Beyond Digestion with Dr. Karen McCarthy

Beyond Digestion: The Gut-Brain Axis, Leaky Gut, And How Your Microbiome Fights Chronic Disease [Part 1] With Dr. Karen McCarthy

Welcome to the show. We are back for another fun episode. I am Dr. Anna Marie, and with me is my mom, Dr. McCarthy, with decades of experience, and back for another episode. In this series, we are actually going to be talking all about gut health, which I am really excited about because it is just such an important topic, and I think so many people do not know how important it is and everything that it can affect. As always, this show is not medical advice. This is for educational purposes only, but welcome, Dr. McCarthy. I am so excited you are back again.

This is a great topic. 

I do not know if you want to do a little intro again. I know some of our audience might have heard you on our other show or other episodes, but in case you have not, if you want to do a little intro.

I’m a board-certified internal medicine physician. I have been working as an internist for over 40 years now in private practice. Now that I continue after retiring from my paying job, I continue to run a medical clinic dealing with addiction and homelessness each week, which I really enjoy. It is very rewarding and trying to help those on the streets who are dealing with so many medical and psychological issues. 

Welcome. Lots of experience and still practicing, which is awesome. Let's get into this episode. We are really talking all about gut health. That is going to be our next series. Maybe just to start out. Let's maybe go over. It is a broad question, but what does gut health actually refer to?

Defining Gut Health And The Microbiome

Basically, by definition, gut health refers to how your digestive tract is working, especially whether you are having normal digestion and absorption and bowel function without ongoing symptoms like bloating, pain, irritable bowel symptoms, constipation, diarrhea. It includes a very important factor, the balance of microbes in your gut microbiome.

The microbiome is basically the live bacteria that are functioning in your intestinal tract, and they have such an important function, and if the balance of good and bad bacteria is off, it can wreak havoc on your health, not just gut health, as we are going to be finding out. It is these good gut microbiome help to digest your food and support gut health. In a healthy, normal gut, the cells that line your gastrointestinal tract maintain this tight junction that keeps the food and the protein fragments on the correct side inside your gut.

Molecules resulting from digestion, like amino acids from proteins, are broken down, and then they are transported into these gut lining cells, and from there they go into the bloodstream, which then carries all these nutrients to your body. The GI tract can become leaky, which we will go into at length here in this podcast, from something called gut dysbiosis, where the bad bacteria, dys, meaning bad, and bios, meaning the bad bacteria, overtake the good bacteria. 

I feel like it is interesting, the leaky gut, it has actually been around, people talking about it for decades, but it is really just in the last, I would say, ten years or so that it has been recognized more in our modern medicine, like GI professionals are recognizing it, and now we know it is a real issue.

Causes And Effects Of Leaky Gut (Gut Dysbiosis)

We are seeing it more even with, as we will go into here with changes in our intake of foods, like gluten, which has been modified is a real inflammatory agent that can accelerate this leaky gut and then as we go on later with toxins like microplastics and all the pesticides they really can destroy the integrity of this lining of the gut and then we are in big trouble. You can see chemicals also, even from what we were taking in, all of these soft drinks, alcohol, sugar, foods, processed seed oils are a big culprit, preservatives, inflammation, chronic stress, medications, even like antibiotics, and we are going to go into this again in this podcast or the next one.

Now it was reading that even aspirin and acetaminophen can have some disruptive function on the gut. A leaky gut, when it does occur, allows these fragments of bacteria and large protein fragments, not when they are broken down to little amino acids, but large protein fragments and partially digested food to leak out of your gut into your bloodstream. These fragments are then recognized by our immune system as foreign invaders and trigger this inflammatory cascade. We know that the GI tract, once it is in this inflammatory state, causes so many diseases.

It is important to keep these large protein fragments from leaking out of the gut and into the bloodstream. Again, it revs up your immune system because it sees it as an invader. We are seeing that this could be causing autoimmune conditions, which are diseases like lupus, where your body does not recognize part of itself like it should normally. Basically, your body is attacking itself. There are so many different immune conditions, but the body is attacking itself.

The Gut-Brain Connection And Chronic Inflammation

We will see it in rheumatoid arthritis, lupus, and even multiple sclerosis. We are seeing from this chronic inflammation, and of course, as we went over in our last podcast about Alzheimer's and dementia, that we know it also causes chronic inflammation in the brain cells and that contributes to Alzheimer's because that gut-brain connection is really important.

Bacterial products like the gram-negative endotoxins, gram-negative just means it is a type of bacteria, gram-negative bacteria that produce these toxic chemicals called endotoxins, and they can even influence our mood and cognitive function. This research suggests that if we can modify microbial ecology, it can have beneficial therapeutic effects. Again, gut dysbiosis also alters from our last episode, your blood-brain barrier. Not only do you have a protective barrier in the lining of your gut, but you also have a protective barrier to protect the brain.

It is called the blood-brain barrier. We know that this gut dysbiosis can create neuroinflammatory pathways linked to Alzheimer's, Parkinson's disease, and multiple sclerosis. There is a lot of emerging research being done on the benefits of a healthy gut releasing beneficial short-chain fatty acids, which we will go into, and that these are then transmitted via the vagus nerve from your gut to your brain, and these fatty acids include butyrate, propionate, and acetate.

Let's, I guess, go into a little bit about short-chain fatty acids. How do those affect the gut? 

These short-chain fatty acids, when we eat fiber, the colon bacteria fermented into these beneficial, healthy bacteria in your colon, will ferment it into these beneficial short-chain fatty acids, which some of them are the butyrate, propionate, and acetate. These bind to receptors in other organs of our body, like muscle, liver, and fat tissue, affecting the secretion of these gut hormones and peptides that are related.

