How microorganisms control our emotions

Image by Darko Djurin from Pixabay

We live in a microbial world. Microbes have lived on Earth for hundreds of millions of years longer than humans, and at all times our body has interacted with their environment. The human microbiota is a collective term for the trillions of microorganisms that live in the gastrointestinal and genitourinary tracts, lungs, and on the surface of the skin. Microorganisms are involved in many physiological and biochemical processes in our body. Including those that influence our behavior.

We don’t even know, but microorganisms can change our behavior:

  • Eating behavior
  • Cognitive ability
  • Social behavior
  • Sense of anxiety
  • Stress resistance

Eating behavior
There are several mechanisms by which the microbiota can influence our eating behavior. The microorganisms living in the intestine produce short protein molecules. Their activity is similar to proteins that regulate human appetites, such as ghrelin, leptin, galanin, and others.

Another likely mechanism by which the microbiota can influence feeding behavior is related to a change in a person’s ability to taste food. With obesity, there is often a decreased sensitivity to sweets and fat. This leads to the need to increase the consumption of sweets and fat in order to achieve the usual level of taste perception. Such changes in taste sensitivity are often accompanied by an abnormal composition of the intestinal microflora. Taste transmission signals are known to be mediated through taste buds on the tongue. Interestingly, in addition to the influence of the microbiota, taste sensitivity also depends on the genetic characteristics of our body. Some gene variants are associated with changes in the density of these receptors or their functional activity. For example, polymorphisms in the CD36 gene are associated with sensitivity to fatty taste, and in the GLUT2 gene, to sweetness.

You can learn about your individual sensitivity to fatty foods and sweet tastes by doing genetic analysis and analyzing the CD36 and GLUT2 genes.

Cognitive ability
The gut microflora also affects our cognitive abilities. The detailed molecular mechanism of this effect is not fully understood, however, it is assumed that a possible mechanism is associated with a change in the expression (production) of the brain neurotrophic factor and neurotransmitters (such as serotonin and glutamate). In particular, a decrease in the expression of the brain neurotrophic factor BDNF leads to a decrease in the number of contacts between neurons and disruption of the processes of neuronal division in the dentate gyrus of the hippocampus. These changes lead to decreased response rates, cognitive flexibility, and neuronal activity in many regions of the brain and are often accompanied by impaired gut microflora composition in adults. Microbiota composition in one-year-old infants is also associated with cognitive development, which was assessed using the Mullen Early Learning Scales.

Further evidence of the link between the microbiome and cognitive ability is that therapy with a variety of probiotics (such as Lactobacillus) often leads to improvements in cognitive tests. In women, consumption of fermented milk products supplemented with a probiotic has been shown to modulate activity in areas of the brain involved in cognitive performance and memory.

Social behavior
The influence of the microbiome on social behavior has been traced in various studies, both in animals and in people with various mental diseases, which are characterized by changes in the pattern of social behavior (autism spectrum disorders, schizophrenia, bipolar disorder). It has been shown that the normalization of intestinal microflora in children and adolescents with autism spectrum disorders leads to a decrease in the symptoms of this disease.

The detailed mechanism by which the microbiome influences social behavior is not yet known. However, it has been proven that the intestinal microflora is capable of synthesizing various biologically active substances that affect vascular tone and the development of inflammatory processes. A number of these substances are able to penetrate the blood-brain barrier and affect the activity of the production of certain neurotransmitters in the brain.

Anxiety / Stress tolerance
Our resilience to stress also depends on the microbiome. Studies of brain activity using magnetic resonance imaging have shown that the appearance of pathogenic bacteria in the gut microbiota correlates with how strongly neurons are activated in response to a stimulus (emotional imagery). It should also be noted that people who are depressed or under chronic stress are more likely to suffer from gastrointestinal disorders.

Thus, the microbiota influences a wide range of manifestations of our behavior. This interaction occurs both through peripheral effects by modulating the activity of the gastrointestinal tract, inflammation, and by altering the production of some neurotransmitters and other regulatory molecules in the brain.

How should you eat in order to maintain normal intestinal microflora?

  • Eat as many of a variety of foods as possible that contain fiber (prebiotics)
  • Incorporate Whole Grain Meals into Your Diet
  • Eat fruits and vegetables rich in polyphenols (broccoli, spinach, capers, strawberries, blueberries, and others)
  • Take probiotics

What factors have a negative impact on the intestinal microflora?

  • Eating large amounts of carbohydrates and fats
  • Lack of fiber
  • Taking antibiotics
  • Taking various medications, such as histamine H2 blockers, proton pump inhibitors, and nonsteroidal anti-inflammatory drugs
  • Stress
  • Passive lifestyle
  • Hormonal changes

Remember that intestinal disturbances associated with changes in the composition of its microflora can cause health problems and negatively affect mood. Nonetheless, the microbiome is flexible and dynamic. And, despite the fact that many factors can unbalance it, the microflora can recover within a few weeks, subject to the rules of nutrition and a healthy lifestyle. And knowing the genetic characteristics of your body’s gustatory sensitivity and the principles of the main brain neurotransmitters will help you even better adjust your diet, control your well-being and cope with stress.


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