Biome Bite 014 - Debunking 3 Microbiome Myths

In this Biome Bite, Dr James McIlroy 3 myths and misconceptions about the gut microbiome.

Timecodes:

00:00:00 Intro

00:00:56 Weight of the microbiome

00:04:39 We’re more microbial than human

00:07:00 Microbiota is inherited from our mothers

 What we're talking about today on this Biome Bite is microbiome myths and misconceptions. We're going to cover 3.

There's this lovely article written by Professor Alan Walker, who's been on the podcast, highly recommend you watch and listen to that episode, and Professor Leslie Hoyles and it's in Nature Microbiology, so really nice high-impact scientific journal, and they go through a lot of the things which you hear within this space, be it in social media, be it in when you're speaking to someone who's just generally taking an interest in the microbiome, even in scientific papers, this still comes up, even though it's been refuted and proven to be untrue.

Arming Our Listeners With Facts About the Microbiome

So we're going to arm you as the listeners to Inside Matters with this knowledge so that you can truly start to become an expert and you've got your finger on the pulse of the field. And if you hear it, you go, I heard on inside matters. That's not true.  So the first one is the human microbiota weighs one to two kg.

You hear this a lot, several kilograms, almost like a weight plate at the gym. Wow, that's a lot.  Now although it's mentioned many times in literature, although you hear people talking about it, people say it weighs as much as a grapefruit.  And what the professors do in their papers, they explain that. The majority of the microorganisms reside within the colon,  i. e. the large intestine. And if you've listened to the previous Biome Bites episode, we walk through the digestive tract, the gut, what the gut is, what the digestive system is, how it all links together and how the microbiota fits into all of that. 

And in that episode, if you've not listened to it, what we say is that the vast majority of the microbiota, i.e. the microorganisms, particularly bacteria that reside within the body live in the large intestine.  And what's interesting is when you take a stool sample, or we can just use the other word, a poo the microorganisms typically account for roughly 50% of the weight of the faecal solid mass. 

This has been published, but also we've done a lot of stool collection and stool analysis in EnteroBiotix. In fact, we may collect more stool regularly and analyze stool in a more in-depth manner than anyone else in the world at the moment.  So we know a fair bit about it.

How Heavy is the Microbiome?

The size, shape, mass, and composition of stool can vary within an individual and also differ among various people. According to the paper, an average human stool typically weighs less than 200 grams when wet. However, in our experience, we have observed significant variations, which makes it a likely accurate statement.
And when you're running a donor program like EnteroBiotix, you actually want to target people who donate larger amounts, but also who have a good ratio of microorganisms versus solids. And that's driven by fibre and fibre content.  Now, they say a really interesting paper in patients or people, unfortunately, who have had a sudden death.

The human microbiota, particularly the gut microbiota, plays a crucial role in maintaining our health. The weight of these microorganisms has been the subject of many studies, and recent findings suggest that the total weight is likely to be less than previously thought. In sudden death cases, post-mortem assessments of the total colonic contents have shown a range between 83 to 421 grams. This data challenges earlier estimates that placed the weight of the human microbiota in the range of one to two kilograms.

Researchers concluded that barring unusual instances of severe constipation, where an individual's colon is compacted with a large amount of faecal matter, the total weight of the gut microbiota is more likely to be under 500 grams. This new understanding shifts the narrative about the microbiota's mass and provides a more accurate picture of human physiology. It also emphasizes the importance of considering bodily variations and conditions when making generalizations about biological metrics.

These findings have significant implications for medical science and nutrition. A more precise understanding of the microbiota's weight can impact how we approach digestive health, the development of probiotics, and the treatment of gastrointestinal diseases. It underscores the importance of continual research and reassessment in the scientific field to ensure our knowledge remains as accurate and useful as possible.

The human microbiota, particularly the gut microbiota, plays a crucial role in maintaining our health. The weight of these microorganisms has been the subject of many studies, and recent findings suggest that the total weight is likely to be less than previously thought. In sudden death cases, post-mortem assessments of the total colonic contents have shown a range between 83 to 421 grams. This data challenges earlier estimates that placed the weight of the human microbiota in the range of one to two kilograms.