We are finding out about our appetite, inflammation, energy expenditure, and fat oxidation. In episode two of this, I can go into more detail, but butyrate is such a beneficial small-chain fatty acid that supports not only the integrity of your gut lining, but also fighting cancer, promoting inflammation, and killing off really bad bacteria. It also protects against obesity and diabetes, acts as a prebiotic, and it is what feeds your colon cells. Butyrate is a small-chain fatty acid that actually gives nutrients to your colon cells. It is the primary energy source for colonocytes.

We know that it helps reduce inflammation, strengthens your gut barrier, and supports your immune system. It is a very important short-chain fatty acid, and I have more on hopefully if we have time on episode two, but in summary, then that gut health a healthy gut means your digestive tract is functioning normally with your normal gut microbiome in a balanced state, which is really rare to find in most individuals eating the Western diet. We have probiotics. 

Tweet: A healthy gut means your digestive tract is functioning properly, with your gut microbiome in a balanced state.

That is what I am going to ask. I feel like everybody talks about you know, they know of probiotics a little bit, but I think a lot of people do not know, actually, fully what they are. Also, people are talking about prebiotics more. I think yes, that would all be good to get into. 

Let's do that because I broke them out.

Maybe first is just what probiotics are?

Probiotics, Prebiotics, And Postbiotics Defined

Probiotics are live microorganisms, usually bacteria or yeast, that can provide health benefits when taken in adequate amounts. We really see high concentrations of them in fermented foods and high fiber foods, and they really help to support digestion and reduce GI inflammation and symptoms. That is basically what we see with probiotics, and there are so many different ones on the market.

I mentioned last time that the best way to do it is through your diet to get healthy probiotics. If you need a probiotic supplement, then I recommend the bacillus spore probiotic only because that bacillus spore probiotic does not get broken down by the acid in the stomach, and a lot of these probiotics, you know, they really have low absorption and assimilation, so that one is at least protected with the covering, you know, the spore covering. It quickly will help these other bacteria to survive. 

We will talk about I think some of the foods, too, because I think that is very important for people to get from probiotics.

That is the best way.

Also, I think people get probiotics and prebiotics kind of mixed up. What are prebiotics? 

Probiotics are basically what probiotics are. Prebiotics are foods, usually non-digestible fibers, that feed beneficial gut bacteria, gut microbes. Common examples will be inulin, which is in Benafiber and some of these other fiber sources, and then also fructooligosaccharides. Those are foods that, again, have high fiber content, which feed the beneficial bacteria. I look at it like a fertilizer to allow the good bacteria from probiotic intake to really populate and overtake the bad guys. Prebiotics are really important, we are finding out. We will go into some other health benefits too on that.

Some people have to talk about postbiotics.

That is a new one that they are using in a lot of research, too, but postbiotics are just beneficial compounds made when gut microbes break down prebiotics or otherwise metabolize food. These are just beneficial compounds, and they do include postbiotics, including those short-chain fatty acids that I was discussing earlier, like butyrate, and they also include enzymes and other bioactive substances that can help support the gut barrier and reduce inflammation. A good way to look at it, a simple way for the layman to see this, is to think about probiotics as the live workers, prebiotics are their food, and postbiotics are some of the useful products that they make. That is why diets rich in fiber and fermented foods are often linked with better gut support.

Tweet: Diets rich in fiber and fermented foods are often linked to better gut health.

Best Food Sources For Probiotics And Prebiotics

I like that analogy. They are definitely all related, right? You need the workers, so like the actual live, you, but then you also need the food for them to eat. The supplies for them to use so that they can make these beneficial products. That is a great analogy. I guess something that would be important is, like, where would you say the best foods are? Let's start with probiotics, like what would be the best food sources?

Probiotics again are those live beneficial. The best sources are yogurt with live cultures, which I am going to go into in episode 2 with Dr. Davis. Yogurt, which is really good for SIBO. We will get into that later. Base best food forces. Our yogurt, kefir, sauerkraut, kimchi, miso, Tempeh, kombucha, and some cheeses and fermented pickles.

Mostly fermented food is what it is like.

Yes.

What about prebiotics?

Prebiotics would be your fibers that feed your good gut bacteria, and those sources are onions and garlic, leeks, asparagus, Jerusalem artichokes, chicory root, oats, barley, bananas, apples, beans, lentils, peas, flaxseed, and some whole grains.

That is a lot. I guess postbiotics, you really would not get it from anywhere other than eating those first two, because then they would produce the postbiotic.

Yes, correct. They do have some research, though, on some beneficial compounds. Of course, they are made by, as you said, the beneficial microbes in your gut. They are not usually foods in the same way that these probiotics and prebiotics are, because they are mostly made in your gut when you have a healthy gut flora that ferments prebiotic fibers. I had a list too of some food examples that you could try, but say if you want to start this, you could start with your probiotics by eating yogurt, at breakfast, kefir in a smoothie, or kimchi or sauerkraut as a side, and then some miso and soup.

For your prebiotics, you could eat oats with banana and flaxseed, onions and garlic, and when you are cooking and I would say get fresh not the stuff that is canned in the garlic and then beans or lentils in your salads and soups and asparagus as leeks as your vegetables and then just you will then as a result of all of that eating get some good healthy post biotics. Is that a little bit of a helper there for you?

Fiber's Importance For Gut Health And SCFA Production

Yeah. It is mostly remembering those probiotics, like the yogurt, the kefir, and the kimchi, all of those foods that are fermented and then high fiber, which I do think people underestimate how important fiber is. I do think, especially in our diet. Protein is getting like such a hot topic now, but I think people are forgetting how important fiber is, and it really has such a huge impact on health.

