-Doctor, I haven’t felt well for months, I have anxiety, it’s hard for me to concentrate.
And how does your gut feel?
-Sorry, What does one thing has to do with the other?
-Very much, let me tell you…
You may have heard that our brain and gut are connected. The axis gut-brain describes a physiological concept that integrates all neural, endocrine, nutritional and immunological signals between one system and another.
We already know the importance of the microbiome for the digestive system to function properly.
However, it is now that we are beginning to discover the relationships between the central nervous system and the gastrointestinal system.
Certain neurological and behavioral diseases have been associated with increased intestinal permeability and the passage of inflammatory compounds (called cytokines) and neuromodulators into the bloodstream, and from there to our brain.
In fact, some bacteria are capable of producing dopamine, serotonin or norepinephrine, key in physiological processes, memory, learning and behavior.
Thus, the alteration of the intestinal microbiota can modify our behavior and has been associated with central nervous disorders, such as autism, depression or anxiety behaviors.
What are they and how do they act?
The term psychobiotic was coined in 2013 by a group of researchers from the Food Pharmaceutical Center in Cork (Ireland).
They defined it as “a living organism that, when ingested in adequate amounts, produces a health benefit in patients suffering from psychiatric illness.”
Therefore, psychobiotics differ from probiotics in that, due to their properties, the former would directly influence this bidirectional communication between the brain and the intestine.
Today it is a controversial term since, according to some authors, it should be extended to any intervention that has a psychological effect through changes in the intestinal microbiome, such as sports or diet.
How would these microorganisms send messages to the brain? Three main lines of action are postulated.
1. Through the production of neurotransmitters (or its precursors), which would travel from the intestine to the brain through the vagus nerve. Interestingly, almost half of the dopamine in the human body (known as the pleasure hormone) is produced by the microorganisms that inhabit our intestines.
2. Through the modulation of the main neuroendocrine response system to stress: the hypothalamic-pituitary-adrenal axis (HPA). Its dysregulation and inflammation is evident in people with depression, schizophrenia or bipolarity. Chronic stress, for example, activates this axis, and, in the case of prolonged hyperactivity, it could cause brain damage due to chronic inflammation. Psychobiotics, through mediators and the reinforcement of the intestinal barrier, would help attenuate the HPA and reduce neuroinflammation. Studies in chronically stressed mice confirm this hypothesis.
3. Finally, psychobiotics could interact directly with our immune system, producing short-chain fatty acids. These compounds regulate the function of brain sentinels (microglia), which act against infections and damage to nervous tissue. However, its dysfunction due to chronic stress, diet or inadequate sleep can trigger neuroinflammation, increasing susceptibility to future neurodegenerative diseases.
And to what extent are they effective?
Well, it depends on which one we choose and the problem to be treated. It would be a mistake to think that if I take any psychobiotic it will help me reduce stress, sleep better or improve my mood.
Each psychobiotic (just like a probiotic) has a name and surname that give it specific characteristics, a code of numbers and letters (which we call a strain) that differentiates it from other organisms belonging to the same species.
To make a simile, all dogs belong to the same species (canis familiaris), but there are multiple races (strains in our case) with very different characteristics.
Therefore, it is not surprising that we find in the scientific literature conflicting results regarding the efficacy of psychobiotics in clinical studies.
The psychobiotic strains most related to mental health are those belonging to the genus lactobacillus, Bifidobacterium, Lactococcus Y Streptococcus. Its use has shown, in general, satisfactory results in anxiety, sleep quality, stress and depression.
However, recent reviews and meta-analyses have shown that its effects are more noticeable the higher the level of anxiety or depression initially. In fact, several studies show that certain strains do not produce effects when administered to a healthy population.
It is also important to note that it is wrong to associate greater efficacy with taking a larger number or a wide combination of strains. This not only happens in pathologies such as anxiety or depression, but has also been seen in others as different as atopic dermatitis, irritable bowel syndrome or necrotizing enterocolitis.
For this reason, the choice of a probiotic or psychobiotic should be based mainly on its clinical evidence rather than on the product load that they offer us.
What does the future hold for us in the field of psychobiotics?
Fortunately, we are beginning to elucidate the mechanism of action of psychobiotics.
Studies on its clinical efficacy are already beginning to analyze the reason for its effect and its relationship with the gut-brain axis.
We are experiencing a boom in this field and as consumers we are actively looking for natural alternatives to maintain our mental health, especially after the emotional and behavioral disorders caused by covid-19.
The search on the internet for probiotics that can improve anxiety and stress has skyrocketed in recent years, but we must be cautious. These products can help but never replace a healthy lifestyle or control by a health professional.
As we have previously mentioned, the effectiveness of psychobiotics depends on their characteristics, and these must be tested in clinical studies. Only in this way will we be able to affirm whether or not they have a significant effect on certain populations and understand their mechanism of action.