The bacteria that live in our intestines greatly influence how we feel. A balanced gut microbiota can keep anxiety and sadness at bay.
Have you ever wondered why when you are in love you feel butterflies in your stomach or when you are worried, a knot in your stomach? These curious sensations have to do with the connection between our brain, our intestine and the microorganisms that inhabit it.
The microbiota is the set of millions of microorganisms that coexist symbiotically in the intestine. Its composition is different from one person to another. We can host up to 300 different species of bacteria along with viruses, fungi and yeasts. We know that these microorganisms are very important for health, but what is surprising is that the microbiota can even influence mental health.
THE STATE OF YOUR GUT INFLUENCES YOUR MOOD
Gut bacteria are involved in brain development and condition personality and mood. People with behavior problems have been shown to have different intestinal flora. And those suffering from depression have more bacteria from the Bacteroidetes, Oscillibacter and Alistipes species, and less from the Lachnospiraceae family.
If we change the intestinal bacterial flora we can modify our mood. An example: a study published in Translational Psychiatry has found that a bifidobacteria probiotic makes healthy people feel less stress and improve their memory.
THE GUT AND BRAIN COMMUNICATE
The gut-brain axis functions as a two-way communication system and is being postulated as a possible explanation for neurological disorders such as Alzheimer’s disease, Parkinson’s disease, depression, anxiety, autism or multiple sclerosis.
This axis is formed by the microbiota, by the enteric nervous system (ENS) of the digestive system and by the central nervous system. The ENS is made up of between 200 and 600 million neurons that are found mainly in the wall of the intestine and connect to the brain through the vagus nerve, which runs from the brain stem to the abdomen.
In fact, the nerves that transmit stimuli to the brain and intestine have their origin in the same type of tissue: during fetal development, one part becomes the central nervous system (brain and spinal cord) and the other in the neurons of the Digestive SNE.
GUT BACTERIA PRODUCE NEUROTRANSMITTERS
Brain and gut influence each other. The brain sends messages to the gut (for example, when we are nervous and lose our appetite) and the gut sends messages to the brain. In this communication between organs, celestines are the substances that bacteria produce, such as short-chain fatty acids and neurotransmitter chemicals that travel through the vagus nerve highway.
Neurotransmitters are the substances that put our neurons in contact and transmit all the actions ordered by the brain, such as movement or behavior. They are also capable of modulating our emotions. Our happiness is closely linked to the brain’s chemical efficiency with which our neurotransmitters travel back and forth, communicating our emotions with our thoughts. Our faculties to feel, think and act, as well as to remain in harmony with ourselves, depend on the normal functioning of the brain and neurotransmitters.
Many intestinal bacteria are capable of synthesizing and releasing neurotransmitters. Therefore, they can directly or indirectly modulate what we feel and our behavior. When the production of neurotransmitters is excessive, deficient or null, behavioral problems and mental illnesses occur. Let’s see what the main neurotransmitters are.
Serotonin is known as the “happiness molecule.” The microbiota acts on the levels of the precursors of this neurotransmitter, such as tryptophan: if the levels of tryptophan are low, not enough serotonin is produced and, together with other factors, it can lead to depression or anxiety. Serotonin is also involved in sexual appetite, suicidal behavior, and the perception of pain. In the brain, it produces a state of well-being and in the intestine – where 95% of it is produced – it establishes the rhythm of digestive transit and regulates the immune system.
Tryptophan is an essential amino acid (we must get it from food, although some bifidobacteria can produce small amounts) and it acts as a precursor to serotonin and other neurotransmitters. But it doesn’t always turn into serotonin. It can also take the kynurenin pathway and convert to other metabolites like kinurenic acid or quinolinic acid.
Not all tryptophan. Imbalances in the microbiota can divert more tryptophan into the kynurenine pathway, reducing the availability of tryptophan for the synthesis of serotonin at the brain and digestive level, and causing a decrease in the “happiness molecule.”
The dopamine is another neurotransmitter whose synthesis is favored by the action of the microbiota. Participate in the pleasant and relaxing sensations. Its functions also include the coordination of certain muscle movements, the regulation of memory and the cognitive processes associated with learning. He even participates decisively in decision-making. In Parkinson’s disease there is a dopamine deficit, which is why we are studying how to modify the microbiota to achieve improvements.
HELPS CONTROL FEAR AND ANXIETY
The microbiota is involved in the release of GABA. This neurotransmitter is essential for modulating behavior: it stops the overstimulation of neurons and helps control fear and anxiety. Low GABA levels are linked to anxiety disorders, insomnia, sadness, depression, and even schizophrenia. Studies have shown that the administration of bacteria that improve the intestinal flora (probiotics) increases the availability of GABA, thereby improving anxiety control.
The microbiota is also involved in the production of certain short-chain fatty acids, such as propionate, butyrate, and acetate, which reach the hypothalamus through the bloodstream, where they regulate GABA levels. These fatty acids can also act as modulators of gene expression to the point that they can reprogram some brain functions and condition mood, according to Ted Dinan, professor of psychiatry at the University of Cork and an expert on the gut-brain axis. .
Norepinephrine is produced in response to stress to adapt to a threat, for example, if we are chased by a lion in the savannah and we have to run. When we are under chronic stress, the adrenal glands constantly produce adrenaline and norepinephrine. But there may come a time when they can’t keep up with production. Then we feel fatigued, moody and unmotivated, and it can even cause depression. How do we produce norepinephrine? Through tyrosine ingested with food and with the help of intestinal bacteria.
THE IMMUNE SYSTEM IS INFLUENCED BY THE MICROBIOTA AND THE BRAIN
There is another remarkable element that participates in the interaction between the neurons of the brain and intestine and the microbiota, and that has a lot to do with our state of health: the immune system.
A very important part of our defense system is located around the intestinal lumen, where it controls the presence of pathogens and interacts with the microbiota to regulate different functions.
The immune system works to maintain balance on the intestinal surface. It generates two-way communication with the central nervous system, which translates into an effect of the microbiota on the central nervous system itself and on the brain. The result is changes that affect our physical and emotional reactions. The microbiota and probiotic interventions can thus have a very positive direct effect on the immune system.
HOW THE MICROBIOTA-BRAIN RELATIONSHIP WORKS
Brain and gut influence each other. When we suffer stress, our intestinal flora suffers, which reverts to an inflammatory process that, in turn, impairs cognitive functions and worsens symptoms. But if we take care of the composition of the microbiota, we will better assimilate the nutrients and produce neurotransmitters that make us feel balanced. We can act both on the intestine and on the brain so that the system works perfectly.
- With a healthy microbiota, “molecules of happiness” are released, mood improves, sleep well, and more physical energy is available. The levels of dopamine and serotonin are optimal and the assimilation of nutrients at the intestinal level, ideal. The appetite is well regulated and the intestinal tissues in good condition, thanks to the action of prebiotic and probiotic foods.
- On the other hand, with a microbiota in dysbiosis, an excess of adrenaline and norepinephrine is generated, it is more likely that symptoms of depression and stress appear, inflammation reaches the neurons and food toxins can pass into the blood, because due to intestinal inflammation increases the permeability of its walls.