I do think that protein is important too, but my concern is that so many people are now forgetting about fiber, right? They are only focusing on protein. Overall, if you look at our diets, most people are actually probably getting enough protein, but they are probably not getting enough fiber, which is so important for all of this. Let's see. We were talking before about some of the small-chain fatty acids. Let's maybe get into that for gut health. 

We would see the small chain fatty acids. Let’s see if I finish up on this one with you. I guess we could also see that these small chain fatty acids, again, remember the main one that I am going to be talking more about is butyrate, but let's just have an overview of their importance are that these small chain fatty acids are microbial metabolites. That is a good way to look at it. They are a breakdown food. Small-chain fatty acids are emerging now.

It is so amazing how much you were reading about small chain fatty acids, especially butyrate, as these key mediators in our diet and our health. Some of the evidence I can list here is that these small chain fatty acids are linked to reducing inflammation and improving insulin sensitivity. Gut-derived metabolites, these small-chain fatty acids may influence gut-brain access with implications for not only acuity, mental acuity, but also your moods. That is significant.

We are seeing this in psychiatry, even. We know that dysregulated metabolites that do not have high concentrations of these good small-chain fatty acids, they are often associated with inflammatory bowel disease, obesity, and again, neuropsychiatric conditions. Fiber fermentation is, like you said, so important to produce these small-chain fatty acids like butyrate and improve and heal a leaky gut. The gut barrier integrity and immune regulation are normalized. Of course, they do also, we know, reduce inflammation and improve insulin sensitivity because pre-diabetes and diabetes are all triggered by insulin resistance, and these small-chain fatty acids improve that. 

Just to review, so people understand and correct me if I am wrong. This is basically produced by the fiber fermentation. Again, by these probiotics, like when you are taking in probiotics naturally with fermented food. It is one of the ways these probiotics also work. It is really interesting that the many pathways that we are finding that this has a huge effect.

As I said, it is also the main food supply these small chain fatty acids are the main food supply for your colon cells, and so if they start starving, they can cause a lot of trouble, even as we are seeing with cancer triggers.

The Gut-Brain Axis And Neuropsychiatric Conditions

Colon cancer is on the rise, and it would be hard to think that some of it is not related to our diet, so it would make sense. It is always hard to prove causation versus correlation, but I mean, just going through that pathway, it does make sense. Can you kind of go over a little bit about the gut-brain axis? That is something that really has emerged in the last decade of how wild it is, this whole connection between what goes on in your gut and what goes on in your brain. 

Again, this started way back when in the pediatric arena with children with ADD, and some of these psychiatric difficulties, and Campbell McBride started realizing that the importance of what is in the gut can affect the brain. We know that the brain and intestines are closely connected by the vagus nerve, and that is part of your brain gut access. There is so much communication that we do not realize how much communication is done by nerve pathways, obviously, hormonal pathways, and immune pathways.

Now they are showing so much interaction with intestinal bacteria, which actually, on their own, have signaling molecules. The intestinal bacteria that are found regulate the brain and behavior. It can be a trigger for ADD, insomnia, anxiety, depression, bipolar affective disorder, and other psychological issues. That is why at the clinic I run downtown, I have them all on a probiotic, prebiotic. At least it is a little bit of help. I know the diet is not so great. We know that gut dysbiosis or bad bacterial overgrowth in the intestinal tract causes the leaky gut, thereby letting these toxins get into the bloodstream that we discussed earlier.

Tweet: Gut dysbiosis—an overgrowth of harmful bacteria in the intestines—can lead to leaky gut and widespread inflammation.

This also causes the blood-brain barrier that protects your brain tissue to also become compromised from leaky gut because of all those inflammatory chemicals that are coming through, and then instead of having that protective blood-brain barrier with its integrity, you get a leaky blood-brain barrier. That has been implicated in increasing amyloid, beta, and tau proteins. Those are the main proteins that are laid down for developing Alzheimer's. That is not a good thing.

We talked a little bit on our whole dementia prevention podcast and everything about how that is so important. It really does have a huge effect. 

The other one I have been reading about, and I am sure you have heard this too, is the periodontal disease caused by bacteria in the mouth called Porphyromonas gingivalis, which increases inflammation in the brain and triggers dementia. Just a healthy gut flora, even in the mouth, through the intestines to the end, which is part of your gut flora and is important for brain health. It is also important for our dental and oral health.

I honestly think so many people underestimate how important oral health is, because we already know that it increases even your cardiovascular health, which is just overall inflammation. Inflammation then begets inflammation. A lot of people forget how important that you actually have a whole microbiome that is in your mouth, that is in your teeth. There is a lot of stuff in terms of what we eat and drink that gets that all out of whack. That is where it starts. It is not surprising that it would also have an effect on the brain.

If time permits, and podcast who we are going to go over some of the benefits then of having a healthy oral microbiome population, and when you do not have it what it can it is amazing what it can cause, as you said, it is a lot of it is just this horrible inflammatory state in multiple areas of your body. We do know, though, that as time goes on, we are finding out more and more. I do suggest even for the mouth, like, and we will go into it in the next episode, but like when people gargle with Listerine, which kills a lot of the good bacteria and has been causing some problems.

I do suggest doing a coconut pull, where you swish the coconut oil around between the teeth, it gets them white and does a good job in restoring the normal oral flora. You can even get probiotic toothpaste now. I do not know if that will do the trick. Just trying to go more natural. Now I just ordered an electric toothbrush that does not have plastic bristles. Plastic bristles or nylon bristles. That is a Petro company byproduct. We were able to find one that is made from bristles that are made from castor oil bean. All natural, and then the handles are bamboo.

