Due to an improved understanding of the body and the interconnectedness of individual body systems, we are gradually moving beyond the traditional view of the body, which treats body systems as separate and independent entities with specific functions.
One of the most interesting and complex connections between body systems is the interaction between the brain and the gut. As we will see below, these are not isolated parts of the body, each with its functions, but they are closely linked, and their connection is crucial for the overall health and well-being of the body. The intestines no longer function only as digestion but also influence the functioning of all organs (liver, brain, skin…).
The close connection between the gut and the brain becomes particularly evident in stressful situations. Chronic stress is not desirable, but it is an increasingly common companion of modern life and has an impact on our mental and physical well-being. However, with proper strategies, we can reduce its effects.
The Science behind the Gut-Brain Connection Theory
The brain and the gut are connected through the gut-brain axis, a communication pathway that facilitates the transmission of information in two directions: 20% of information travels from the brain to the gut while 80% of information is transmitted from the gut to the brain. Communication between the brain and the gut occurs through several parallel pathways, but also including:
- the nervous system (connection between the central nervous system and the enteric nervous system via the vagus nerve);
- the hormonal system;
- the immune system;
- metabolites from the gut microbiota, which reach the brain through the three aforementioned pathways.
You have probably already noticed this close connection in everyday life. For example, when an important exam at university is approaching, the intestines become more active, and that is not a coincidence. Our emotions are also reflected through the feeling of “butterflies” in the stomach, which is a consequence of this mysterious communication between our brain and gut.
Enteric Nervous System – the Gut as Our Second Brain
Have you ever heard of the expression that “the gut is our second brain?”
Nerves containing around 100 million neurons are part of a vast interconnected network found in the wall of the intestine or digestive tract. This nervous system is called the enteric nervous system, and due to its fascinating ability to function independently, as it is not under the control of the central nervous system, it is also referred to as the “second brain.” Because of its complexity, it can be compared to the spinal cord.
The main task of the enteric nervous system is the regulation of intestinal functions such as the secretion of digestive juices, the action of peristalsis – rhythmic contractions that propel food through the digestive tract, the release of various neuropeptides and hormones, the regulation of blood flow, and the absorption of nutrients.
However, its role does not end with digestion. The enteric nervous system is closely connected to the brain through the vagus nerve. The intestines communicate with the brain via neurotransmitters (serotonin, dopamine, GABA) produced by intestinal cells, and the intestinal microbiota also communicates with the brain.
The Vagus Nerve, a Two-Way Communication Link between the Brain and the Gut
The enteric nervous system is connected to the brain through the vagus nerve, also known as the “information highway,” as it is the fastest, direct, and two-way link between the brain and the gut.
The vagus nerve detects mechanical, chemical, and hormonal signals in the intestines and transmits them to the brain, which then takes appropriate measures to maintain internal balance. It continuously monitors the state of the intestines, sending information about the composition of the gut microbiota, changes in pH values, nutrient levels, inflammatory processes, and more to the brain.
The vagus nerve also conveys commands from the brain to the digestive tract and plays a crucial role in the peristalsis of the digestive tract, the secretion of digestive juices, and the absorption of nutrients. As part of the parasympathetic nervous system, it functions best in a relaxed state. Read on for information about the negative impacts of stress on the digestive tract, which primarily occur due to the limited action of the vagus nerve.
The Immune System as a Communicator between the Intestines and the Brain
The intestines are not only the center of digestion but also the center of the immune system, as more than 70% of immune cells are located in the intestines. Immune system cells constantly monitor events in the gut, identify the composition of the microbiota, and communicate with the brain by releasing inflammatory or anti-inflammatory signaling molecules, such as cytokines and chemokines.
The interaction between the immune system in the intestines and the brain is based on the connection with microglia, immune system cells located in the brain and spinal cord. Negative changes in the composition of the intestinal microbiota affect the activation of microglia and trigger inflammatory processes that can cause neurological disorders.
On the other hand, a healthy and diverse intestinal microbiota with beneficial metabolites such as short-chain fatty acids acts protectively on microglia and maintains the proper functioning of the brain.
Transfer of Information from the Intestines to the Brain through the Endocrine System
The connection between the intestines and the brain through the hormonal system occurs in several ways. One of them is through intestinal hormones (e.g., CCK, GLP-1) released from intestinal cells and transmitted to the brain via the vagus nerve or by directly entering the circulatory system.
Additionally, the intestinal microbiota produces hormone-like metabolites that enter the bloodstream and act on receptor sites in the brain. Furthermore, the hypothalamic-pituitary-adrenal HPA pathway is one of the key ways information is exchanged between the brain and the gut. The primary task of activating this axis is the release of cortisol to prepare the body for “fight-or-flight,” which can have a significant impact on the physiology of the intestines in the case of chronic stress reactions.
