Recap: Simple steps to prevent allergies | Prof. Gideon Lack

Summary

Detailed Summary of "Recap: Simple Steps to Prevent Allergies | Prof. Gideon Lack"

Podcast: ZOE Science & Nutrition
Host: Jonathan Wolf
Release Date: August 5, 2025

Note: Although the episode title references Professor Gideon Lack and focuses on preventing allergies, the provided transcript centers on the gut-brain axis with insights from Professor John Kryan. This summary reflects the content of the transcript.

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Introduction to the Gut-Brain Connection

Time Stamp: [00:01] - [00:51]

The episode begins with an introduction to the intricate relationship between the gut and the brain. For years, the brain was perceived as an isolated organ, functioning independently from the rest of the body. However, emerging research challenges this notion by revealing that the gut acts as a "second brain," influencing various aspects of our mental and physical health, including mood, memory, and neurological disease risk.

Exploring the Microbiome's Impact on Brain Function

Time Stamp: [00:51] - [03:40]

Host (B): Asks about the links between the gut and the brain.
Professor John Kryan (C): Explains that over the past two decades, substantial evidence has emerged showing that the gut microbiome significantly influences brain development and function. Most of this evidence comes from animal studies, particularly involving mice and rats. By studying germ-free mice—those raised in sterile conditions without any microbes—researchers have observed abnormal brain development, highlighting the microbiome's crucial role.

Key Quote:
"Mice that have grown up without any bacteria in their gut, their brains don't develop normally."
— Prof. John Kryan [01:17]

Understanding the Gut-Brain Axis

Time Stamp: [03:40] - [06:22]

Host (B): Seeks clarification on the term "gut-brain axis."
Prof. Kryan: Describes the gut-brain axis as the communication pathway between the gut and the brain. Traditionally, this axis was studied concerning food intake and hunger signals. However, recent studies incorporate the microbiome as a pivotal player, adding complexity to our understanding. The microbiome has always been integral to human physiology, influencing various bodily functions and behaviors through evolutionary interactions.

Key Quote:
"Our microbiome could play such a key role in so many aspects of our physiology and our behavior."
— Prof. John Kryan [05:56]

Mechanisms of Communication Between Gut and Brain

Time Stamp: [06:22] - [08:26]

Host (B): Asks how tiny bacteria in the gut can influence the brain located elsewhere.
Prof. Kryan: Outlines the primary mechanisms:

1. Enteric Nervous System: Often referred to as the "second brain," it contains more nerve cells than the spinal cord and serves as a conduit for signaling between the gut and the brain.

2. Vagus Nerve: A major cranial nerve that facilitates communication between the gut and the brain. Prof. Kryan references a study where cutting the vagus nerve in mice nullified the behavioral effects of certain gut bacteria, emphasizing the nerve's role in gut-brain communication.

Key Quote:
"When you cut the vagus nerve in a mouse model, we severed all of the effects of a specific Lactobacillus bacteria on brain and behavior were gone."
— Prof. John Kryan [07:45]

Practical Steps to Support Gut-Brain Health

Time Stamp: [08:26] - [12:55]

Host (B): Inquires about actionable advice for listeners to support their gut-brain axis.
Prof. Kryan: Suggests several evidence-based strategies:

1. Dietary Enhancements:

   • Prebiotics: Increase fiber intake to nourish beneficial gut bacteria.
   • Fermented Foods: Incorporate kimchi, kefir, kombucha, and other fermented products to introduce beneficial microbes.
   • Polyphenols: Consume foods rich in polyphenols like onions, grapes, nuts, green tea, and grape juice, which support microbial health.
   • Polyunsaturated Fatty Acids (PUFAs): Include sources like fish oils and certain plant-based oils to benefit both cellular function and the microbiome.

2. Dietary Avoidances:

   • Processed Foods and Artificial Sweeteners: Limit consumption as they negatively impact the microbiome.

3. Lifestyle Factors:

   • Sleep and Circadian Rhythms: Maintain regular sleep patterns to support microbial health.
   • Exercise: Engage in aerobic activities, which have been shown to positively influence the microbiome.
   • Mode of Birth: Advocate for natural birth when possible, as C-sections can have long-term effects on the microbiome.

