Many of our favorite products are built via an assembly line, which is all about production and efficiency. Each person has a role in the assembly line, and then passes off their task to the next person. Everyone is working towards the same goal, but they don't have much overlap beyond that.  For years, this is how scientists thought of our gut and digestive system. It was seen as a series of parts that helped achieve a collective mission, not something intricately interconnected. And certainly not something that impacts the way we feel, sleep and think. In his groundbreaking work, The Mind-Gut Connection, Dr. Emeran Mayer argues that this is an outdated view of the digestive system. For years, scientists compared our digestive system to a pre-programmed machine: "We ate, chewed, and swallowed our food, then our stomach broke it down with mechanical grinding forces assisted by concentrated hydrochloric acid before dumping the homogenized food paste into the small intestine…which disposed of what remained by excreting it," Mayer says of their views.  Eat, process, excrete, repeat.  This was an easily grasped concept, but it was too simple. Instead, we should be looking at our gut more like a supercomputer. In this "supercomputer" model, we see that everything is connected and way more complex and intricate than previously thought.  As Chris Stapleton once mused:  "I drink because I'm lonesome, and I'm lonesome 'cause I drink." Both mutually affect the other, and you can't solely point to one as the root cause.  The two-way connection from our gut to our brain works similarly.  Uncovering more about the gut microbiome (which we'll get to in a minute) has led to breakthrough discoveries in just how much something like anxiety, for instance, is tied to gut health. We already knew that our bodies were incredibly complex, filled with myriad functions that we don't even consciously think about on a daily basis.  However, the stakes are high if the tiny collection of microbes inside of us (our gut microbiome) can influence our susceptibility or resistance to disease, our emotional states, and the way our bodies process food.  Nutritional psychologists and researchers have been making ground-breaking discoveries that have shifted the ways we view food and diet's relationship with the mind and body – and these discoveries are relatively new.  That may lead to some natural skepticism, but with the studies we will unpack today, much of the research suggests or points to certain conclusions about the mind-gut connection. And while nothing is completely definitive, there's overwhelming evidence to affirm what we already know to be true: what you eat affects you in profound ways. However, there are so many factors beyond just the way we eat on a daily basis. Fascinating new research has shown factors like where you're born, how you're born, what you're fed as an infant, how your mother handled stress while you were in utero, how you handle stress, and beyond, can each uniquely impact our gut.  There's a lot of information to digest, pun intended, but the goal is simple:  To grasp a better understanding of how our internal supercomputer functions so we can leverage this to make better choices that improve our health on a daily basis.


The "microbiome" sounds like something weird you'd study in biology class, or the home of an alien species in a sci-fi movie. E.T…come…home. But in actuality, it exists right inside of us. Think of it like a city with trillions of residents scrambling around to do a different job. Here's how the Harvard describes it: "[It consists of] trillions of microorganisms (also called microbiota or microbes) of thousands of different species. These include not only bacteria but fungi, parasites, and viruses. In a healthy person, these “bugs” coexist peacefully, with the largest numbers found in the small and large intestines but also throughout the body." Yes, packed within your gut is a population of microorganisms a thousand times the size of earth's population. Not every one of these microorganisms is beneficial, but most of the time they live in a balance. When they don't, it leads to dysbiosis, which is an imbalance that occurs when unhelpful microbes overpower those that are more beneficial. "If there is a disturbance in that balance—brought on by infectious illnesses, certain diets, or the prolonged use of antibiotics or other bacteria-destroying medications—[imbalance] occurs, stopping these normal interactions. As a result, the body may become more susceptible to disease," the Harvard study continued.  In a feature by The Guardian, microbiome scientist James Kinross says that "the gut microbiome is the most important scientific discovery for human healthcare in recent decades. We discovered it – or rediscovered it – in the age of genetic sequencing less than 15 years ago." Later on in this piece, we'll focus on how certain diets perpetuate imbalance. But first, what do these microbes do inside our gut?

Role Of The Gut Microbiome

Primarily, they play a vital role in the function of our immune systems, digestion & absorption of nutrients, break down of toxins, and helps produce certain vitamins and amino acids. Research is also showing that specific intestinal microbes can drive the development of certain cancers, help prevent them, and also influence the efficacy of cancer therapies.  However, for the purposes of this blog, we're going to focus on a growing body of evidence that is showing that certain bacteria and the byproducts they produce, affect mood, cognition, and behavior.


