The connection between the gut and the brain is more complex and multifaceted than we can imagine. The intestines play a key role in protecting against harmful bacteria and promoting beneficial bacteria. The large intestine is home to a huge number of bacteria – for each gram of intestinal content there are as many as 1 trillion of these microorganisms, which gives a total of about 40 trillion bacteria, which is more than half the number of cells in our body. Most of our gut bacteria belong to 30-40 different species, creating a complex intestinal microflora. These bacteria not only benefit from the warmth and food we provide, but also convert fiber into short-chain fatty acids, influence metabolism and help synthesize vitamins P and D. However, an imbalance in the intestinal microflora can contribute to the development of autoimmune diseases.
Scientists are constantly examining the interactions between the intestinal microflora and our body. One of the most interesting discoveries is the ability of gut bacteria to influence our brain and behavior. The processes that take place in the intestines are extremely important for our body. For example, if the intestines are empty, this information is transmitted to the brain, which perceives this signal as hunger and tells us to eat. Moreover, if the intestines encounter pathogens, the brain is also informed. Communication between the gut and the brain occurs through the central nervous system and the enteric nervous system, which regulates gut function.
Researchers have asked themselves whether intestinal bacteria can influence our mental well-being and behavior? There is a connection between the gut and stress. All types of stress are regulated by the hypothalamic-pituitary-adrenal system. The hormone cortisol, known as the “stress hormone,” affects the brain, gut and other organs in various ways. When we feel stress, the brain sends signals to intestinal cells, including epithelial cells, immune cells, neurons of the enteric nervous system, and enterochromaffin cells, which produce and store serotonin. These cells, constantly under the influence of intestinal bacteria, communicate with each other in two directions. There is research suggesting that bacteria can influence our behavior. For example, patients with hepatic encephalopathy who had movement and neuropsychiatric disorders reported improved health after taking antibiotics. In another study, gut dysbiosis was linked to autism. It was found that children suffering from this disease had an unusual and less diverse intestinal flora. In addition, scientists have found that gut bacteria can activate the vagus nerve, which affects most abdominal organs. Bacteria also directly affect neurons of the enteric nervous system. Researchers hypothesized that gut bacteria may influence the levels of neurotransmitters involved in the interaction between the gut and the brain. Discovering this link is the first step in understanding the role of bacteria in diseases such as autism.
