Consider this: How your stomach affects your brain.

Think about it... You recently won the lottery for ten million dollars. Congratulations. You've just finished the warmest, tastiest chocolate brownie ever made.You just finished having sex. And you just accomplished all three of them at once. Likewise, congratulations to you. Our brains create substances known as neurotransmitters in these circumstances, which offer us these wonderful feelings of vigour, excitement, and joy. And we wouldn't experience these feelings in such wonderful conditions if we didn't have these chemicals inside us. Imagine this instead: You were recently let go. You are about to take a test. You're depressed. Instead, in these circumstances, our brains release various chemicals that cause us to feel agitated and apprehensive. How we feel and the substances in our brains regulate the ups and downs of life. We all have this important organ inside of us that regulates everything we experience, think, and do. But until I learned that this could not be the case, as a scientist, I've consistently found it difficult to understand that every feeling, idea, and movement we have is governed by a three-pound, wet mass of cells within our heads. The story I want to tell you today reveals an amazing discovery in human physiology: each of us has a second brain, an organ in our bodies that regulates many of our bodily and mental functions just as effectively as the cognitive in our heads. This second brain may be the key to understanding the worldwide epidemics of modern diseases, ranging from being overweight to cardiovascular disease and possibly even mental health. But first, I want to briefly describe my background to introduce you to this story. In the household of psychologists, I was raised. My sister also has a PhD in psychology, and my parents and dad are university psychology professors. I, therefore, wanted to pursue a different course of study when I went to university. I wanted to learn something new because I had already learned enough about the brain and its operation at home. I thought about my interests and discovered that I had a strong interest in eating since I was a very young child. I cherished eating. So I decided to research human nutrition. And this was fantastic because it allowed me to learn about food, how it impacted our health, how it may create sickness, and—most importantly—how we might use it to stop and avoid it. This narrative begins in Russia in 1845 with the conception of a fascinating boy who would grow up to be an amazing man but would later be ignored by history and health. Ilya Mechnikov was attracted by nature, as well. By the time he was eight years old, he was making notes about every living creature in his lush backyard garden. He excelled in research to the point where he identified the function of phagocytes, important immune system cells, for which he was awarded the Nobel Prize in 1908. But via a story of discovery, mortality, and self-experimentation, his science after receiving the Nobel Prize was even more important to the comprehension of human health. You see, there is a connection between everyone in this room. Our mothers carried all of us during the first nine months of our lives. And you were the only live creature in what was a sterile atmosphere. However, when you entered this world, you were covered with an invisible layer of helpful bacteria from your mom's birth canal. And as these bacteria multiplied, they formed the microbiota, or microbiome, now an invisible organ weighing three pounds, or the brain inside your big intestine. This unseen organ has expanded to the point that just 10% of the living things in your body are currently derived from human cells, and 90% are bacteria. Therefore, you are less human and more bacterial.Your gut's microbiome has a diversity comparable to the Amazon jungle. There are countless species, each with a unique function. And the life and vitality of this rainforest are crucial to your health. Your gut bacteria help you digest some foods, make necessary hormones and vitamins, respond to medications and infections, and regulate your cholesterol and blood sugar levels. Meaning that your chance of developing certain diseases, such as diabetes, obesity, and possibly osteoporosis, can be strongly influenced by the species of microbes in your gut. Almost every function in your body involves them. They operate similarly to a second brain. Ilya Mechnikov might have come to this conclusion on his own in 1892. At the time, a horrific cholera epidemic in Paris, France, claimed thousands of lives. He naturally felt that the best way to explore this as a scientist would be to consume cholera broth. Amazingly, he stayed healthy. As a genuine scientist, he realised that he needed to expand his sample size, and so enlisted a colleague to carry out the same task. This man also avoided falling ill. But when he persuaded a second coworker to follow suit, the unfortunate man fell unwell and almost died. By examining cholera under a microscope, Metchnikov discovered that while some kinds of bacteria from the individual's intestines inhibited cholera from spreading, other species encouraged and spurred it. Later, he asserted that the microbiota, or bacteria, in our guts were crucial for human health and that the proper balance of these germs may help us fend off disease. However, it was widely believed then that the human stomach was a dangerous storehouse of toxins. In individuals who experienced abdominal discomfort, surgeons had even started removing entire segments of the human intestine. Since Mechnikov passed away in 1916, his theories regarding the benefits of our gut microbes have been lost to time. Antibiotics were found ten years later and dramatically overused. C-sections spread in frequency. Diets shifted towards the West. Our gut rainforests were transformed into desolate wastelands due to a century-long war against bacteria. The concepts of this Nobel Prize laureate were lost to time. Recently, some of these implications were discovered. In America, one in three babies is delivered via C-section, which means they do not receive the initial inoculum or bacterial coating that has evolved to be in the mom's birth canal. As a result, there is an up to 25% greater chance of developing obesity, asthma, immunological deficiencies, and intestinal inflammation later in life. Instead, they are first covered with other germs on the skin or within the hospital