Picture this. You spend months applying for that dream job, anxiously refreshing your email everyday and cranking your iPhone ringer up for any sign of news. After waiting extensively, your phone rings. "Hi, we're excited to offer you the position..."  Your heart starts beating faster and a smile begins to creep across your face. You try to contain the mounting joy as you compose yourself to finish the call. Immediately upon hanging up, you let out a borderline scream. YESSSSSSS.  One second of communication transmitted a massive amount of information, and in turn had a reciprocal effect on your body, emotions, and mood. Yes, our brain and gut is in constant communication, just as we are on that text thread.  "Not only do the gut and the brain communicate through the nervous system, but also through hormones, and the immune system," says Cleveland Clinic.  It's important to note that this communication is more like a high-speed fiber optic cable than a slow landline. And it's exclusive to the gut and brain.  "The brain is tied to the gut like no other organ, with far more extensive, hardwired connections," says Dr. Mayer. Fascinating. Our gut wasn't intended solely for digestion purposes, but rather complex intercommunication in our bodies.  What are some of the effects of this constant communication?  "Recent studies suggest that in close interactions with its resident microbes, the gut can influence our basic emotions, our pain sensitivity, and our social interactions, and even guide many of our decisions – and not just those about our food preferences and meal sizes," Dr. Mayer also added.  This might be head-scratching at first, as it may sound like your gut microbiome is "controlling" you or robbing your autonomy. As mentioned earlier, we have the equivalent of brain cells in our large intestines, but that doesn't mean that they have the same cognitive function.  Think of it like the Instagram algorithm. It certainly influences you, but it doesn't force you to watch or partake in the content.  Plus, the prefrontal cortex serves as a sort of human "override," according to Dr. Mayer. Even if brain circuits have been altered, the prefrontal cortex can help us learn new behaviors.  In other words, we aren't helpless. Keeping that in mind, what are some of the ways that our gut can influence our emotions, and vice-versa? Interestingly, we know more about how negative emotions affect our gut more than we know about the effect of positive emotions.  Going off that same hypothetical story, let's say you accept the dream job. However, things don't pan out as you expect, and after a few months, you're let go. You start fuming and feel completely stressed.  In response, your brain sends communicative signals to your digestive system, and your stomach begins contracting and ramping up acid production. This slows the digestion of whatever you had for lunch, as your intestines barely move when you're depressed.  "We now know that your gut mirrors every emotion that arises in your brain," Mayer adds.  In The Mind-Gut Connection, Mayer also tells the story of a patient who couldn't stop vomiting – a result of an overactive stress response in the brain.  But how does it work when it's the other way around? Studies show that more-often than not, traffic flows northbound on the "superhighway" that connects gut and brain, also known as the vagus nerve. Per Mayer, "90 percent of signals conveyed through the vagus nerve travel from the gut to the brain, while just 10 percent of the traffic runs in the opposite direction." You may have heard of serotonin, which acts as a chemical messenger and mood stabilizer – why antidepressants often increase serotonin levels to help with mood.  Astoundingly, 90 percent of serotonin is manufactured in the digestive tract and not the brain. Serotonin helps both with mood regulation and a smooth digestive process.  Practically speaking, certain diets can lower serotonin production. A diet lacking tryptophan (which helps with serotonin production) can increase the prevalence of depression in at-risk people. Tryptophan is found in many healthier food items like lean meats, rice, or bananas.  To be clear, we're not suggesting that simply not eating bananas or rice would lead to depression. However, this highlights the role our diet can play. If we're deficient in certain essential food items, it can play out in our emotional health.  While important, serotonin isn't the only mood stabilizing neurotransmitter.  Scientists have found that gut bacteria produce many other neurotransmitters such as dopamine, norepinephrine, acetylcholine, and GABA, which are critical for mood, anxiety, concentration, reward, and motivation.  This may lead to some head scratching, as it might seem to imply that we just operate on autopilot as the tiny "second brain" in our gut takes over. The key thing to remember is that while the microbiome may influence or impact how you behave, it doesn't rob you of your free will or cognition.  Most of the research around this has been done on animals, especially rats. By doing fecal transplants (gross, we know), experiments have shown that a change in microbiome composition has been linked to erratic or impaired behaviors, like mood disorders.  So, why should we care about any of this? On a practical level, our emotions affect the decisions we make. If we make food-related decisions from an anxious or frustrated place, it can only perpetuate the problem.  Say you're frequently stressed and use food to cope. Some deem this as comfort eating or comfort binging. And if you've ever been to a Thanksgiving dinner or Old Country Buffet, you know that comfort food entails lots of fat, salt, and carbs – components that (if consumed in excess) can affect your gut, along with other bodily functions. While it may be a temporary relief, the long-standing consequences were costly, as studies have shown doing this dampens our physiological response to stress. It's certainly not a novel concept that bad habits lead to bad outcomes, but the overall takeaway / reminder here is that our emotions play a huge role in our physical states, not just our mental states.  In a society in which mental illness affects millions of Americans each year, this is incredibly pressing information. What if a better understanding of the gut could lead to better treatments for depression and anxiety, or co-morbidities that come with them, like irritable bowel syndrome (IBS), or obsessive compulsive disorder (OCD)? There are of course other factors at play, but this groundbreaking research on our gut could be the key to unlocking issues typically deemed "only in our head."