4. Social and Environmental Factors:

   • Pet Ownership: Having pets, especially dogs, can benefit the microbiome, potentially improving behavior through gut-brain signaling.

Key Quote:
"We know that your microbiome changes as you navigate life naturally... we need to mind our microbes for optimal brain health."
— Prof. John Kryan [09:30]

Specific Considerations for Different Life Stages

Maintaining Brain Health in Older Age

Time Stamp: [11:48] - [12:55]

Host (B): Asks about strategies for maintaining brain health as one ages.
Prof. Kryan: Highlights the importance of dietary diversity, particularly Mediterranean-style diets, which support microbial diversity and, by extension, brain health. While pet ownership has shown benefits in early life, its effects in older adults require further research. Social interactions also play a role in maintaining a healthy microbiome in older age.

Key Quote:
"Diversity in the diet is what gives the best health outcomes in the context of frailty and other medical outcomes."
— Prof. John Kryan [12:09]

Gut-Brain Axis During Adolescence

Time Stamp: [12:55] - [13:28]

Prof. Kryan: Briefly touches on adolescence as a critical period for brain development, involving significant neural pruning and decision-making processes that could be influenced by the microbiome. However, the transcript ends before elaborating further.

Conclusion

The episode underscores the profound impact of the gut microbiome on brain health, emphasizing the importance of maintaining a healthy and diverse microbiome through diet and lifestyle choices. By understanding and supporting the gut-brain axis, individuals can potentially enhance their mental and physical well-being across various stages of life.

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Notable Quotes Summary:

1. "Mice that have grown up without any bacteria in their gut, their brains don't develop normally."
   — Prof. John Kryan [01:17]

2. "Our microbiome could play such a key role in so many aspects of our physiology and our behavior."
   — Prof. John Kryan [05:56]

3. "When you cut the vagus nerve in a mouse model, we severed all of the effects of a specific Lactobacillus bacteria on brain and behavior were gone."
   — Prof. John Kryan [07:45]

4. "We know that your microbiome changes as you navigate life naturally... we need to mind our microbes for optimal brain health."
   — Prof. John Kryan [09:30]

5. "Diversity in the diet is what gives the best health outcomes in the context of frailty and other medical outcomes."
   — Prof. John Kryan [12:09]

Transcript

[A]

Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Today we're exploring the connection between your gut and your brain. For years, the brain was seen as somewhat detached from other parts of our body, working in isolation above all else. However, emerging research is flipping our idea of the brain on its head. Scientists now know that the gut acts like a second brain, influencing everything from our mood and memory to our risk of neurological disease. So have we been neglecting a vital piece of the brain health puzzle? Joining me to unpack this topic is Professor John Kryan, a world leading expert in the gut brain axis. He's here to explain how the two communicate and what you can do to support that connection.

[B]

Are there links between the gut and the brain?

[C]

What we know now, and there's been an evolution over the last two decades, I would say, is that there is now concrete evidence that the composition of the microbes in your gut influences brain development, influences brain function, and can help steer the brain in specific ways. The evidence is coming largely from studies in animal models.

[B]

And John, just to make sure, everyone has said an animal model, what does that mean?

[C]

Usually a mouse or a rat. So because we can get mice that can grow up without microbes ever having a microbe, you know, if you want to find out if something is important in a process, we know from engineering or other areas of biology that if you take it out and see what happens, it's probably one of the best ways to see if it's important. So mice that have grown up without bacteria, they allow us to answer the question, is the microbiome relevant? Yes or no. And studies from our lab and from other labs over the past decade or more have shown that in these mice that grow up without any bacteria in their gut, that their brains don't develop normally.

[B]

That's amazing. And do you find special mice that you found somewhere in the world that grew up without any gut microbiome? Is that how you compare this?

[C]

No. This is an unusual lab based situation. So these animals are kept in this ultra sterile condition where they've never been exposed to microbes. And this concept goes back to Louis Pasteur. He first tried to do these work with these types of mice and they are not really translatable to anything human, with maybe the exception being the boy in the bubble that Paul sang about in the 1980s. These mice in the bubble, they allow us to have this specific question, is the microbiome involved? Yes or no?

