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Discover the exciting latest breakthroughs in brain science that can unlock your full potential. This engaging journey is packed with clear explanations and practical, actionable tips that can truly transform your life for better.
Dr. Marc Milstein: [00:00:02] Have you ever heard the saying, 'trust your gut' or 'listen to your gut'? There's actually some real science there. What's happening in your gut can impact your memory, your brain health, aspects of mental health, also immunity. It's one of the most fascinating areas in brain health today, in overall health. Hi, my name is Dr. Marc Milstein, and welcome to Best of Your Brain podcast. I'm very excited to talk to you today about the gut-brain connection. One of my favorite areas of research, and what we're going to focus on, is how does this work, and also what are the things that we can do to really optimize our gut health to improve our brain health. Now, this is an area that is filled with marketing and hype. So we're going to focus on what is scientifically accurate. What are the little things that have a big impact? Now, you might have heard that the gut is referred to as the second brain, and there's actually brain cells and neurotransmitters in the gut. But we're going to focus on for a moment is a little bit about how our brain works, so we can understand that connection. What we're going to focus on for a couple of moments is some aspects of our brain health. Now your brain is about 3 pounds, and we could think of it almost like a factory. It makes products. It makes connections, every time you learn something new, when you make new memories.
Dr. Marc Milstein: [00:01:18] But your brain also makes byproducts, waste, trash, toxins; these are like leftover chemical reactions, broken-down proteins, just part of all the hard work your brain is doing. And in a year, your 3-pound brain makes 5 pounds of waste in trash. And as you can imagine, you have to get rid of it. Otherwise, this waste and trash can interfere with not just how you feel, your mood, your memory, but also productivity and long-term brain health. And as we get just a little bit older, our brain's ability to remove this waste and trash can become less efficient and effective. So what we're going to focus on is how do we clean our brain? And what we understand now is one of the most powerful things we can do to clean our brain, remove this waste and trash, is really take care of our gut. So the connection to all of this is that you have this amazing human cell swimming around your brain right now, eating up the trash and the garbage for you. It's called a microglia. And imagine like a fish tank. You know, you look in the aquarium and you see the bottom feeder swimming around. Well, you have something just like this in your brain. Eating up the trash, keeping your brain clean and protected, removing this waste. But these microglia can get confused. And instead of eating up the trash in the garbage, what do you think they start to eat? The good stuff.
Dr. Marc Milstein: [00:02:34] Healthy brain cells. And that's when we can see devastation to memory. That's when we can see an increased risk for anxiety, depression, also Alzheimer's, dementia. So really, what we're going to focus on is how do we keep these microglia focused so they're just doing their job. Just eat the trash in the garbage. Don't get confused. And the way the microglia get confused in part is based upon what's happening in the gut. And the connection here is inflammation. Now, inflammation can start in the gut, and it can seep into the bloodstream, travel to the brain, and trick those microglia into going into attack mode. So really what we want to focus on is how do we keep inflammation low in the gut? And one of the connecting points here is we actually need to talk about bacteria. Good bacteria and bad bacteria. And my goal for this podcast is for you to have the most exciting podcast you've ever heard on bacteria. Now, I know that's not a very high bar, but I hope you leave this podcast as excited as I am about bacteria, or maybe even close to as excited as I am. So to put this all in perspective and to really talk about this connection, and how is bacteria playing a role in our brain health and keeping our brain clean, let's take one step back.
Dr. Marc Milstein: [00:03:51] Let's think about the human body head to toe. How many human cells, lung cells, liver cells, heart cells, brain cells: how many human cells do we have? Well, we have about 38 trillion, give or take a trillion. And whenever I bring that up, people always ask me, who counted? Who counted? Well, if you were to count one, two, three, four, all the way to 38 trillion, we'd be here for a million years. So nobody counted. They actually extrapolate, take little amounts, and then do the math. But if you're 38 trillion human cells, how many bacteria cells are living on top of you and inside of you, mostly in your gut? Well, there's about 37, 38 trillion bacteria cells living on top of you and in your gut. So I hate to break it to you, but you are pretty much half human, half bacteria. And what we realize is that this bacteria is playing a key role in our brain health, also in multiple aspects of our health. But you might be stuck on that point, wait, I'm half human, half bacteria? Does that mean that half my body weight is bacteria? Well, if you were to take all the bacteria out of your body on top of you and inside of you and kind of lay it next to you on the table, and I know that's kind of gross to think about, it would be about 5 pounds. And I know that might not make sense, but bacteria is really teeny tiny, much smaller than a human cell.
