WEBVTT
00:00:03.200 --> 00:00:11.519
Approximately ninety-five percent of the body's serotonin is produced in the gut, not the brain, the gut.
00:00:12.720 --> 00:00:24.239
That single fact, which is well established, not contested, and has been known for decades, changes something about how we think about mental health.
00:00:25.280 --> 00:00:41.039
If serotonin is central to mood regulation and most serotonin is produced in the gut, then the gut is not just a digestive organ, it is a participant in your mental health.
00:00:42.320 --> 00:00:52.640
The question is what that means and the answer is more complicated, more interesting, and more uncertain than most of what you'll hear about it.
00:00:52.960 --> 00:00:55.840
Today we are going to go there.
00:01:20.719 --> 00:01:41.120
A podcast about mental health founded in science and I am Torin, not a therapist, not a clinician, someone who has spent 20 years inside these questions.
00:01:42.000 --> 00:01:45.439
And this is what happens when I ask them out loud.
00:01:46.480 --> 00:01:55.519
This episode is episode eight, and I want to prepare from the outset about what a kind of episode this is.
00:02:08.639 --> 00:02:24.719
The science here is real, substantial, and genuinely changing how we understand the relationship between the body and the mind.
00:02:28.479 --> 00:02:46.240
It is also one of the most heavily marketed areas in the biology industry, probics, psychobotics, methods, what the particles, the commercial ecosystem, and only science, is it enormous and learning.
00:02:49.039 --> 00:03:04.080
This episode is going to give you the after science, what the research is, I think it doesn't understand where the line sits between what we genuinely know and what is being shown on the basis of what we know.
00:03:15.599 --> 00:03:23.520
I want to start with something that many people who have lived with depression for a long time will recognise.
00:03:24.080 --> 00:03:26.400
The physical dimension of it.
00:03:26.639 --> 00:03:45.759
Not just the heaviness in the mind, the heaviness in the body, the stomach that doesn't feel right, the appetite that disappears or becomes relentless, the gut that seems to respond to emotional states before the brain has fully registered them.
00:03:47.120 --> 00:03:57.120
If you have noticed that your gut and your mood seem to move together, that anxiety lives somewhere in your stomach.
00:03:57.840 --> 00:04:07.199
That depression dulls your appetite, that certain foods change how you feel in ways that seem to go beyond digestion.
00:04:07.759 --> 00:04:10.080
You are noticing something real.
00:04:12.240 --> 00:04:20.079
The relationship between the gut and the brain is not a metaphor, it is a biological reality.
00:04:21.279 --> 00:04:28.720
And the research into it is one of the most exciting developments in mental health science in recent years.
00:04:29.920 --> 00:04:36.560
The question is what we can actually do with it, and that is where things get complicated.
00:04:40.240 --> 00:04:42.959
The usual frame before we go in.
00:04:44.079 --> 00:04:48.959
I am not a gastroenterologist or a microbiologist.
00:04:49.120 --> 00:04:57.120
Everything that I share today comes from published peer reviewed research sources are in the show notes.
00:04:58.720 --> 00:05:03.439
I want to hold the same standard I've held across the series.
00:05:03.839 --> 00:05:06.639
What is then established I'll say so.
00:05:07.600 --> 00:05:16.480
What is emerging and promising or name it as that, what is contested or clear, I'll say that too.
00:05:17.360 --> 00:05:29.439
This episode covers four things first what the gut of brain access actually is and how the communication between them works.
00:05:32.079 --> 00:05:40.160
Second, the serotonin question what the gut has to do with it and what that means for mental health.
00:05:41.199 --> 00:05:50.800
Third, what the research on probiotics and the gut microbiome actually shows for depression and anxiety.
00:05:51.199 --> 00:05:59.360
Fourth, what we can reasonably take from all of this and where the honest limits of that are.
00:12:28.799 --> 00:12:32.720
Which leads us to the microbiome itself.
00:12:37.759 --> 00:12:51.919
The gut microbiome is the community of trillions of microorganisms living in the digestive tract, bacteria, viruses, fungi, archaea, approximately 1,000 different species.
00:12:52.480 --> 00:13:01.120
Each person's microbiome is unique, shaped by genetics, birth, diet, medication, stress and environment.