They are starting to make more, which is really exciting. I do think people do not realize a lot of those mouthwashes, like Listerine, how they can really mess up your mouth health, and then how it has an effect. I would have to double check on this, but I think Listerine is actually one there. There is like a lawsuit that is out for them because there is like a concern that it may be increasing the colon cancer risk.

Yes, and esophageal. I think you are correct.

How Gut Dysbiosis Affects Overall Health (Fatty Liver, Obesity)

It is just thinking about something that probably a lot of people do not realize how, but that shows how it can affect the rest of your gut and everything. How else would you say gut dysbiosis affects our health?

On its own could be like a hundred podcasts, but I am just going to mention a few. There should be a branch of medicine, not just GI, but another branch of medicine, a specialty on gut health. That is how important it is. One of them I was just recently reading about is this fatty liver causing leaky and leaky gut connection. Leaky gut is causing the fatty liver. Small intestinal bacterial overgrowth has been associated with fatty liver disorders. We know, and we are going to go into what SIBO is. 

Small Intestinal Bacterial Overgrowth (SIBO) Defined

Just so you do not, for those of you who do not know, Small Intestinal Bacterial Overgrowth is also called SIBO. If you hear that, it is the same thing.

It is basically the bad bacteria, not just being in your colon. It is specifically the bad bacteria in your small intestines, which we have a lot of people in this country eating the western diet, who have some degree of SIBO. Anyway, the metabolic dysbiosis and leaky gut have increased these circulating bacterial toxins, and one of them is called LPS. Those are endotoxins from these bad bacteria growing in the GI tract. They have also elevated the intestinal permeability, leaky gut, as measured, and they usually measure that by a chemical called zonulin.

All that to say, when you have this bad bacteria growing in the intestinal tract, it has been associated with this compromised intestinal permeability, which leads to fatty liver. That is one of them. Just to put a few of them in here. ADHD, we went over some of these psychiatric conditions. Generalized anxiety disorder, depression, autism, learning disabilities, obesity, pre-diabetes, metabolic syndrome, and Parkinson's disease. These are just a few of the conditions found to be very much influenced by your gut microbiome.

I am going to go into some of these toxins, but we know that even that herbicide glyphosate in Roundup triggers this zonulin, which measures how much of a leaky gut you have, and gluten does the same thing, so we are going to go into depth about that, too. Those two are the most powerful triggers of this zonulin release. It is that modified gluten that occurred in the 60s. The other thing if you look at a chart, obesity rates have continually started to climb from the 1960s to the current time. We did not use to have this much obesity and diabetes, but what was introduced in the 60s?

We had microplastics, which we will go into, and these modified grains, all causing an inflammatory state, gut dysbiosis, and real big problems on our metabolic health with diabetes and so forth. That is just touching the surface there. We know that as the process worsens with this gut dysbiosis, you get more production of pro-inflammatory cytokines, interferon, gamma, and even something called tumor necrosis factor.

These cytokines then start this vicious cycle. They actually further worsen the permeability. It is a chronic inflammatory disease, and with that dysregulation and that pathway occurring, which has been implicated in causing these autoimmune diseases, such as celiac disease, type 1 diabetes, inflammatory bowel disease, multiple sclerosis, and ankylosing spondylitis. 

The Epigenetic Effect Of Gut Dysbiosis On Gene Function

A lot of people you know do not realize that, so you have your genes right, so yeah, you have a genetic profile, but those genes usually have to be triggered. They are triggered to turn them on, and people who are predisposed to this get all of this inflammation that continues a cycle of inflammation that can turn on those genes.

It is what they call the epigenetic effect, where these bad bacteria can change and modify the genes, the function of your genes, and cause them to function in a negative way. Some other ones, again, that include insulin resistance, fatty liver, gestational diabetes, high lipids, type 2 diabetes, irritable bowel, non-celiac gluten sensitivity, and environmental enteric dysfunction. You have so many nerve cells in your intestinal tract, and that is your enteric nervous system, and we are finding out more and more that they are so important. Small intestinal bacterial overgrowth can definitely cause diseases in the proximal intestinal tract. We see, as I mentioned, schizophrenia and autism. Also, brain and liver cancers.

Tweet: It’s what’s known as the epigenetic effect—where harmful bacteria can alter gene function, causing genes to behave in negative ways.

I did not know about the brain cancers, going over what we had just talked about in terms of the gut-brain access, and then the leaky brain barrier from the leaky gut. Makes sense, right? It’s because you are going to get more toxins that are going through to the brain, and all of that will cause inflammation. 

It makes sense. It is again, we are saying it is correct. We are seeing so many cases of colon cancer. In fact, there are more colon cancers now in people younger than 65 years old than there are in my age. 

They keep lowering the screening age because of that.

Gut Bacteria Causing And Exacerbating Eating Disorders

Something is doing it. The other one I was going to briefly mention is this gut bacteria causing eating disorders.

Which is interesting because that is a huge issue, especially for the teenage group, middle school, college, I think eating disorders, and then it can continue as they are adults too. I definitely want to get into that because I could see how that could then cause a cycle that gets worse. You start having an eating disorder, and then that gets your gut biome off, and then that could trigger. It is like a cycle because then another vicious cycle is off, and then you are more predisposed to getting the anxiety and getting. 

I thought this was fascinating when I first read it because it could be a potential treatment to help with those who are binge eaters or are struggling with anorexia, because they are labeled under psychiatric illness. They usually give them psychiatric meds. If they could just try doing this, at least to add it to their protocol.