The Impact of Stress on the Gut-Brain Axis Function and Digestive Issues
It is difficult to avoid stress in today’s fast-paced life. Stress has become an inseparable part of our daily lives, whether it is waking up in the morning, commuting to work, or dealing with responsibilities.
Although we frequently use the expression “I am stressed,” many of us probably do not fully understand what it exactly means.
Essentially, stress is the body’s physiological response to negative external or internal stimuli present in our daily lives that disrupt the internal balance in the body. Stress is manifested in various ways, from physical exertion (insomnia, intense workouts) to dietary factors (lack of food, allergies) and emotional or social stressors (career pressure, difficult relationships).
However, stress is not necessarily negative. The purpose of stress reactions, which have evolved over thousands of years, is adaptation and the restoration of internal balance to its state before the stimulus has occurred. Acute stress is crucial for survival and motivates us to achieve goals. When the danger passes, the body returns to a balanced state.
On the other hand, prolonged exposure to stressors, even in smaller doses, is detrimental to both physical and mental health. The body in a state of chronic stress is not in balance, leading to long-term negative effects on the immune, hormonal, cardiovascular, and central nervous systems.
Chronic stress represents a significant health issue in society. Among the noticeable negative effects of chronic stress are neuroplastic disturbances, such as depression and anxiety, affecting more than 25% of individuals. However, the digestive tract is also not immune to the impact of stress factors, as both acute and chronic stress can affect its function.
Stress has numerous negative effects on the physiology of the intestines, including:
- changes in the mobility and peristalsis of the digestive tract;
- increased permeability of the intestinal wall and changes in the function of the intestinal barrier;
- negative effects on the composition, diversity, and function of the intestinal microbiota;
- negative effect on the secretion of digestive juices (hormones, enzymes, and gastric acid);
- increased visceral sensitivity to pain (hypersensitivity);
- negative effects on the ability to regenerate the intestinal mucosa and mucosal blood flow;
- activation of immune system cells that release various inflammatory mediators.
Exposure to chronic stress leads to changes in the functioning of the gut-brain axis, which can result in the development of various gastrointestinal disorders, including inflammatory bowel diseases (e.g., ulcerative colitis), irritable bowel syndrome, chronic constipation or diarrhea, peptic ulcer, heartburn, and GERD (gastroesophageal reflux disease), and even allergies or food intolerances.
The bidirectional connection between the gut and the brain is also reflected in the fact that exposure to chronic stress causes changes in parts of the brain responsible for the perception of pain in the intestines, and gastrointestinal problems influence the development of mental disorders. For example, research suggests that irritable bowel syndrome may be a cause of anxiety and depression.
The Gut Microbiota Acts as a Defensive Mechanism against the Effects of Stress
It is interesting that the gut microbiota directly responds to stress stimuli. Stress causes changes in hormones, neurotransmitters, and inflammatory molecule levels that directly or indirectly affect the composition and diversity of the gut microbiota.
For example, the neurotransmitter noradrenaline, released during stressful situations, influences the growth, virulence, and motility of both pathogenic and commensal bacteria. Therefore, stress can affect the extent of infection through the microbiota.
On the other hand, the gut microbiota is beneficial because it acts as a kind of “protective mechanism” and helps mitigate the impacts of stress on our bodies. The gut microbiota can also influence how we perceive pain. Some probiotic bacteria, for instance, reduce the perception of pain and alleviate the increased gut permeability caused by stress.
How Can the Impact of Stress Be Alleviated through Diet?
Although stress is ubiquitous and an inseparable part of our daily lives, there are tools that we can use to manage it, mitigate its effects on the digestive tract, and preserve overall well-being. Improving stress management skills allows us to become more resilient to the effects of stress.
Areas to which we should pay more attention to better manage stress include:
- maintaining a balanced diet;
- taking care of sleep hygiene;
- incorporating relaxation and breathing techniques into our daily life;
- engaging in physical activity.
All these factors can help reduce the feeling of stress and enable us to become more resilient to its effects.
The Role of a Diet in Stress Management
While there is no magic food that can solve all stress-related issues, our dietary habits play a significant role in the perception of stressful situations, the body’s response to everyday life pressures, and the reduction of negative impacts of stress on body systems, especially the digestive system.
Stress alters our physiological needs. When under stress, our body consumes more energy, requires more oxygen, and needs more nutrients such as vitamins, minerals, proteins, and healthy fatty acids necessary for hormone synthesis, tissue renewal, and enzymatic activity. One of the harmful effects of stress is also the depletion of nutrients. At the same time, poor digestive system function and inadequate absorption of ingested nutrients worsen the condition of nutrient deficiencies.
Excessive cortisol production also leads to an increase in inflammatory markers and oxidative stress, which need to be reduced if we want to avoid the negative effects of stress.
Similarly, our dietary habits change under the influence of stress, as stress affects food choices and the quantity of food consumed. On the one hand, we have increased needs for nutrients and reduced absorption, while on the other hand, we choose food that is low in nutrients, and rich in saturated fats and sugar, which negatively impacts inflammatory markers and does not provide the body with necessary nutrients.