00:13:02.799 --> 00:13:11.519
And the research connecting microbiome health to mental health is one of the most rapidly developing areas in all of medicine.
00:13:13.200 --> 00:13:18.240
Frontiers in Microbiology 2025 Systematic Review.
00:13:18.480 --> 00:13:33.600
Studies involving animal and human subjects suggest an association between gut microbial diversity and mental health, indicating that microbiota disturbances may contribute to depression onset.
00:13:37.919 --> 00:13:56.960
People with depression often show lower levels of SCFA producing bacteria, higher levels of pro-inflammatory bacteria, increased intestinal permeability, altered tryptophan metabolism.
00:13:57.440 --> 00:14:09.759
Early life stress causes significant changes in gut microbiome composition, and these changes appear to mediate some of the neuropsychiatric effects of that stress.
00:14:11.440 --> 00:14:16.799
That Mendelian randomization finding is particularly significant.
00:14:17.919 --> 00:14:21.360
Causative, not merely correlational.
00:14:22.480 --> 00:14:30.080
The microbiome dysbiosis appears to be contributing to depression, not just occurring alongside it.
00:14:35.440 --> 00:14:39.120
That is an important step forward in the science.
00:14:39.360 --> 00:14:45.679
It moves this from an interesting association to a potential mechanistic battery.
00:14:46.480 --> 00:14:48.879
Now what does that mean for treatment?
00:14:49.120 --> 00:14:52.320
What can we actually do with this information?
00:14:52.879 --> 00:15:00.799
This is where the research gets more cautious and where the science and the marketing begin to diverge.
00:15:02.480 --> 00:15:30.240
Probiotics and mental health the evidence and its limits systematic review and meta analysis BMC Psychiatry november twenty twenty five pre probiotics showed significant effects on anxiety and depression symptoms in a randomized controlled trials.
00:15:36.879 --> 00:15:52.240
The majority of recent literature suggests a beneficial role of probiotics in the treatment of depression and anxiety despite the existence of a substantial number of less positive findings.
00:15:53.120 --> 00:16:08.080
But the same reviews consistently note there is a lack of consistent findings, variability in treatment approaches and clinical presentations, limits the comparability and generalization of findings.
00:16:08.399 --> 00:16:23.679
The lack of standardization in dosing and strain selection in addition to the scarcity of large scale clinical studies limits the applicability of these findings in clinical therapy.
00:16:24.480 --> 00:16:38.320
Translation probatic so promising but inconsistent effects which specific strains at what dose for how long for which presentations these are not yet established.
00:16:40.080 --> 00:16:42.559
Promising but inconsistent.
00:16:44.240 --> 00:16:47.200
That phrase is doing important work.
00:16:47.679 --> 00:16:56.080
It is not a dismissal of the evidence, it is an honest description of where the evidence currently sits.
00:16:57.919 --> 00:17:02.480
The signal is real, the research is showing effects.
00:17:03.519 --> 00:17:19.279
But we do not yet know enough to say with confidence which probiotic in which dose for which person with which presentation for how long will produce a meaningful sustained benefit for depression or anxiety.
00:17:19.839 --> 00:17:35.440
And that gap between this is a real and seasonal, never good area of science, and by this specific supplement supplement and feel better is exactly the gap we examined across the last two episodes.
00:17:39.039 --> 00:17:42.720
So what can we reasonably take from all this?
00:17:43.359 --> 00:17:52.240
I want to be careful not to leave this episode in the same place that episodes six and seven ended with caution and critique.
00:17:52.720 --> 00:17:59.119
Because the gut-brain axis science genuinely offers something that is worth holding.
00:17:59.440 --> 00:18:02.079
The first thing is conceptual.
00:18:02.640 --> 00:18:08.640
Mental health is not just a brain problem, it is a whole body condition.
00:18:08.880 --> 00:18:19.599
The gut, the immune system, the inflammatory response, the vagus nerve, the microbiome, these are not peripheral to mental health.
00:18:19.839 --> 00:18:22.160
They are a part of its biology.
00:18:24.079 --> 00:18:29.200
That reframe has value independent of any specific intervention.
00:18:29.440 --> 00:18:37.279
It means that when we talk about mental health, we are talking about the whole body, not just what happens between the ears.