They may better decrease some of the medicines that they require, something at least you know, I think anything that can help with that treatment, because it can be so hard to treat. Yeah, anything that can help is good.

In my day, they had a famous singer, this is just a little aside, but Karen Carpenter. She had a beautiful voice, and she actually died from anorexia nervosa. 

It is really difficult to treat. Some of your cases of anorexia are very difficult to treat, and it is really sad. I think that anything that can help is good.

This study showed that gut dysbiosis can definitely trigger binge eating and weight gain, also. There were similarities in microbiome patterns between humans and mice with compulsive eating disorders, including increased proteobacteria and decreased actinobacteria and Blautia. Now you do not have to remember the names, but it is just saying basically these good bacteria were lowered and the bad bacteria were higher in these binge eating patients. The gut-brain axis plays a crucial role in food addiction and binge eating disorders, and gut microbiota can produce substances affecting your appetite and mood, potentially influencing eating behaviors through the vagus nerve.

I thought that was interesting too. We will get into it, the GLP-1 agonists and how they work, and research has identified distinct neural pathways for fat and sugar cravings that originate in the gut. I am a chocoholic. When activated simultaneously, these pathways lead to this increased dopamine release. That is the chemical that is a pleasure chemical in the brain. That drives overeating. If that is off, then your appetite is going to be off. Akkermansia muciniphila, that is a very popular bacterium we are reading a lot about, but it is a beneficial gut bacterium, and here is where it goes with the GLP-1 medicines.

Akkermansia is associated with improved metabolic health and weight management. It enhances gut barrier function. Reduces inflammation and may help regulate your appetite through effects similar to these GLP-1 agonist meds like Ozempic and all the others. Muciniphila, remember, means mucin, and then philia always means, in the Greek, loving. It is mucin-loving. If this Akkermansia, this beneficial gut bacterium, is not fed with the healthy fibers that we were talking about in Inulin and so forth, and polyphenol-rich foods, eventually it will feed itself on your mucus lining.

You want to make sure you get the whole thing correct and proper nutrition for this bacteria, so then it can have the beneficial effects of reducing inflammation and potentially reducing weight gain and all of these other appetite regulation. There are a few more on these if you do not mind. I would like to mention this new kid on the block that I have read about, Turicibacter, and this was a study that was recently published in Cell Metabolism, where these investigators narrowed a long list of potentially anti-obesity microbes, and that would be very popular to get.

The one that came out as the top one that was beneficial was Turicibacter. In mice fed a high-fat diet supplement with this bacteria led to less weight gain, lower blood sugar, and lower levels of fat in the blood compared with controls. The team focused particularly on these ceramides. Now, what are ceramides? These are bioactive lipids that rise with high-fat diets, and they are increasingly implicated in causing metabolic dysfunction. A high-fat diet can release these ceramides. These elevated ceramides will increase intestinal fat absorption, promote fat storage, raise your sugar, and raise your insulin resistance.

They have also been linked, obviously, to type 2 diabetes and cardiovascular disease. Some studies suggest that ceramide levels can actually be a better risk a potentially risk factor to measure than LDL cholesterol, but anyway, here is where it comes in, this bacterium, the Turicibacter, produces its own lipids, and these are good lipids that it produces. Interestingly, this bacterium produces its own lipid molecules in the gut, but rather than worsening metabolic health, these lipids that this bacterium produces appear to suppress the ceramide production of the bad guy ceramide.

The ceramide surge is what is released when you have a very high-fat diet, and it has negative implications. Here, taking this, Turicibacter negates that effect because it produces its own lipid and lowers the ceramide. That is why they are seeing really good results in this bacteria interrupting that vicious metabolic feedback loop that you were talking about and pushing the patients, that vicious metabolic loop is what is leading to the obesity and sugar abnormalities.

If you take this little bacteria, it has been shown to really help with obesity and cause benefits for your metabolic health. It is a new kid on the block, and whether they can formulate this, I think the best way is going to be getting foods, and I did not have time to look up foods that are high in this particular bacteria, but I would bet it is a bacteria that is high in content in a Mediterranean diet.

It would make sense since the Mediterranean diet is so helpful for your cardiac health and just overall health.

Overall gut health, too, we will find out.

It is interesting, especially the cardiovascular effects, too.

It’s because we keep hearing things about Akkermansia, and that is so beneficial, and yes, it can be if it is properly nourished with fiber, but it is also hard to actually get that in you because it is an obligate anaerobe, which means it cannot have any oxygen exposure. Again, it is hard to get that concentration. Later on, I will go into some researchers are using a not using the live Akkermansia, but using some of the protein fragments of Akkermansia with some benefit. This one is I think, we are going to find out a lot more about it from that study.

That is so interesting. Let's get into a little bit about just the gut permeability and autoimmune issues. We talked about that before, right? People have genes that can predispose them to certain autoimmune issues, meaning the body is attacking itself. How does the gut play a role in that? Just like this gut dysbiosis, meaning that the gut microbiome is out of whack.

It is important to realize that after we went through COVID and the exposure to this spike protein and all the health issues with COVID, we do know it interrupted the integrity of the gut lining. We saw so much inflammation, and because it interrupted the integrity of the gut lining and caused leaky gut, we also saw a rise in these autoimmune diseases.

Tweet: It’s important to recognize that after COVID and exposure to the spike protein, we saw disruptions in gut lining integrity, increased inflammation, and a rise in leaky gut and autoimmune conditions.

I wonder if that also had an effect on what people call long COVID, too.