"Emerging research suggests that the human gut microbiota may provide a potential avenue to enhance cognition," says an article published in the research journal Nutrients.  It should be noted before diving in that research is relatively new on this topic. And even the researchers in this study admit that though the findings are promising, they warrant further research. With that in mind, what are some ways that the overall composition of our gut flora (microbiome) could impact the way we think? One area that researchers are particularly fascinated with is the connection between gut composition and autism. If you are on the autism spectrum or know someone who is, please know that this is just an objective analysis of how gut imbalances could possibly lead to a higher prevalence of autism, not an indictment of autistic people. Extensive research through the years has shown that about 75% of people with autism have some kind of gut abnormality or imbalance, such as digestive issues or intolerances.  Sarkis Mazmanian, a researcher at the the California Institute of Technology, found that many people with autism have low levels of the bacteria Bacteroides fragilis. In his study done with mice, Mazmanian observed an improvement in behavior and a reduction in anxiety when Bacteroides fragilis was fed to them & incorporated into their gut microbiome. There's still some missing links there, but statistics like three-quarters of autistic people having some kind of gut abnormality is too high a figure to be ignored. But autism aside, how could the presence of certain bacteria in our gut microbiome affect how we process information and stress? Mayer highlighted the fact that a healthy gut can produce butyrate, a "short-chain fatty acid" produced when your gut breaks down dietary fiber – something sorely lacking from our typical diet. Unsurprisingly, dietary fiber is found in the foods we often skip, such as fruits, vegetables, whole grains, and legumes.  Butyrate has been linked to reduced anxiety, depression, and stress. And while this may sound like it belongs in the "emotions and mood" section, it's hard to separate cognition and emotion.  That isn't the case every time, but more a reminder that factors like stress and anxiety aren't just minor inconveniences – they have profound consequences on our overall health and longevity.  Back to the original point: researchers are trying to draw a direct link between gut microbial composition and cognitive status. Research from JAMA Neurology suggests a connection between gut composition and cognitive aging. That would explain why many have been fascinated with how something like a gut imbalance or lack of diversity could contribute to degenerative diseases like Alzheimer's or Parkinson's.  According to the research, data suggests that "the gut microbiota may be associated with cognitive aging, but must be replicated in larger samples and further researched to identify relevant pathways." If more conclusive evidence is found, the stakes are incredibly high. The number of Americans projected to be living with Parkinson's by 2050 is 14 million.  The toll on family morale and finances will be astronomical, but there's hope that these diseases are not totally unpreventable. Lifelong alterations in the gut microbe could play way higher of a factor than previously imagined.