00:18:38.799 --> 00:18:41.680
The second thing is more practical.
00:18:42.079 --> 00:18:54.319
The research consistently finds that certain things support a healthy gut microbiome and the same things are independently associated with better mental health outcomes.
00:18:55.839 --> 00:19:03.279
What consistently supports the gut brain access current evidence?
00:19:04.240 --> 00:20:21.599
Well established, consistent across multiple studies, dietary diversity, wide variety of whole foods, fibre intake feeds SCFA producing bacteria, fermented foods, natural probiotics, yogurt, kefir, kimchi, sauerkraut and miso, reduced ultra processed food intake, UPF associated with increased risk of common mental disorders, umbrella review 2024, physical exercise directly modulates microbiome composition and independently of support mood, reduced antibiotic overuse, preserves microbiodiversity, emerging, promising but not yet established as clinical guidance, specific probiotic strings, particularly lactobacculus, vividobacterium species, prebiotic supplementation, fake or microbata transplantation FMT for depression, early human trials showing antidepressants effects.
00:20:23.519 --> 00:20:32.480
I want to sit with the ultra-processed food finding for a moment because it is one of the most robust in this area.
00:20:34.160 --> 00:20:48.960
A 2024 umbrella review, a review of reviews, found a consistent dose response association between ultra-processed food intake and risk of common mental disorders.
00:20:49.759 --> 00:20:55.359
Dose response means the more UPF consumed, the higher the risk.
00:20:55.920 --> 00:20:59.359
That is a strong epidemiological signal.
00:21:00.559 --> 00:21:04.559
It does not mean that ultra-processed food causes depression.
00:21:05.599 --> 00:21:09.039
The relationship is almost certainly bidirectional.
00:21:09.359 --> 00:21:13.920
Depression affects what people eat and what people eat affects depression.
00:21:14.160 --> 00:21:17.359
But the association is consistent and significant.
00:21:18.799 --> 00:21:22.319
And it points towards something accessible.
00:21:22.960 --> 00:21:32.000
Dietary choices that support microbiome health are also choices that the evidence independently associates with mental health.
00:21:40.960 --> 00:21:48.079
I started this episode with a fact 95% of the body's serotonin is produced in the gut.
00:21:48.880 --> 00:21:52.720
I want to close with what that fact actually means.
00:21:54.319 --> 00:21:59.839
It means that the separation between mind and body that had dominated her rethink.
00:22:00.240 --> 00:22:08.240
About mental health, the idea that depression is a brain problem with brain solutions is not the whole picture.
00:22:09.039 --> 00:22:24.079
Mental health is a whole body condition, the gut is involved, the immune system is involved, the inflammatory response is involved, what you eat, how you move, what you were exposed to in your life.
00:22:24.319 --> 00:22:29.839
These are not separate for your mental health, they are a part of its biology.
00:22:30.799 --> 00:22:34.799
That does not mean a probiotic will lift your depression.
00:22:35.359 --> 00:22:47.759
The research is not there yet, but it does mean that mental health is a more whole body question than the systems designed to treat it have historically acknowledged.
00:22:48.000 --> 00:22:53.359
And that framing that the whole body is involved is one worth carrying.
00:22:54.880 --> 00:23:07.920
Next episode, we are going to look at AI and mental health, what artificial intelligence is already doing in the mental health space and the particular dangers of using it to diagnose itself.
00:23:10.160 --> 00:23:12.240
But for now that's enough.
00:24:15.599 --> 00:24:21.039
You can call or text 988 the suicide and crisis lifeline.
00:24:21.200 --> 00:24:25.200
Free confidential available 24 hours a day.
00:24:25.519 --> 00:24:29.279
Or text home to 741 741.
00:24:29.759 --> 00:24:34.319
The Crisis Techline, also free, confidential, and available anytime.
00:24:35.440 --> 00:24:39.519
You can find this show wherever you listen to your podcasts.
00:24:40.400 --> 00:24:45.119
If today's episode meant something to you, please show it with someone who might need it.
00:24:45.599 --> 00:24:48.640
I'm Toman, I'll be back for episode nine.
00:24:48.880 --> 00:24:50.319
Take care of yourself.