surroundings. Fortunately, we've come to understand recently that, in order to maintain our physical health, we need to rebuild our connection with gut microorganisms. We continue to grossly undervalue their function as our backup brains, nevertheless. I'm doing a study on this as well. And I first discovered this through reading an amazing mouse story. A fascinating thing occurs when mice are colonised by the parasite Toxoplasma gondii: they stop being afraid of cats. In actuality, they start to attract cats. In essence, they become a little crazy and, unfortunately for them, frequently become cat food. As a result, the animal's brain is taken over by the microorganism it consumes, altering the animal's thinking and behaviour. So, by penetrating the bacterial jungle in our intestines, we've started to make some amazing findings that forever alter how we view microorganisms. You see, there are a variety of physical and biological connections between our stomachs and brains. First, the vagus nerve transmits impulses in both directions and physically connects our intestines to our brains. Interestingly, even if this is broken, our intestines continue to function normally without access to the brain, indicating they may have free will. Second, our brains include 100 billion neurons that communicate with one another constantly to instruct our physical beings how to function and behave. Interestingly, there are 100 million neurons in our guts. Thirdly, because our immune systems are centred on our microbiomes, a disruption here can trigger subtle immunological responses across the body, which can impact brain health if they continue for a long time. Do we recall the chocolate-eating, lottery-winning womaniser sitting in the front row? He showed us how neurotransmitters, which are substances that may alter our thoughts, actions, and emotions, work. As it turns out, most of these transmitters are also made in our stomach, but none more so than serotonin, the natural antidepressant, of which 90% is made there and less than 10% in the brain. Consequently, your thoughts and behaviours may be influenced by the kinds of bacteria that live inside of you. Has stress ever caused inside issues for you? Ever experienced a gut instinct? Or perhaps stomach aches? You might want to give that some thought. As you can see, I've started to study not just one brain but two brains despite my naive hesitation as a youngster. The gut-brain connection fascinates us at the APC Microbiome Institute in Ireland. We research how modern diets and lifestyles affect this gut-brain connection and how to create interventions that specifically target the microbiota to prevent and treat chronic diseases. For instance, we've demonstrated that the kinds of lipids you consume throughout your life significantly impact the kinds of bacteria that settle in your intestines. Additionally, we've demonstrated that feeding animals with particular bacteria strains can improve their memory, stress-related behaviour, and stress hormone levels. We've also compiled lists of meals that may serve as prebiotics or meals that can encourage the growth of beneficial bacteria in our intestines, along with the contributions of other researchers from across the world. The fact that our health relies on feeding ourselves and the other living microbes inside us is exciting to me. This means that future attempts to target and cure chronic diseases, including those that affect brain health, may depend on feeding or targeting our gut microbiomes. Ilya Mechnikov might have known this himself, and it turns out. He was married quite early in his life, but his wife succumbed to the disease quickly and passed away. Metchnikov overdosed on opium due to the anxiety and trauma caused by this. Thank goodness he lived. He then got remarried, and when his new wife was ill with fatal typhoid fever, he injected himself with the illness transmitted by ticks. He thankfully made it through again. Metchnivok didn't start learning about and appreciating the microbiome until after this. He relocated to Paris to work at the Pasteur Institute, where he started to postulate that having the proper balance of microorganisms in the gut could aid in preventing sickness. He then wrote several books and talks on how to do this and extend life. Notwithstanding the pressure and mental anguish he had previously gone through, he devoted the remainder of his life to studying ways to extend human life and became obsessed with it. He started researching an intriguing group of individuals in Eastern Europe that lived extraordinarily long lives. He noticed that they all consumed daily amounts of bacterially fermented milk and hypothesised that this was a factor in their longevity. Interestingly, he started consuming this bacterially fermented milk himself and appeared to lead a healthy life free of the stress and mental anguish he'd known in his early years. Perhaps it was just a coincidence. According to him, his time in Paris was the most joyful of his life. But at 71, Metchnikov passed away in France in 1916. Throughout France, at the moment, the average lifespan is 40. We must all develop a higher respect for the bacteria that live inside of us as humans. Inadvertently fighting germs during the past century has caused their extinction and created an upsurge in current diseases. I'm researching how to repair our relationship with bacteria and how to do so to avoid or alleviate chronic diseases while I'm here as a Fulbright. But I believe we all have the capacity and duty to continue Ilya Metchnikov's legacy. Not only to restore his lost scientific discoveries but also to adopt his ambition to increase the length of healthy human life. We can all promote the lives of the bacteria we've developed to coexist with by increasing our knowledge of the risks and advantages of C-sections, limiting the use of needless antibiotics, or adopting a diet and lifestyle that is friendly to the gut. So picture this: Think about the last time you ate chocolate, won the lotto, took an exam, or got the boot. Imagine that a secret organ you knew little about could regulate your thoughts, emotions, behaviour, and health. Ilya Metchnikov worked to promote healthy microbiological and healthy human life. By repairing the link between man and microbe, I believe we can all make a difference in this battle that is worth fighting for the health of both present and future generations as well as our own. There are several things to consider.