[B]

Got it. So it's quite unnatural, is what you're saying. You have to create this incredibly sterile situation because we're constantly surrounded by these bacteria who want to get into us and presumably these mice. So you create this incredibly sterile situation to discover what happens if a mammal grows up without any bacteria. And that's what you're comparing then with the normal situation for mice and I guess for us. Right, which is we're stuffed full of trillions of them.

[C]

Absolutely. And our group and the group of Rochelle Heights in Karlinska and Jane Foster in McMaster well over a decade ago, all showed roughly around the same time, that these mice have messed up brains in different ways in terms of their behavior. They respond differently to stress. We showed that they don't have proper social behavior, that they don't have proper fear learning, and their pain processing is different. So they've given us a real entry point into convincing us that there's something about microbes and brain function that we need to pay more attention to. And that's taken us on this journey that my lab has been on for well over a decade.

[B]

And, John, one of the words that I think we often hear is like gut brain axis, which is a great sort of phrase, which I don't really understand what it is, but I'm hoping you're about to explain. Is that this or is that something different?

[C]

Well, yeah. So the gut brain axis has been long, long known. It's basically how signals from your gut go to your brain to change your behavior. Now, that's been very well studied in the context of food intake, because we take food into our bodies, but the reason we do that is in response to hunger. Signals that come from our brain, and then we take it in, and then we stop eating based on signals that are telling us we're full, and they are also brain derived. And so the gut brain axis has been around for a long time, mainly in that context. Then people started being more understanding that disorders like irritable bowel syndrome, which is a very common unloved disorder associated with abdominal pain and bloating and various other functional side effects, that this is really a disorder of how our gut and our brains talk to each other. What we now think of is a microbiome, gut brain access. So the microbes are the new players. So it makes things even more complex. And what we're trying to do figure out is how do the microbes in the gut talk to the aspects of gut brain signaling to change brain and behavior? So it's a new dimension, a new Player, if you will. We have to think that the microbes were there first. And so that's an important aspect of all of this in our learnings from an evolutionary perspective, microbes were there. And so there's never been a time where our brain or our gut existed without microbial signals. So we kind of have to contextualize that. And we, we're very human focused in our primacy of what's the most important. But we have to remember also that the mitochondria, the powerhouses of cells, are actually microbes that got lost into the cells. And so there's such a close relationship between our microbes and everything through evolution. And so once you start contextualizing it in that way, it's probably not surprising that the microbiome could play such a key role in so many aspects of our physiology and our behavior.

[B]

So just to make sure I got that, what you're saying is, hey, the microbes were there before there were any human beings, in fact, before there were any mammals. And so, you know, even from the very beginning of building this gut, there would have been microbes there. So it's hardly surprising that they are a sort of built in feature, if you like, of our body rather than how, you know, I think we obviously all thought about them until a few years ago as a sort of in irrelevance.

[C]

Yeah, absolutely.

[B]

So I think lots of listeners have asked this question about, well, how does that work? Because I think they can understand that your microbes affect the way you digest your food. They're in the same place. That makes sense. But you know, my gut and my brain are in two different places. Bacteria are really small. How do these bacteria affect what's going on in my brain? And I know this is something that you study.

[C]

Yeah. And it's a large part of what our lab is focused on is really trying to delineate the mechanisms and pathways for this communication. And there are a number of ways. First of all, it's worth noting that within our gut we have a second brain. This is called the enteric nervous system. And this second brain has more nerve cells than our spinal cord. Enteric nervous system is very important for digestion, motility, various aspects of gut function. But it's also a really good conduit for signaling directly to the brain. So that's an important first pass on it. The second thing is we have a nerve. It's one of the major cranial nerves which sends signals from the brain to all the organs and from organs back up to the brain. It's called the vagus nerve. Now, vagus comes from the Latin for wandering. It's the same derivation as vagabond or vagrant. And this nerve is really well, poised to be an important highway of communication between the gut and the brain and between the microbes and the brain. And so over a decade ago, we showed together with the late John Beanstalk's lab that when you cut the vagus nerve in a mouse model, we severed, all of the effects of a specific Lactobacillus bacteria on brain and behavior were gone. So, as I like to remind people, this tells us that what happens in Vegas doesn't just stay in Vegas, but will actually affect our emotions in certain ways.