00:00:03.200 --> 00:00:11.519
Approximately ninety-five percent of the body's serotonin is produced in the gut, not the brain, the gut.
00:00:12.720 --> 00:00:24.239
That single fact, which is well established, not contested, and has been known for decades, changes something about how we think about mental health.
00:00:25.280 --> 00:00:41.039
If serotonin is central to mood regulation and most serotonin is produced in the gut, then the gut is not just a digestive organ, it is a participant in your mental health.
00:00:42.320 --> 00:00:52.640
The question is what that means and the answer is more complicated, more interesting, and more uncertain than most of what you'll hear about it.
00:00:52.960 --> 00:00:55.840
Today we are going to go there.
00:01:20.719 --> 00:01:41.120
A podcast about mental health founded in science and I am Torin, not a therapist, not a clinician, someone who has spent 20 years inside these questions.
00:01:42.000 --> 00:01:45.439
And this is what happens when I ask them out loud.
00:01:46.480 --> 00:01:55.519
This episode is episode eight, and I want to prepare from the outset about what a kind of episode this is.
00:02:08.639 --> 00:02:24.719
The science here is real, substantial, and genuinely changing how we understand the relationship between the body and the mind.
00:02:28.479 --> 00:02:46.240
It is also one of the most heavily marketed areas in the biology industry, probics, psychobotics, methods, what the particles, the commercial ecosystem, and only science, is it enormous and learning.
00:02:49.039 --> 00:03:04.080
This episode is going to give you the after science, what the research is, I think it doesn't understand where the line sits between what we genuinely know and what is being shown on the basis of what we know.
00:03:15.599 --> 00:03:23.520
I want to start with something that many people who have lived with depression for a long time will recognise.
00:03:24.080 --> 00:03:26.400
The physical dimension of it.
00:03:26.639 --> 00:03:45.759
Not just the heaviness in the mind, the heaviness in the body, the stomach that doesn't feel right, the appetite that disappears or becomes relentless, the gut that seems to respond to emotional states before the brain has fully registered them.
00:03:47.120 --> 00:03:57.120
If you have noticed that your gut and your mood seem to move together, that anxiety lives somewhere in your stomach.
00:03:57.840 --> 00:04:07.199
That depression dulls your appetite, that certain foods change how you feel in ways that seem to go beyond digestion.
00:04:07.759 --> 00:04:10.080
You are noticing something real.
00:04:12.240 --> 00:04:20.079
The relationship between the gut and the brain is not a metaphor, it is a biological reality.
00:04:21.279 --> 00:04:28.720
And the research into it is one of the most exciting developments in mental health science in recent years.
00:04:29.920 --> 00:04:36.560
The question is what we can actually do with it, and that is where things get complicated.
00:04:40.240 --> 00:04:42.959
The usual frame before we go in.
00:04:44.079 --> 00:04:48.959
I am not a gastroenterologist or a microbiologist.
00:04:49.120 --> 00:04:57.120
Everything that I share today comes from published peer reviewed research sources are in the show notes.
00:04:58.720 --> 00:05:03.439
I want to hold the same standard I've held across the series.
00:05:03.839 --> 00:05:06.639
What is then established I'll say so.
00:05:07.600 --> 00:05:16.480
What is emerging and promising or name it as that, what is contested or clear, I'll say that too.
00:05:17.360 --> 00:05:29.439
This episode covers four things first what the gut of brain access actually is and how the communication between them works.
00:05:32.079 --> 00:05:40.160
Second, the serotonin question what the gut has to do with it and what that means for mental health.
00:05:41.199 --> 00:05:50.800
Third, what the research on probiotics and the gut microbiome actually shows for depression and anxiety.
00:05:51.199 --> 00:05:59.360
Fourth, what we can reasonably take from all of this and where the honest limits of that are.
00:12:28.799 --> 00:12:32.720
Which leads us to the microbiome itself.
00:12:37.759 --> 00:12:51.919
The gut microbiome is the community of trillions of microorganisms living in the digestive tract, bacteria, viruses, fungi, archaea, approximately 1,000 different species.
00:12:52.480 --> 00:13:01.120
Each person's microbiome is unique, shaped by genetics, birth, diet, medication, stress and environment.