Researchers concluded that barring unusual instances of severe constipation, where an individual's colon is compacted with a large amount of faecal matter, the total weight of the gut microbiota is more likely to be under 500 grams. This new understanding shifts the narrative about the microbiota's mass and provides a more accurate picture of human physiology. It also emphasizes the importance of considering bodily variations and conditions when making generalizations about biological metrics.

These findings have significant implications for medical science and nutrition. A more precise understanding of the microbiota's weight can impact how we approach digestive health, the development of probiotics, and the treatment of gastrointestinal diseases. It underscores the importance of continual research and reassessment in the scientific field to ensure our knowledge remains as accurate and useful as possible.

And that's based on the average weight of human stool. And the study shows that the average wasn't backed up by lots of wet research and scientific logs and books, it's just the back of an envelope.  And since then there's been a lot more detailed analysis. and the true figure is probably more like one-to-one. Now that's still really impressive. That is a lot of microorganisms.  And the interesting thing is, just to bring it back to the last point about the number of microorganisms in a stool sample,  whether you're more microbial than human or more human than microbial based on the number of microbial cells on the inside of you versus human cells depends on perhaps when you've been to the toilet. 

Because if 50% of your stool which is a sum product of the colonic contents is a microorganism then if you've just been to the loo you may be more human than microbial and vice versa. So a bit of trivia there for you.  The other point to note which is highlighted in the paper is that it probably varies as well depending on where in the world you are.

So if you're in a hyper-clean environment, you have less than someone who's living in an environment where there's no soap and no antibiotics like somebody in the jungle somewhere. So pretty interesting stuff.  Now, the last one then,  is that the microbiota is inherited from the mother at birth.  And you hear this one a lot and it usually ties into how someone's been born.

So people say things like if you've been born by C-section, you're more likely to have autism or you're more likely to have metabolic syndrome. You're more likely to be obese, all of which are potentially true based on population-based studies, i.e. they take large cohorts of people who have something, in some cases autism, metabolic syndrome, or obesity, and they ask the question, how were you born?

And if more people cluster towards a particular birth method than when you take a healthy control group,  then it's possible that this particular factor contributes to the development of the disease or the syndrome or whatever we're talking about here. 

The more this is replicated in different parts, the larger the sample size, and the more robust it is. And there have been very large population studies where we've looked at the association between how you've been born and the development of obesity, autism, and certain things like that. And there are indeed correlations, for sure. But it doesn't necessarily mean causation,  it's still interesting though. Bringing it back to this particular point in terms of the microbiota being inherited from the mother.  The other point to this is that if you're being born through the normal route, then the first microorganisms that you come into contact with, the normal being through the vagina are the microorganisms of your mother and the vaginal tract in a natural way. 

The alternative approach is if you're born through a C-section, then the first microorganisms you come into contact with.  are the microorganisms from the skin and microorganisms from the surgical room. Some of these are multi-drug resistant and they're not ones you would typically expect to find within the intestinal tract. 

How Unique is Your Microbiome?

That said, it's not the case that they stay there forever, guaranteed. And the most important years of life are the early years of life, particularly when you've weaned off breast milk or however you've been fed at the time to more solid foods.  And there's a dramatic increase in the diversity of the microbiota over the first couple of years.

And I could point you in the direction of a nice book called Dark Matter by someone called Dr James Kinross, whom I hope to have on the podcast, where he talks about just how important those formative years are that said, every adult ends up with a very unique microbiota composition.

It's as unique as a fingerprint. How do we know that? We can assess the microbiome in identical twins who have the same genotype,  who've been in the same house, sometimes most of their life, or certainly up until the point of testing, and they have distinct microbiota. So it's the sum of everything you've eaten and everything you've done up until the point of testing. 

And there can be dramatic changes, but as you get older, it starts to get a bit more stable.  So although Microbiota assembly from birth is not yet fully understood. We do think that the adult communities are predominantly shaped by the early years of lives and factors such as diet, antibiotic therapy, and host genetics, rather than just being purely inherited from the mother. 

So there are three microbiome myths and misconceptions debunked. I hope you've enjoyed it. Thank you so much for supporting the podcast, and for taking an interest in your gut health and your microbiome. I'm open to feedback and we do the five-star reviews. Please keep them coming because it lifts and elevates the podcast across all the channels.