It has been a problem with long COVID. As far as we know, it compromised your gut integrity. We saw this surge in autoimmune diseases afterwards. We know that dysbiosis, gut permeability, and autoimmune diseases are related, and there is a part of our intestinal tract called the ileum.

Just for people to know you have your intestines right. You have your small intestines, which most people have heard of, and then you have your large intestine, also colon, but your small intestine actually has three parts to it, so it is the duodenum, jejunum, and the ileum. This is one of the three parts of the small intestine. 

Very good, thank you. The ileum is the most active section of our GI tract now, we are finding out, and the bacteria there contain a hundredfold more genes, this is what we discussed earlier, than humans, who have 20,000 genes. These bacteria in this particular part of our GI tract, the ileum, have more genes than we do. Infections or dietary changes can also affect the bacteria in that part of the gut, and then these epithelial cells secrete what they find out are glycosylated or sugar-coated proteins that form a mucous layer that serves as a barrier to other bacteria.

That is what helps with the tight junctions and prevents the bad bacteria from passing through, and protein fragments, all those other things we discussed. Microbes are necessary for digestion and metabolism, and our immune system. When we get into a proper balance, it can cause food intolerance, allergies, and autoimmune diseases. With inflammation and bad bacteria overgrowth, these epithelial cells produce, again, that protein zonulin that measures your leakage across it.

This zonulin is then secreted into the lumen, and it messes up the rate through receptor sites, it messes up that tight junction. It starts to break down. Now I was just studying this too. They have this new investigational peptide called larazotide. It actually has been in the studies antagonizes this zonulin, this bad chemical that measures your protein, your leakage, your leaky gut.

This larazotide is just an investigational peptide at this point, but it blocks the effects of information that breaks down your gut lining. I guess the best way to do it is to have a healthy diet, but I am just saying that it is being used for celiac and some of these other diseases, autoimmune diseases. We do know patients with autoimmune diseases have autoantibodies, right? 

Basically, their body is attacking itself.

It does not recognize itself as a normal part of its tissue and attacks it, and that leads again to things like rheumatoid arthritis, lupus, and they actually are found to have higher zonulin levels. That shows that they have a higher amount of leaky gut and fewer tight junctions. We see these other markers they have out here for leaky gut, but that zonulin is a big one. Is LPS, the lipopolysaccharide toxin, released from bad bacteria? It would be interesting to see if it pans out, but I thought that it was interesting they are working on developing these medicines that will counter these problems. Again, you do not want to just get a pharmaceutical to counter that. You want to find out the root cause and correct the root cause right.

Honestly, it is not exciting, but most of the time it is something very boring, like eating more fiber eat a healthy diet. 

Eat real food, not processed food.

A lot of times, people say they want to have the root cause, but in reality, we are still having sodas or junk food.

The ultra process. 

It is like, at the end of the day, it is this very boring, very basic, eat healthy, limit the processed foods, up the fiber, add in these prebiotic foods, these probiotic foods. It is the boring basics, but they are very important.

If you get the good bacteria repopulated at a good concentration, then you see all these factors will be corrected, these healthy consequences of an unhealthy gut, and you do not need even GLP-1 agonists. Your body will naturally produce it, as we just read with Akkermansia and a good, healthy microbiome there. I agree. We are in a time where people do not want to give up ultra-processed foods and foods that they really enjoy.

I do not want to downplay the addictiveness of it either. We talked about that response to dopamine. That dopamine response is like, it is the addiction response. It is that pleasure reward, you know? It is the same as when people are gambling, when people are going shopping, or for addicts. You are getting that dopamine response for drug addicts. Food now, the way it has been engineered, is to bypass the body's like checks and balances. It is to stimulate more of that dopamine because then they know we are going to buy more. This ultra-processed food is really so dangerous because it makes it so difficult for people to actually have that healthy response. I do not want to downplay the addictiveness of this ultra-processed food. 

For me, with chocolate and sugar, that is really something we should get rid of in our diet for sure. I can totally relate to people who have that difficulty.

I also think that is where sometimes these GLP ones can help, because a lot of times people are in this vicious feedback loop where they have all these high addictions to food that they do not realize. It is causing this gut dysbiosis, which then is just this vicious cycle. Sometimes, we have these tools, and they can be healthy. I do not want to downplay that, but overall, it really is a lot of this.

While you are taking it, it would not hurt to start this change.

Parkinson's Disease Link To Gut Bacteria And Environmental Toxins

That is definitely what you need to do. It is a combination. It is not just taking a medicine, but also treating the cause and changing. You have something that is helping you. Something else that I think is so interesting is you know how gut dysbiosis is, this gut system getting out of whack. How can it affect Parkinson's? I have seen that a lot more in certain studies and articles about how this can actually relate to Parkinson's. I thought that would be interesting to go into.

Let's do that. I agree, because you are reading so much about that, the link between our gut and our brain, and especially the role it plays in the onset of Parkinson's disease. We see this was a recent article that added further evidence to this link because what they did was they identified gut bacteria likely to be involved and linked them to having decreased riboflavin, which is vitamin B2, and biotin, vitamin B7. These gut microbes that were bad were causing decreased production of these B vitamins.

The authors were hoping this would lead to a discovery that there would be a simple treatment that could at least help, which would be with the Parkinson's disease we are talking about, which would be these B vitamins. The supplementation theory targeted these two particular B vitamins, riboflavin and biotin. It holds promise as a potential therapeutic avenue for alleviating at least some of the Parkinson's symptoms and slowing down the disease progression. That was done by a researcher, Nishiwaki, in Japan. That study was published in May of 2024. 

For anybody who knows somebody with Parkinson's or has Parkinson's, unfortunately, while there is more treatment, there still is not a cure right now, and progress differently and so if there is anything like this, especially that is relatively low risk, taking a B vitamin, it is if there is some help that is great.

