It’s no surprise that dysbiosis, or an imbalance in your gut microbiota, affects your mood: it’s hard to be cheerful and happy when you’re experiencing digestive problems and discomfort. But scientists have shown that, in addition to mood, the activity of intestinal bacteria affects anxiety and stress. A balanced microflora helps the psyche cope with this.

The gut-brain connection
The vagus nerve, a key element of the autonomic nervous system that regulates the functioning of internal organs, connects the intestines to the brain. Thanks to this system, we breathe, swallow, and digest food without thinking. The vagus nerve helps move food through the gastrointestinal tract, stimulates the production of digestive enzymes, and lets us know how full we are. And this nerve also helps the brain control whether everything is in order with the intestines.
In addition to communicating via the vagus nerve, the microbiota can influence the brain through the bloodstream. For example, fatty acids produced by gut bacteria stimulate the production of serotonin, a neurotransmitter that keeps you in a good mood. And some probiotic bacteria even produce their own stress-relieving neurotransmitters, such as gamma-aminobutyric acid (GABA).

Stress, microbiota and depression
Stress triggers the release of the hormone cortisol and increases intestinal permeability. Because of this, endotoxins produced during the breakdown of bacteria can enter the bloodstream and trigger an immune response. Inflammation begins, and the nervous system responds to it, including mood swings. This can lead to symptoms of depression and anxiety.
Scientists have found that persistent inflammation often accompanies depression and anxiety, and taking anti-inflammatory drugs relieves these symptoms. In addition, mental state affects the composition of the microbiota and can lead to dysbiosis. For example, studies show that patients with depression have a much higher number of Bacteroidetes, Protobacteria and Actinobacteria, while the number of representatives of Faecalibacterium decreases. And the lower the number of this last group, the more severe the symptoms. Dysbiosis, in turn, weakens the protective function of the intestinal mucosa and provokes inflammation. And this only intensifies the mental state.
Diet against depression and anxiety
You can restore the balance of the microbiota and restore good mood if you adjust your diet. Pro- and prebiotics help restore the ratio of bacterial species and reduce the permeability of the intestinal mucosa. Studies have shown that such food improves the body's response to stress and reduces inflammation, while at the same time reducing the level of anxiety and symptoms of depression. Eat more plant foods.
Good gut bacteria love natural, plant-based foods that are rich in cellulose. When you eat prebiotics: fruits and vegetables, nuts, whole grains, or legumes, the bacteria produce butyric acid. This is an essential short-chain fatty acid that supports gut health. This helps prevent inflammation, which means preventing digestive problems and maintaining a good mood.
In dysbiosis, gut bacteria lack the nutrients needed to produce butyric acid and boost immunity. But diet can restore a healthy balance. For example, if you eat more plant-based foods or prebiotics, the good bacteria can get enough nutrition. They contain fiber, which is a source of essential fatty acids for the bacteria.
List of foods rich in prebiotics:

Probiotic bacteria have a positive effect on health, including mental health. These include bifidobacteria, lactobacilli, and lactococcus. They are already present in the intestines, but their proportion can be increased with supplements and fermented dairy products. Probiotics maintain a healthy microbiota balance and prevent dysbiosis. Studies have shown that certain strains of lactobacilli increase resistance to stress and anxiety, and taking probiotics may improve symptoms of depression. The gut and brain are closely connected and affect each other. Stress and dysbiosis worsen mood and affect the risk of anxiety and depression. And depression, in turn, can disrupt the balance of the microbiota and lead to the development of inflammation. A diet rich in pro- and prebiotics helps reduce inflammation, restore balance to the microbiota, increase resilience to stress, and alleviate depression and anxiety.