Dr. Marc Milstein: [00:05:11] So even though the total weight is significantly smaller, the number of bacteria and the number of human cells, bacteria cells and human cells, is about equal. So let's go back to this question. What's it all doing? What's the point? Well, we used to think that this bacteria was like passive riders, like along for the ride. But now we understand that they play a key role, and it's almost like we have this agreement with our bacteria, especially in our gut, where we provide this bacteria a really nice place to live, it's a really good environment, mild winters, perfect humidity. They like it down there. And in exchange for this really nice place to live, they do work for us. So when you eat food, a lot of it you can't digest on your own. It gets down into your gut, the food, and your bacteria digests it, pretty much eats it for you, and extracts nutrients that then pass through your intestinal wall and get into your bloodstream so you can actually get the benefit of your food. Bacteria also make vitamins for you, but bacteria also are like almost like a bouncer at the front door of a nightclub. And the bouncer decides who's going to get in the club. Well, essentially, bacteria lines the wall of your intestine and determines what's going to pass through. And there's good bacteria that will do a really good job and not let toxins or dangerous substances get into your bloodstream, which can do significant damage.
Dr. Marc Milstein: [00:06:33] But then there's bad bacteria. The bad bacteria actually don't do a very good job. And they let dangerous things get into our bloodstream, which can upregulate or mess up our immune system or just do damage to our body. So essentially, what we're going to be talking about is how do we have more good bacteria and less bad bacteria? But before we get there, I do just want to ask you this question Does Tylenol work on you? Is it something that provides you pain relief, or is it almost like taking a Tic Tac? Well, when a Tylenol is actually effective, those individuals often have certain types of bacteria species living in their gut that are able to break down that medication in a way that it passes through the bloodstream. People that don't get the benefit of Tylenol, often they don't have those types of bacteria. So what we realize is also that our ability to use medication effectively can be determined based upon our gut bacteria. We even see that certain cancer drugs and cancer treatments work better in individuals with certain types of gut bacteria. And the goal of all of this is that can we pair the right medication to the right individual based upon their gut bacteria, but also can we optimize individual's gut bacteria so that they get more of the benefit from certain medications and treatments? There's a lot of hope here that we can really optimize the treatments for people.
Dr. Marc Milstein: [00:07:55] Now let's take this one step further and let's talk about this gut-brain connection. Really fascinating area that are we, are things happening in our gut that impact our thoughts and our feelings and our mood? And an experiment that really surprised people in this field was they looked at mice, and mice have different personalities. That's just something we have to accept as part of the experiment. There are some mice that have very adventurous, outgoing personalities. They're very daring. And there are some mice that have very shy like wallflower personalities. And so the scientists said, well, what if we take the gut bacteria from the adventurous mouse and we transplant it and put it into the shy mouse? And then we take the gut bacteria from shy mice, and we put it into the gut of the adventurous mouse, what would happen? Well, it turns out that their personalities switched, the adventurous mouse became more shy, and the shy mouse became more adventurous. And that seemed so strange, so bizarre. But we actually see this in humans as well. We understand that humans that are suffering from things like anxiety or depression, they often have different types or species of gut bacteria that we can tie to their mental health. And so how does this all possibly work? Well, good bacteria can release factors or chemicals that seep into the bloodstream, make their way to the brain, and can impact aspects of how our brain is functioning.