[B]

Okay, I love that. So I've got a vagus nerve inside me, which bit like Vegas, all sorts of bad things can happen and come back to haunt me afterwards. How would you think about what people should be doing either for themselves or as they're thinking about their children or. Or relatives?

[C]

The important thing is to realize that your microbiome changes as you navigate life naturally. There's a natural change overall. In early life, it takes about two years for stability to start to come in. And it's really primed to maximize what it can get from milk overall and then into adolescence. There's less studies, but we're beginning to see more and more relationships between the microbiome and then we get a stable microbiome unless we shift our environment. And then as we age, then we see a deleterious effect of aging on the microbiome, which we've been showing, for example, that that affects brain health. So we've been able to take the microbes from young animals and reverse the effects of aging on brain health. And that's been quite remarkable. So we know that we need to mind our microbes for optimal brain health. And so some of the practical things that I would tell people to do, that has some evidence, although we could do it more. So there are certain things to enrich in your diet, which is increasing the levels of prebiotics. Fibers in particular will be really, really important. Fermented foods, the 3Ks of kimchi, kefir and kombucha, but there's loads of other fermented foods. And throughout the world, we have a rich cultural history of fermented foods. And not so much in Ireland, I would say, but in other places. But studies like from Justin Sonnenberg's group and now more recently from our own, has shown that there's a science of biology, how these fermented foods are interacting with the hosts to have positive effects. So really, really doing that. We know color is great. Polyphenols give lots of foods color. And polyphenols are broken down by microbes, but they also act on microbes and they can be broken down to chemicals that will be really important. So heavily present in things like onions and grapes and nuts and also in green tea. And people often talk about it in the context of red wine, of course, but it's also in grape juice. But polyphenols are really good. There's been an increasing interest in polyunsaturated fatty acids. So These are the PUFAs that are very good for how membranes and cells work, but they also can have effects directly on the microbiome. And so maybe some of the positive effects of these polyunsaturated fatty acids may be really good. And then there are things we should avoid in our diet as much as we can, and that's the processed food. Artificial sweeteners in particular have been shown to have consistently negative effects on the microbiome. Overall. We know that certain lifestyle other factors can influence the micro microbiome. So our sleep and our circadian rhythms and jet lag all has effects. So we need to be careful on that. Exercise in particular, aerobic exercise has been shown to have really good effects on the microbiome and potentially then onto brain function overall mode of delivery at birth. So we should as a public health should be really encouraging more people to if they can give birth naturally as opposed to by C section because there's enduring effects of C section on the microbiome that can potentially translate to behavior in later life. And then finally there's great data now accumulating from population wide studies that having a pet and particularly a dog is good for your microbiome. And probably maybe some of the beneficial effects of companion dogs on behavior may be related to their effects on the microbiome and gut brain signaling. That needs to be figured out. But I think it's really intriguing area overall.

[B]

I just want to pick up on this sort of older age thing. So if you're listening to this and you want to maintain your brain health, which I think is becoming increasing focus for many people, right as we age and we see all of these problems. Is there anything specifically within that or on top of that that you need to do, should they all be immediately going out and getting a pet, is that the key additional activity?

[C]

Well, it's interesting. A lot of the pet work is coming from early life studies. So there hasn't been much data that I'm aware of in older people right now. And we know that social interactions themselves. By living with someone else, your microbiome starts to shift and change. The best studies on old age then have shown that things like the diversity in the diet is what gives the best health outcomes in the context of frailty and other medical outcomes. There's been no reasonably good data yet on brain function as we age in humans. But the studies like the New Age study and the elder Met studies, which would really support this increase in diversity of foods and Mediterranean style diets are really good for your microbes, so therefore they should be also good for your brain.

[B]

That makes sense. And what about adolescence? I think you talked about like a big shift going on in the brain at this point.

[C]

So the adolescent brain is really a brain that's still under construction. We often forget that our brain goes through quite remarkable changes during this period. And basically it's a period where the brain has to decide what to keep for the rest of life. So there's a lot of what we call pruning. So synaptic pruning, where basically our immune cells are saying, okay, keep or not keep. What's going to be essential for what need to keep you going?

[A]

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[B]

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[A]

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