We will go into correcting your gut biome, which produces these B vitamins too. Anyway, the neurodegenerative disease impacts around this Parkinson's impacts around ten million people globally. I did not realize there are that many, and the symptoms usually begin with the first symptom, which surprisingly was constipation, and then sleep problems, and that can occur up to twenty years before someone develops Parkinson's disease.

Previous research found people with Parkinson's disease also experienced changes in their microbiome long before this debilitating muscle control, and all these other symptoms occur with Parkinson's. While different groups of bacteria were involved in different countries, because they examined the flora from China, Taiwan, Germany, the US, a few of these countries, they all influence, enough, these pathways that synthesize B vitamins in the body, in your gut, these good bacteria that make those B vitamins for brain health.

Tweet: Previous research has found that people with Parkinson’s disease showed changes in their microbiome long before the onset of motor symptoms and other debilitating effects.

The team also found that changes in gut bacteria communities were associated with a decrease in riboflavin and biotin in people with Parkinson's disease. It showed that the lack of these B vitamins was then linked to a decrease in our short-chain fatty acids. Certain polyamines, molecules that also create this healthy mucus lining for our gut integrity. Deficiencies in these small chain fatty acids would indeed lead to thinning of this mucus layer or gut lining and increase the leaky gut. That was also seen, the thickness of that gut lining and the leakability. I do not know if that is a real word, but they were both observed in patients. Almost all the Parkinson's patients had that. 

Correct me if I am wrong, but this is what we were talking about earlier in terms of you having the highly fermented foods, the probiotics that end up then making these short-chain fatty acids like the butyrate and things like that.

They are food to allow your good bacteria to populate, which then produce these B vitamins. We know that they produce the small chain fatty acids. It is really feeding the good bacteria so they can produce the good products, which include small-chain fatty acids and these B vitamins. They suspect that the weakened protective layer exposes this intestinal nervous system called the enteric nervous system in our intestinal system to actually leaves them exposed to more of the toxins that we now encounter in our daily life, which includes the GMO and non-GMO even, wheat products, glyphosate, microplastics, and we are going to go into a whole thing. One of the ones I want to mention is that we already know there is confirmation, pesticides and herbicides, cleaning chemicals, they have all been implicated in triggering Parkinson's disease. Last episode, we mentioned that on golf courses.

Environmental Toxin Exposure From Pesticides And Mitigation Through Air/Water Filters

Which is like, we are in Florida. Golf courses are all over. It used to be, and it still is, very popular for people to live next to a golf course, which used to be like the prime spot to live. We will go into this a little bit, but it is scary. 

Now that they have started cleaning it up. 

Even if you are not right next door to a golf course, there are so many around here. All of the spraying that they do is still going to drift into the air and everything. Anyway, so I guess yeah, let's talk a little bit about the golf courses and the possible Parkinson's link that has been.

You could just see the increase from all the toxins that we are living with now, but pesticides sprayed on these golf courses are found to be aerosolized to and they can frequently drift in the air. The closer they found out, the closer you live to a golf course, especially within a mile, the greater your likelihood of developing Parkinson's disease. Specifically, your odds nearly double, a whopping 126%, when you reside less than a mile from these chemically maintained spaces.

Even they suggested when, try to find out if you are living on a golf course and you cannot move, you should try to know when they are spraying and close your windows. You need to know which way the wind is blowing so you can limit your exposure to the aerosolized chemicals. Even modest increases in distance can cause exposure, even up to three miles away.

If you move further out, the risk of Parkinson's from move further out from these golf courses that are spraying with these pesticides, the risk of Parkinson's dropped more notably at about a thirteen percent drop for every extra mile. However, the highest risk zone consistently hovered at the shortest distances, which again highlights the finding that proximity matters the most in determining whether you are going to develop Parkinson's from golf courses.

It makes sense, right, because you are just at the higher levels of exposure.

Drinking water near golf courses also heightened the risk. Residents dependent on groundwater within these contaminated zones also experience nearly double the risk of developing Parkinson's. The research strongly believes that pesticide residue infiltrates the local water supplies, not just aerosolized in the water supplies, and then becomes a direct threat to residents who consume this water daily, unaware of this invisible chemical burden they face, especially if they do not have purifiers like reverse osmosis.

It makes sense, right, because they are spraying the grass, they are trying to keep the area without the weeds and have it nice looking nice so that everything else does not pop up, but that is then getting into the ground, then goes into the water, which then people drink. It makes sense that it goes air and water, but that is where I think a lot of times people do not talk about how important a good air filter system is.

That is a point. 

A lot of times, people just talk about whether you have asthma or COPD or like a respiratory issue, but I think as we are learning about all of these exposures, there are a lot of people who might say, “I live on a golf course, but I cannot sell my house right now and move.” This is where, at least getting a really good air filter system in your house in your rooms, where you are at least trying to clean that air as much as you can, and a good water filter system. Cleaning out these toxins.

If you have to get a new car with all the forever chemicals in it, keep the windows rolled down, especially on a hot day, but we go into that on episode two.

For those who are like, “I live on a golf course, this is horrible.” There are things you can do to mitigate the negative. That is where I think an air filter and a water filter really are, can be very helpful.

The other one I wanted to mention is Atrazine. This is another herbicide in agriculture, and it quickly spreads through water systems and air, exposing people also through the drinking water, food consumption, and environmental contact. This recent research also shows that Atrazine exposes and accelerates our brain aging and increases the risk of neurodegenerative diseases like Parkinson's. There is always something else out there. Such toxins, we know from Parkinson's patients, it has been shown to cause overproduction of the alpha-synuclein molecules.