Sadly, we now have to pay a premium on health and quality when we hit the grocery store. If you've ever paid a few extra dollars just to get the certified cage-free, vegetarian-fed, hormone and antibiotic-free, USDA organic eggs, you get the picture.  Even labels that tout a "better lifestyle" for the animals raised can be misleading or flat out false. What does vegetarian mean? Does cage-free mean they have a slightly bigger area to roam outside their own poop? To a large extent, it's not our fault that we have to hunt so hard at the store to find real food.  As Mayer put it, "in North America today, it's hard to get away from an unnatural diet, one that's full of sweeteners, emulsifiers, flavorings, and colorings, with extra fat, added sugar, and vital gluten, and loaded with calories." This is no exaggeration, as it's estimated that more than 35% of calories come from fat in the American diet. But the fat content itself isn't the main issue. Healthier diets, such as the Mediterranean diet, have similar proportions of fat overall.  However, the primary fat sources in said diet are nutritious foods like olives and fish. Per Mayo Clinic, "Olive oil provides monounsaturated fat, which lowers total cholesterol and low-density lipoprotein (or "bad") cholesterol levels. Nuts and seeds also contain monounsaturated fat." The positive cardiovascular and metabolic effects of the Mediterranean diet have a documented effect on reducing the risk of cancers and diseases like Parkinson's or Alzheimer's.  On the other hand, the American diet is characterized by high animal (saturated) fat consumption combined with excessive sugar and low plant consumption. (Not to mention an abundance of chemicals and additives)  Energy intake from ultra-processed foods sits at nearly 58% in the United States, compared with just 29% in France, for instance. Unsurprisingly, this has led to chronic inflammation, which ups the prevalence of disease.  In addition to the obvious side physical effects of this type of diet, as we've touched on in other blogs, they also have a profound impact on our microbiome.   While a diverse gut microbiome helps stave off obesity and promote a healthy, functioning body, an irritated, inflamed gut does the inverse.  How is it that the gut becomes irritated? Most of the gut contains "good" bacteria and can even function if "bad" bacteria gets in the mix. However, if that balance gets thrown off too much, it can create a harmful imbalance.  Our convenience-driven diet plays a major role in this. "Fast food consumption is associated with higher abundances of Blautia, Lachnospiraceae bacteria and Clostridium bolteae,"research has found.  While you may not be able to pronounce the names of said bacteria, their observed effects included gut permeability and intestinal inflammation.  "These bacteria turn to the mucus layer, leading to an erosion of the gut barrier.5 A high consumption of sugar and soft drinks combined with a low vegetable intake has already been linked to [Inflammatory Bowel Disease]," the study continued.  IBD, short for inflammatory bowel disease, goes beyond just stomach discomfort and can impact the colon and other parts of the intestines.  Without going too far into the nitty gritty, the point is that the Western (primarily American) diet has led to an abundance of people who are overweight or obese, which in itself entails an inflammatory state. By having a diverse microbiome, you'll have a higher prevalence of anti-inflammatory bacteria. So how do we tip the scales?  


We've established that our gut health has huge implications on our brains, mental states, and physical longevity. But genetic predispositions aside, how do we control what's in our control and make the best decisions for our optimal health?  In The Mind-Gut Connection, Dr. Mayer outlines practical, everyday choices we can make to foster a healthy gut microbiome. As a general rule, he says to imagine your gut microbiome like its own farm. You wouldn't want to inundate a healthy, thriving farm with harmful substances – so why would you treat the "farm" inside your body any differently? 

Avoid Highly Processed, Packaged Foods

Going off the last point, processed foods are the culprit in a myriad of health issues, yet they often masquerade as "healthy" options. Granola bars are a great example of this.  Chewy Bars, often a staple in lunchrooms and birthday parties growing up, look harmless as they tout health claims like "whole grain fiber" or "no high fructose corn syrup." On the flip side, they contain a considerable amount of saturated fat (the consequences of which we just mentioned), as well as 11 grams of sugar in one 140 calorie bar.  Products that line grocery store shelves are so processed to the point that they really shouldn't even be considered "food."  Many of these processed foods contain harmful ingredients and additives like artificial sweeteners, emulsifiers, and high fructose corn syrup. Beyond just looking at the ingredients list to see if a food item is processed, we should also consider how our food is being made, particularly when it comes to livestock. Industrial farming seeks to maximize output, no matter the cost, leading to situations where the animals we eat are consuming diets not meant for them, thus upping their need for antibiotics. Their gut microbiome is being hampered, and through consuming these animals, ours will be too.  Additionally, eating organic (as much as possible), will provide long-term benefits to your brain and gut health. Research argues that organic foods are better as they reduce exposure to pesticides, which have been known to be harmful to the gut.  While it's true that many grocery stores charge more for organic products, there are ways to still eat organically on a budget.  Moreover, just because something doesn't have the "USDA Certified Organic" label, doesn't mean it's not organic. Many small-farms that set up booths at farmers' markets don't have the budget to afford the "Organic" sticker, yet still raise their produce and livestock organically.  There are creative ways to eat organically without dropping stacks. Methods like shopping in bulk (Costco actually has a good organic selection!), growing your own produce, frequenting farmer's markets, or buying foods that are in-season.  And if none of those are an option, remember the clean fifteen, a list of produce with the least amount of pesticide use. These include vegetables like avocados or sweet corn. On the flip side, also consider the dirty dozen, produce you want to ensure is organic.