Dr. Marc Milstein: [00:09:21] Bad bacteria can release factors that have an opposite effect, can have a negative impact on our mood or mental health. We can even take this a step further, and we understand that there's a connection, a direct connection between our brain and our gut. There's something called the vagus nerve, and I like to think of it almost like a guitar string. And imagine if you took this guitar string and you essentially plucked it or played it very rapidly, that could cause a lot of stimulation or a lot of signals that would go to the brain. We understand now that certain types of bacteria, more good bacteria, they can send signals that stimulate that vagus nerve in a way that send calming signals to the brain, whereas bad bacteria will send signals that will stimulate that vagus nerve in ways that will send signals that can have negative impacts on brain health. We even see recent studies that show that the types of bacteria that are living in our gut can have an impact on how resilient we are to stress. One way to think about this is that this connection between the gut and the brain can be like a two-way street. And in the past, if somebody, for example, had IBS or irritable bowel syndrome, we would think that they were anxious, they were feeling anxiety over their health condition.
Dr. Marc Milstein: [00:10:29] And we would often see that, that people with IBS have higher levels of anxiety. They must be worried about their health. But we now understand that in some cases, what's actually happening is the IBS is causing bad bacteria to grow, and that bacteria is sending signals to the brain, which is causing that person to have a higher risk for anxiety or having anxiety symptoms. So we actually look at this as an opportunity to say that this two-way street gives us avenues that we can provide more treatments to people. If somebody is suffering from IBS, or we want to think about how to optimize their brain health or their mental health, or their stress management. If somebody is having issues with their gut health, we want to think about their brain. If somebody is having issues with their brain health, we want to think about how do we optimize the gut. What we look at is an opportunity to say that if somebody is having issues with their gut health, what can we do to optimize their brain health to improve their gut health? And if somebody is having issues with their brain health, what can we do to optimize their gut health to improve their brain health? So it gives us hope that there's more strategies and empowerment to treat people and give them the best possible treatments.
Dr. Marc Milstein: [00:11:34] We've been talking about some of the most complex things in the universe: the human brain, the microbiome, which is all the bacteria growing in one's gut, and also we're going to add on top a new layer of complexity, the immune system. We're going to do all of this in this 15-minute podcast and get some take-home tips. So let's talk about the immune system because that's the final piece that really ties this all together. So in the past, we thought about the immune system as this system that was really designed to just protect you, keep you, and get rid of things that aren't you. Any dangerous bacteria, viruses, anything that's not you get rid of. But how do we now think about this when half of you isn't you, half of you is bacteria. So how does this possibly all work? How does the immune system know what to do? If you ever watched a show like Law and Order or The Blacklist, like these kind of cop procedural detective shows, we understand that there's kind of a formula in these shows where the detective or the cop will be looking for the criminal, and in order to solve the case, they will go talk to another criminal. Someone who's like in a back alley, usually, in the episode of the show, or somebody that has ties to the criminal world, and they'll ask that person questions and they'll get information.
Dr. Marc Milstein: [00:12:48] It's like an informant. Well, we realized that the relationship between bacteria and our immune system is very similar. There are bacteria that are like informants. They actually tell the immune system, that's good bacteria over there, you want to keep them. They're doing a good job. They're like the bouncer in the club. They're making vitamins and key nutrients. Don't destroy those. But those are the bad bacteria in this other part of the body. And you want to get rid of them. They're not doing a good job. They're dangerous. And what we realize is that good bacteria give the immune system good information. Bad bacteria give the immune system confusing or bad information, and they tell them to do the wrong things. In some cases, tell the immune system to attack our gut or our joints or our heart, causing inflammation. What we call often autoimmune conditions can be tied to bad bacteria sending bad information. So essentially how we put this all together is we just really want more good bacteria, less bad bacteria, so that the good bacteria can do their job and tell the immune system what to do. So what are the take-home tips? We talked about a lot. So how do we break this down? Well, essentially, we want to feed the good bacteria, starve the bad bacteria. So how do we starve the bad bacteria? Well, we don't want to feed them.