00:13:02.799 --> 00:13:11.519
And the research connecting microbiome health to mental health is one of the most rapidly developing areas in all of medicine.
00:13:13.200 --> 00:13:18.240
Frontiers in Microbiology 2025 Systematic Review.
00:13:18.480 --> 00:13:33.600
Studies involving animal and human subjects suggest an association between gut microbial diversity and mental health, indicating that microbiota disturbances may contribute to depression onset.
00:13:37.919 --> 00:13:56.960
People with depression often show lower levels of SCFA producing bacteria, higher levels of pro-inflammatory bacteria, increased intestinal permeability, altered tryptophan metabolism.
00:13:57.440 --> 00:14:09.759
Early life stress causes significant changes in gut microbiome composition, and these changes appear to mediate some of the neuropsychiatric effects of that stress.
00:14:11.440 --> 00:14:16.799
That Mendelian randomization finding is particularly significant.
00:14:17.919 --> 00:14:21.360
Causative, not merely correlational.
00:14:22.480 --> 00:14:30.080
The microbiome dysbiosis appears to be contributing to depression, not just occurring alongside it.
00:14:35.440 --> 00:14:39.120
That is an important step forward in the science.
00:14:39.360 --> 00:14:45.679
It moves this from an interesting association to a potential mechanistic battery.
00:14:46.480 --> 00:14:48.879
Now what does that mean for treatment?
00:14:49.120 --> 00:14:52.320
What can we actually do with this information?
00:14:52.879 --> 00:15:00.799
This is where the research gets more cautious and where the science and the marketing begin to diverge.
00:15:02.480 --> 00:15:30.240
Probiotics and mental health the evidence and its limits systematic review and meta analysis BMC Psychiatry november twenty twenty five pre probiotics showed significant effects on anxiety and depression symptoms in a randomized controlled trials.
00:15:36.879 --> 00:15:52.240
The majority of recent literature suggests a beneficial role of probiotics in the treatment of depression and anxiety despite the existence of a substantial number of less positive findings.
00:15:53.120 --> 00:16:08.080
But the same reviews consistently note there is a lack of consistent findings, variability in treatment approaches and clinical presentations, limits the comparability and generalization of findings.
00:16:08.399 --> 00:16:23.679
The lack of standardization in dosing and strain selection in addition to the scarcity of large scale clinical studies limits the applicability of these findings in clinical therapy.
00:16:24.480 --> 00:16:38.320
Translation probatic so promising but inconsistent effects which specific strains at what dose for how long for which presentations these are not yet established.
00:16:40.080 --> 00:16:42.559
Promising but inconsistent.
00:16:44.240 --> 00:16:47.200
That phrase is doing important work.
00:16:47.679 --> 00:16:56.080
It is not a dismissal of the evidence, it is an honest description of where the evidence currently sits.
00:16:57.919 --> 00:17:02.480
The signal is real, the research is showing effects.
00:17:03.519 --> 00:17:19.279
But we do not yet know enough to say with confidence which probiotic in which dose for which person with which presentation for how long will produce a meaningful sustained benefit for depression or anxiety.
00:17:19.839 --> 00:17:35.440
And that gap between this is a real and seasonal, never good area of science, and by this specific supplement supplement and feel better is exactly the gap we examined across the last two episodes.
00:17:39.039 --> 00:17:42.720
So what can we reasonably take from all this?
00:17:43.359 --> 00:17:52.240
I want to be careful not to leave this episode in the same place that episodes six and seven ended with caution and critique.
00:17:52.720 --> 00:17:59.119
Because the gut-brain axis science genuinely offers something that is worth holding.
00:17:59.440 --> 00:18:02.079
The first thing is conceptual.
00:18:02.640 --> 00:18:08.640
Mental health is not just a brain problem, it is a whole body condition.
00:18:08.880 --> 00:18:19.599
The gut, the immune system, the inflammatory response, the vagus nerve, the microbiome, these are not peripheral to mental health.
00:18:19.839 --> 00:18:22.160
They are a part of its biology.
00:18:24.079 --> 00:18:29.200
That reframe has value independent of any specific intervention.
00:18:29.440 --> 00:18:37.279
It means that when we talk about mental health, we are talking about the whole body, not just what happens between the ears.