What should we pay particular attention to during a stressful period?
- Complex carbohydrates should be consumed. They will help regulate blood sugar levels, prevent energy crashes, contribute to maintaining a good mood through the synthesis of serotonin – the happiness hormone, help preserve the intestinal barrier and ensure the proper functioning of the digestive system. Complex carbohydrates can be found in whole grains, legumes, fruits, and vegetables.
- Ensure your body receives an adequate intake of proteins. During stressful periods, there is an increased need for amino acids such as tryptophan, phenylalanine, and tyrosine. Tryptophan is an essential amino acid and a precursor to serotonin. Tyrosine, derived from phenylalanine, serves as a precursor to many neurotransmitters crucial in stressful situations, such as norepinephrine and dopamine. One important effect of tyrosine is preventing a decline in cognitive functions that can result from prolonged stress. Amino acids are found in milk and dairy products, egg whites, lean meat, fish, and soy, as well as sesame and pumpkin seeds.
- It is also beneficial to increase the intake of vitamin C, B-complex vitamins, and magnesium.
Magnesium is an essential mineral that participates in over 300 enzymatic reactions and plays a crucial role in regulating blood sugar levels, heart function, blood pressure, and energy production. It is also known as the “relaxation mineral” because it aids in muscle and central nervous system relaxation. Maintaining an adequate level of magnesium can contribute to a sense of calmness and help alleviate anxiety. Stress can lead to increased excretion of magnesium through urine, potentially resulting in a deficiency of this mineral. For this reason, it is important to ensure an adequate intake of magnesium through diet. Rich sources of magnesium include nuts, legumes, whole grains, dark leafy vegetables, and Donat natural mineral water.
B-complex vitamins play a role in maintaining the health of the nervous system, help regulate blood sugar levels, and support the function of the adrenal gland, which is particularly stressed during periods of stress. Vitamin B5 (pantothenic acid) is especially important as it participates in the production of stress hormones in the adrenal gland. Vitamins B1, B6, and B12 are crucial for the synthesis of neurotransmitters that regulate mood.
Chronic stress can deplete these vitamins, affecting mood, irritability, cognitive functions, and the body’s response to stress in the long term. B-complex vitamins can be found in legumes, nuts, leafy vegetables such as broccoli, asparagus, and spinach, as well as in fish and lean meat.
Vitamin C is not only important for the optimal functioning of the immune system but is also present in large quantities in the adrenal gland, indicating its significance for its proper functioning. The need for vitamin C significantly increases during stressful situations because this vitamin is an important enzymatic cofactor for the synthesis of stress hormones.
Due to the increased need for vitamin C, our susceptibility to infections and other illnesses increases during stressful periods, especially if our body lacks this vitamin. Surely you have already experienced ‘a drop’ in your body’s resistance after a stressful period. Additionally, stressful situations often lead to increased production of free radicals, and vitamin C is one of the most crucial antioxidants that reduces oxidative stress.
- It Is Important to Pay Attention to the Intake of Anti-Inflammatory Foods and Foods Rich in Antioxidants.
Stress can increase inflammatory markers and the production of free radicals. In the case of mild oxidative stress, our cells defend themselves against damage using their own antioxidant protection. However, in the case of significant oxidative stress, it is important to support the body by increasing the intake of antioxidant-rich foods. For this purpose, we can use the simple rule of a “colorful plate.” Antioxidants are often found in colorful, vibrant foods, especially in dark green, purple, and blue foods.
- Conscious Consumption of Food Is an Important Element of Proper Digestion
In addition to a proper diet, conscious consumption of food is also important for better digestion.
Digestion often does not function optimally during stressful situations because the vagus nerve is part of the parasympathetic nervous system, which works best when we are relaxed. Poor digestion is manifested by reduced secretion of digestive juices, decreased blood flow to the digestive tract, weaker intestinal mobility, and disrupted nutrient absorption… All of this leads to abdominal pain, bloating, chronic constipation, and nutrient deficiencies. To improve digestion during stressful times, we can utilize some techniques of conscious food consumption, which are generally recommended.
These techniques also promote awareness of food choices and the amount of food consumed, which can help prevent overeating and control diet during stressful situations. You can read more about conscious diet tools in this article: https://www.donat.com/mindful-eating-for-better-digestion/
The role of the intestines and intestinal microbiota surpasses all our previous knowledge and demonstrates a crucial impact on the functioning of every organ. Among the most interesting interactions is the connection between the brain and the gut, which is much stronger than we can imagine. Stress affects the function of the gut and the brain and has become an inseparable companion of modern life.
The close relationship between the brain, gut, and stress has significant consequences for our overall health and well-being. However, it is important to understand that a balanced diet, relaxation techniques, and appropriate physical activity can help alleviate the effects of stress on the digestive system and, in turn, improve overall physical well-being.
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