Dr. Marc Milstein: [00:14:03] So what do they eat? Well, I can pretty much sum it up. I was in a museum in Chicago. The science museum there, if you've been there, it's a great museum. And they have this Twinkie. They unwrapped it about 17 years ago. It's sitting there unwrapped. Looks good. Looks like you could, looks like you could eat it today, and it would just taste fine. Probably taste pretty good. That's what we're worried about. These foods that never spoil. It's the additives, the preservatives, the ultra-processed ingredients, they feed bad bacteria. And that can cause inflammation to spread through our bloodstream, make its way to the brain, and trick those microglia we were talking about in the beginning to attack healthy brain cells. Or just confuse the immune system into attacking parts of our body. So a simple tip: next time you're eating something, if it's in a package, look at the packaging. If you're like, I can't pronounce any of these ingredients, this looks like a chemistry experiment gone wrong. Those are the things we want to minimize. We want to be able to pronounce the ingredients. Whole natural foods most of the time. Now if we say, okay, well, how do we feed good bacteria? What do we do? Well, this is where the field of prebiotics comes in. And prebiotics are basically the foods that the good bacteria like to eat. And it turns out they love to eat fiber.
Dr. Marc Milstein: [00:15:19] There's a saying in this field that if fiber was a drug, people would be lined up around the block to get it. And what happens is that the good bacteria, they love to eat fiber, and they actually release this chemical compound into our gut called butyrate. It's actually an anti-inflammatory. So really what we want to be doing is just trying to get about 25 to 35g of fiber a day. And we see evidence now that when people get about 25 to 35g of fiber a day, they lessen the inflammation in their gut. We're actually also seeing evidence that someone gets that amount of fiber in their day, they get better deep sleep that night, which is another way to clean your brain. Get a good brainwash. We talked about that in another episode about sleep. But the question becomes what percentage of our population is getting 25 to 35g of fiber a day? Less than 5%. So we're just saying this is an opportunity to just add some things to our plate. We don't have to take anything away. We can just add some things. Nuts, grains, seeds, and avocado. If you like guacamole has half the amount of fiber that you need in a day, and you can eat really healthy and still not get to that number, that 25 to 35g. So a quick tip is take Google or ChatGPT and just enter in what you're eating for breakfast, lunch, and dinner.
Dr. Marc Milstein: [00:16:32] Write it down, put it, put it in there, and just see, you know, ask how much fiber is in what I'm getting breakfast, lunch, dinner, and some snacks. And if you're not getting it, just add some things. A small addition of fiber to get to that number can really have a positive impact on our overall health. The food industry can be very tricky, so we just want to be aware of some of their tricks, some of their labeling tricks. If they say 100% whole grain or 100% whole wheat, that very likely has some good fiber in it. We want to look for things like oats, flax, rye, barley. Those are all things that have good fiber, but also looking at the numbers. But they can also label foods and say things like wheat or made with whole grains. And that doesn't necessarily mean there's really much fiber at all. So just taking that extra step and turning over the packaging and checking that number and making sure we're getting in that range. Now, it's very important to mention that diet is very individualized. Some of the foods that we're talking about are right for some people. And some of these foods are wrong for some people. They're not right for everybody. So even just taking that step and working with your doctor or nutritionist and finding the right combinations for that individual can be really helpful, really helpful for our overall health.
Dr. Marc Milstein: [00:17:40] Now last point, do you like chocolate? Do you crave chocolate? Do you love chocolate or are you a chocoholic, or is chocolate like no big deal to you? Well, if you love chocolate, who really loves the chocolate? If you said bacteria, if you pretty much say bacteria at any point today, you get the right answer. But if you say bacteria, you're right. We actually understand now that there's bacteria living in our gut, and they actually send signals, they release chemicals into our bloodstream, and send signals via the vagus nerve to our brain, and send signals to our taste buds to say, go get me some chocolate, I want chocolate. So when you're craving certain foods, what we realize it's the bacteria that's often craving it. And it's sending signals to our brain to tell us to get it. Really interesting to think about. Now in all this complexity that we talked about, what's really nice is that some small, simple things can go a really long way. Amongst all the noise and hype and marketing that we're hearing about, just choosing or making some choices when we're eating can really protect our brain, protect our gut, help our immune system. So I hope you leave here today as excited about bacteria as I am, or at least almost as excited. And I hope you and your bacteria have a great next meal. Thanks for listening. Thanks for watching.