00:18:38.799 --> 00:18:41.680
The second thing is more practical.
00:18:42.079 --> 00:18:54.319
The research consistently finds that certain things support a healthy gut microbiome and the same things are independently associated with better mental health outcomes.
00:18:55.839 --> 00:19:03.279
What consistently supports the gut brain access current evidence?
00:19:04.240 --> 00:20:21.599
Well established, consistent across multiple studies, dietary diversity, wide variety of whole foods, fibre intake feeds SCFA producing bacteria, fermented foods, natural probiotics, yogurt, kefir, kimchi, sauerkraut and miso, reduced ultra processed food intake, UPF associated with increased risk of common mental disorders, umbrella review 2024, physical exercise directly modulates microbiome composition and independently of support mood, reduced antibiotic overuse, preserves microbiodiversity, emerging, promising but not yet established as clinical guidance, specific probiotic strings, particularly lactobacculus, vividobacterium species, prebiotic supplementation, fake or microbata transplantation FMT for depression, early human trials showing antidepressants effects.
00:20:23.519 --> 00:20:32.480
I want to sit with the ultra-processed food finding for a moment because it is one of the most robust in this area.
00:20:34.160 --> 00:20:48.960
A 2024 umbrella review, a review of reviews, found a consistent dose response association between ultra-processed food intake and risk of common mental disorders.
00:20:49.759 --> 00:20:55.359
Dose response means the more UPF consumed, the higher the risk.
00:20:55.920 --> 00:20:59.359
That is a strong epidemiological signal.
00:21:00.559 --> 00:21:04.559
It does not mean that ultra-processed food causes depression.
00:21:05.599 --> 00:21:09.039
The relationship is almost certainly bidirectional.
00:21:09.359 --> 00:21:13.920
Depression affects what people eat and what people eat affects depression.
00:21:14.160 --> 00:21:17.359
But the association is consistent and significant.
00:21:18.799 --> 00:21:22.319
And it points towards something accessible.
00:21:22.960 --> 00:21:32.000
Dietary choices that support microbiome health are also choices that the evidence independently associates with mental health.
00:21:40.960 --> 00:21:48.079
I started this episode with a fact 95% of the body's serotonin is produced in the gut.
00:21:48.880 --> 00:21:52.720
I want to close with what that fact actually means.
00:21:54.319 --> 00:21:59.839
It means that the separation between mind and body that had dominated her rethink.
00:22:00.240 --> 00:22:08.240
About mental health, the idea that depression is a brain problem with brain solutions is not the whole picture.
00:22:09.039 --> 00:22:24.079
Mental health is a whole body condition, the gut is involved, the immune system is involved, the inflammatory response is involved, what you eat, how you move, what you were exposed to in your life.
00:22:24.319 --> 00:22:29.839
These are not separate for your mental health, they are a part of its biology.
00:22:30.799 --> 00:22:34.799
That does not mean a probiotic will lift your depression.
00:22:35.359 --> 00:22:47.759
The research is not there yet, but it does mean that mental health is a more whole body question than the systems designed to treat it have historically acknowledged.
00:22:48.000 --> 00:22:53.359
And that framing that the whole body is involved is one worth carrying.
00:22:54.880 --> 00:23:07.920
Next episode, we are going to look at AI and mental health, what artificial intelligence is already doing in the mental health space and the particular dangers of using it to diagnose itself.
00:23:10.160 --> 00:23:12.240
But for now that's enough.
00:24:15.599 --> 00:24:21.039
You can call or text 988 the suicide and crisis lifeline.
00:24:21.200 --> 00:24:25.200
Free confidential available 24 hours a day.
00:24:25.519 --> 00:24:29.279
Or text home to 741 741.
00:24:29.759 --> 00:24:34.319
The Crisis Techline, also free, confidential, and available anytime.
00:24:35.440 --> 00:24:39.519
You can find this show wherever you listen to your podcasts.
00:24:40.400 --> 00:24:45.119
If today's episode meant something to you, please show it with someone who might need it.
00:24:45.599 --> 00:24:48.640
I'm Toman, I'll be back for episode nine.
00:24:48.880 --> 00:24:50.319
Take care of yourself.