Incorporate Fermented Foods & Probiotics

Drinking kombucha (a fizzy fermented tea loaded with probiotics) may seem like a new fad reserved for trendy urbanites, but humans have been reaping the benefits of fermented beverages and foods for centuries. In fact, kombucha is said to have originated as early as 220 B.C. near Ancient China. The biggest perk of fermented foods is that they all contain probiotics, live microorganisms, bacterias, and yeasts that are largely beneficial for your body. Probiotics have benefits from improved digestion to increased immunity. Naturally fermented foods like kombucha, kimchi, sauerkraut, miso, tempeh, or yogurt, can provide a healthy dose of probiotics.  Moreover, these probiotic-rich, fermented foods aren't super expensive. A 32oz tub of nonfat Greek yogurt ranges from $3.00-5.00 depending on location, and a 14 pack of Humm Organic Kombucha costs about $28.00 at Costco, which comes out to be a modest $2.33 per bottle.

Eat Smaller Portions

The sheer volume of food we consume has taken a toll on our gut health. Unnecessarily large portion sizes have contributed massively to the rise of obesity in the United States:  Eating smaller portions more frequently instead of a massive breakfast, lunch, and dinner, can help the stomach to empty more quickly and reduce discomfort related to digestion. It also limits your overall caloric consumption, "keeping the amount in line with your body's metabolic needs and simultaneously [reducing] your fat intake," per Dr. Mayer.  Try switching it up by preparing snacks and smaller meals beforehand. It can be tricky between school, work, meetings, commute, family responsibilities, and extracurricular activities, but try to avoid just eating one massive meal that burdens your digestive tract.

Try Fasting

Going even further, consider periods of time of fasting (or not consuming anything but water). For some, fasting is a spiritual practice, but on a purely biological level it has benefits as well.  Research has found that the microbiome's composition shifts and changes after fasting. "There’s a rapid expansion of a particular bacteria (Akkermansia muciniphila) that's associated with positive health markers, like decreased intestinal inflammation and a healthier gut barrier," the article states.  Another 2018 study done on Salmonella typhimurium (a pathogenic bacteria) infected mice found that fasting led to the eradication of this bacteria, as well as colitis.  It also just gives your gut a break in general. As we just mentioned, the volume and prevalence of eating is much higher in our food-plentiful society, and our bodies weren't designed to handle the density of food coming in.  Giving the gut time to restore itself, particularly for those with "leaky" guts, is crucial. Leaky guts have a weakened lining, potentially allowing toxins to permeate it. It can lead to uncomfortability, bloating, and food sensitivities. Fasting may sound daunting, but you can ease your way in. Try skipping a meal or fasting everything but water for just a few hours. Take note of how your gut and overall mental/physical health feels after letting your body rest and reset. Here's how Mayer describes the benefits of this "reset": "fasting may also reset the many sensory mechanisms in the gut that are essential for gut-brain communication. Having no fat in the intestine for one or more days may enable vagal nerve endings to regain their sensitivity to appetite-reducing hormones.

Reduce Stress & Increase Joy

As mentioned earlier in the blog, stress can have a profound effect on our gut health. Negative emotional states can throw off the connection between our gut and brain, triggering stress hormones like norepinephrine and serotonin. Stress can affect digestion and make the intestinal barrier weaker, thus letting in more harmful bacteria and toxins. Both for gut and mental health, find activities, people, or purposes that bring you joy and reduce your stress levels. Whether that's finding a community, exercising, or taking up a hobby that promotes positive feelings, limiting the amount of stress in your life can have massive benefits.


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