These are the molecules that attack the dopamine-producing cells in your brain in a part of your brain called the substantia nigra. That is how it works for Parkinson's. It causes the production of these horrible alpha-synuclein fibrils, tangles, and molecules that then inflame the nervous system and eventually lead to these debilitating motor and dementia symptoms of Parkinson's. All those pesticides and herbicides are just not good. It is also possible.

We are hoping at least that taking from that Japanese study, taking some high doses of Methylated I would say methylated B vitamins, because that goes through the blood-brain barrier easier, the methylated form of B vitamins can prevent some of the damage. It all suggests the importance of a healthy gut microbiome to protect and reduce the negative effects of these toxic pollutants in our environment. We are always finding out what you eat and how healthy your gut is.

Tweet: The importance of a healthy gut microbiome lies in its ability to protect against and reduce the harmful effects of toxic environmental pollutants.

It has such importance on our aging sleep quality and our overall health. We are finding out more and more that this is just so important for our overall health, and we will go into it in the other podcast. There is research has also found that some bacteria in our guts can absorb and store the forever chemicals, the polyfluoroalkyl substances, and those are called our forever chemicals. There is so much ongoing research on this topic.

High Fiber Diet Decreasing Absorption Of Forever Chemicals And Microplastics

There is, which, and I do think it is interesting with the microplastics and the forever chemicals now it is coming out, and when you have a high fiber diet, it almost coats the intestine. That helps decrease the absorption of these microplastics and forever chemicals, which is yet another reason to have a healthy diet and a high fiber diet. It is again reconfirming how important this is.

Oats and some other grains were very important for what you were just describing. cannot remember the chemical.

It helps with the mucin layer. It helps with that increased fiber. 

Anyway, this is interesting because this would come out of Cambridge that they theorized that boosting the good bacteria could actually help if you get this particular bacteria, reduce the polyfluoroalkyl substances of forever chemicals. We could actually excrete it. Again, that is pretty new. 

That is a lot. It's just like the tip of the iceberg in terms of all the effects that gut health plays. We are going to continue more of this on a few more episodes, all about gut health. Thanks so much. This was great. I am sure everyone learned a lot from this first part of our series, and we will continue soon. 

Sounds good.

Thanks.

Bye.

Important Links

• Dr. Karen McCarthy on LinkedIn
  
  

About Dr. Karen McCarthy

Dr. Karen McCarthy is a highly respected internal medicine physician known for delivering detailed, prevention-focused care and for taking the time to truly understand each patient’s overall health. In addition to a distinguished medical career, Dr. McCarthy founded the City Rescue Mission medical clinic more than 30 years ago and has spent decades caring for underserved communities. 

Through numerous medical mission trips and a lifelong dedication to service, Dr. McCarthy has made a lasting impact both at home and abroad.  She takes an in-depth approach to health, looking beyond immediate symptoms to better understand root causes and support long-term wellness.

Gut Health Podcast References:

• The Microbiome and Cancer.
  The Journal of the American Medical Association. 2025. Fernandez E, Wargo JA, Helmink BA.
• Exploration of Gut Microbiome and Inflammation: A Review on Key Signalling Pathways.
  Cellular Signalling. 2024. Nigam M, Devi K, Coutinho HDM, Mishra AP.
• The Relationship Between Gut Microbiota and Inflammatory Diseases: The Role of Macrophages.
  Frontiers in Microbiology. 2020. Wang J, Chen WD, Wang YD.
• The Gut Microbiota and Inflammation: An Overview.
  International Journal of Environmental Research and Public Health. 2020.
  Al Bander Z, Nitert MD, Mousa A, Naderpoor N.
• Gut Microbiome and Immune System Crosstalk in Chronic Inflammatory Diseases: A Narrative Review of Mechanisms and Therapeutic Opportunities.
  Microorganisms. 2025. Feng JJ, Maddirala NR, Saint Fleur A, et al.
• Microbial Dysbiosis in the Gut Drives Systemic Autoimmune Diseases.
  Frontiers in Immunology. 2022. Mousa WK, Chehadeh F, Husband S.
• The Human Intestinal Microbiome in Health and Disease.
  The New England Journal of Medicine. 2016. Lynch SV, Pedersen O.

Topic: Gut microbiome in human health and disease

Scope: Development, dysbiosis, mechanisms, and therapies

Summary

Narrative review of the human intestinal microbiome describes how gut

microbes change across the lifespan, what shapes them, and how altered

microbial communities are linked to many diseases. The review highlights

a few clinically relevant examples, especially fecal microbiota

transplantation for recurrent Clostridium difficile infection, but emphasizes

that most microbiome evidence is still correlative or preclinical and not yet

ready to establish cause-and-effect for routine care.

Research in Context

• 2016 NEJM review: foundational synthesis of then-emerging

evidence on intestinal microbiome roles in health/disease

• Subsequent literature: strong validation and extension; shift from

association studies toward mechanistic precision (species/

metabolites/pathways) alongside exponential publication growth

• Clinical translation: accelerated to FDA-approved fecal microbiota

transplant products for recurrent C difficile by 2023; expanding

microbiome therapeutics and efforts to address interindividual

variability/standardization

• Short-Chain Fatty Acids: Linking Diet, the Microbiome and Immunity.

Nature Reviews. Immunology. 2024. Mann ER, Lam YK, Uhlig HH.

• Dietary Fiber and SCFAs in the Regulation of Mucosal Immunity.

The Journal of Allergy and Clinical Immunology. 2023. Tan JK, Macia L, Mackay CR