we currently we have, which is focusing on the fertilizers, the prebiotics. And a lot of this thinking came from we developed our prebiotic called Daily 30, which is over 30 plants, a lot of them freeze-dried in their whole form without really worrying about it, just saying a big diversity of plants that you don't normally get in your gut, lots of fungi, lots of herbs, spices and and other things that give you fiber. We tested that against a probiotic in a randomized trial and a placebo using this new scoring system and we showed that we can increase I think it was I can't remember the exact numbers, but I think it was over 30 of the good bugs increased in frequency out of that fit top 50 in the group taking the prebiotic, whereas only about four increased with the probiotic. And this was it was a single strain probiotic, but Lactobacillus reuteri, which is a really well-known proven probiotic.

[00:06:04]So, it just suggested that it's a much safer bet at the moment given we've all got very different gut microbes to think of a prebiotic approach rather than gambling on one species or even a group of species to to do the same job. So, that's our current thinking, but we are still trying to develop some probiotics and test them, but get it from humans, cultivate it, grow it up in mice and bugs and get it into a capsule. It's years of work. It's a a very slow process, whereas fibers are fibers are easier. Is the personalization piece there yet in term in terms of someone provides a stool sample, they get a microbiome rating? Do we understand at a kind of individual prescription level what specific foods will lead to the growth of specific good gut bugs that maybe someone doesn't have a a lot of and therefore a very individualized approach to the way that they should eat above and beyond say general messaging, which you speak about a lot where it's like plant diversity, high fiber, fermented foods, try and limit ultra-processed foods. When you actually do this testing, does it give you that granularity yet or is that is that where we're hoping to get to in the future?

[00:07:24]It gives you a little bit, but I think [clears throat] we're only a a small way on this journey. We're only really touching the edges of it. And we've got a nice analysis in one of our papers I think where we we look at 30,000 people and we have gut health on one axis and the key sort of factors that influence it on the other. The one that always comes up top is plant diversity overall.

[00:07:50]And then we looked at the individual foods that do that. The number one that came up was coffee, right? So, I could tell you very precisely how to increase one microbe, which is called Lawsonia bacteria.

[00:08:03]You can get it increased sixfold by having a cup of coffee. So, we know it's possible, but we're slowly dissecting the other ones that are lower down the list. And to do that, we need these big big samples and it takes a lot of computational time to do that. So, we're now at the point where we can statistically say, you know, these are your good bugs, these are your bad bugs, these are the foods that are associated with those. You should eat more of these ones for your gut health.

[00:08:37]At the moment, it's fairly crude and it's statistically true, but may not be really impactful from an amount point of view, but every year we're getting better at doing this. So, our advice is continually improving and I think that's that's the hope that as our numbers increase and we get towards a million people and we get more longitudinal data as well, so we're starting some studies where we're giving people certain foods and looking at how they respond, we can start really to to drill down more and give more precise specific food indications rather than general food indications. Also, with the the addition of being able to pull results from labs all around the world now if they're using that that rating system with interventions. Yes, exactly. So, we needed to work out a good scoring system so we can actually test, you know, how well these foods work. And now we've got we can really see in you know, very clearly in our studies now, can you move these 50 bugs? Not only, you know, it gives you a much more precise way of looking at them. So, you can see how they're changing and this is what people get when they repeat their their Zoe tests now. You can see how your your gut microbes are changing. I think that it's very motivational as well because it it helps you get towards these goals and we have grouped them into clusters whereby, you know of these hundred there are certain ones that are related to the immune immune cells from their genes and others related to metabolism and things like this. So as we go on we will be able to ascribe better functions to these things as well. If you've been listening to me or some of my guests talk about the gut microbiome, you'll know that it thrives on very specific types of fiber and polyphenols and resistant starch. Many of which the average person falls short on despite the very best of intentions. That's why Dr. Will Bulsiewicz and I founded 38T era, a gut health company where science meets supplementation. An independently conducted 15-day M-Shine study found that our first product, daily microbiome nutrition or DMN for short, significantly increased short-chain fatty acid production and encouraged the growth of beneficial microbes linked to better gut and metabolic health. It's a simple daily scoop that you can add to water or your smoothie. No sugar, no fillers, just clinically backed ingredients that make your gut bugs happy. So if you want to support your microbiome in a meaningful, science-backed way, check out 38t.com and [snorts] use the code the proof to save 20% off your first order.