Updated: 15/12/2023 por Jennifer Delgado | Published: 28/05/2018
Can you imagine that you feel depressed, stressed or anxious and, instead of prescribing psychotropic drugs, the psychiatrist recommends an abundant dose of sauerkraut, kimchi or yogurt? It is not a fantasy, psychobiotics are becoming the new promise in the field of Neurosciences and are as promising as in the 1960s were the drugs synthesized in the laboratory. And the key is in the enteric nervous system, our second brain.
What are psychobiotics?
Fermented foods and beverages, rich in probiotics, have a long history, they are not a modern discovery. In fact, their origins are lost in the annals of time as it is known that Neolithic men fermented intentionally fruits, rice and drinks with honey. It is believed that kefir was an invention of the shepherds of the mountains of the North Caucasus, dating from 8000 a.C., who discovered that fermented milk could be better stored. Also, it is believed that sauerkraut was an idea of Mongols, 2,000 years ago in China, and later was introduced in Europe.
However, beyond the potential of preservation of fermented foods, we now know that products with probiotics are beneficial for health. In practice, the fermentation increases the bioavailability of nutrients; in other words: fermented foods contain beneficial bacteria, which are known as probiotics. These facilitate digestion and, of course, contribute to the development of a healthy intestinal flora.
Thanks to the latest research on the human microbiome, we now know that these bacteria can also influence our mood, decisions and behaviors. That is why Ted Dinan, a psychiatrist at the University of Cork, coined the term psychobiotics.
What are psychobiotics? These are living organisms that, when ingested in the right quantities, produce a benefit for mental health. Unlike probiotics, psychobiotics contain other strains of bacteria that have the ability to modulate the function of the adrenal cortex, which is responsible for controlling anxiety and the response to stress, as it is where is produced approximately 95% of the cortisol that makes our body.
However, before understanding how psychobiotics work, it is necessary to understand the mechanism of the enteric nervous system, considered our second brain.
The enteric nervous system: How does our second brain work?
Different neuroscientists from around the world have been analyzing our intestinal system from a different perspective for several decades, to the point of considering it our second brain.
It has been discovered that our intestinal system has about 100 million neurons, much more than those found in the spinal cord and the entire peripheral nervous system. These neurons not only allow us to “feel” our inner world being responsible for sensations that we describe as “butterflies fluttering in the stomach” or “a knot in the stomach”, but also give some independence to the enteric nervous system from the brain.
What surprised most neuroscientists is that more than 30 neurotransmitters, the substances that neurons normally use to communicate, are produced in the enteric nervous system. In fact, they have discovered that 95% of the body’s serotonin, which is related to pleasure and tranquility, is found in the intestines.
The enteric nervous system would be “connected” to the brain through the vagus nerve, which is primarily responsible for carrying information from the intestine to the brain. Interestingly, the bacteria that inhabit the intestine are also actively involved in the production of these neurotransmitters.
Psychobiotics have the ability to generate many neurotransmitters and neuromodulators that are found in the brain, such as GABA, norepinephrine, serotonin, dopamine and acetylcholine. Through the gut-brain axis, a complex bi-directional communication network composed of the autonomic and enteric nervous system, the neuroendocrine system, the metabolic system and the immune system; these neurotransmitters end up influencing our mood, decisions and behaviors.
Therefore, the dysfunction in the bowel-brain axis is related to mental illnesses such as anxiety, depression, autism, schizophrenia and some neurodegenerative disorders. This discovery acquires a particular relevance at present, mainly due to the abuse of antibiotics and medicines, as well as the consumption of foods with artificial preservatives and traces of herbicides, which affect the balance of the intestinal microbiome.
In fact, some neuroscientist have even postulated that the epidemic levels of anxiety and depression that we are experiencing nowadays are not only explained by the modern lifestyle, but also would be caused by an inadequate diet that affects the bacteria responsible for producing some basic neurotransmitters to improve our mood and the functioning of our cognitive functions.
The benefits of psychobiotics for mental health
Both animal experiments and studies with humans have reached the same conclusions: psychobiotic foods are beneficial for our mood and cognitive functions.
How can psychobiotics help us?
– Decrease emotional reactivity. Neuroscientists at UCLA asked a group of people to consume yogurt rich in psychobiotics twice a day for four weeks. When subjected to brain scans, they discovered that these persons had a decreased activity in the areas of the brain related to sensations and emotions, which means that they were able to control better their emotional responses to the stimuli and that they did not react with excessive stress.
– Improve cognitive functions. In that same study, neuroscientists appreciated that participants who consumed psychobiotic foods had a greater connectivity between the brainstem and the prefrontal cortex, the area of the brain associated with cognition and decision making. That connectivity would facilitate communication with the spinal cord and peripheral nerves.
– Decrease stress and anxiety levels. Japanese neuroscientists asked a group of medical students who were preparing for a major exam, to drink fermented milk for eight weeks. When compared with the group that followed their usual diet, they discovered that those who had consumed psychobiotics showed lower levels of cortisol, a marker of stress, as well as higher levels of serotonin, which enhances a sense of well-being. In addition, they reported fewer gastrointestinal symptoms related to stress and anxiety.
– Improve the mood. A study conducted by Iranian researchers found that people who followed a diet with psychobiotic foods, showed a significant improvement in their mood. After eight weeks, they also showed significantly higher levels of glutathione, an amino acid that helps prevent depression.
– Fight anxiety and obsessions. It has been discovered that psychobiotic foods containing Lactobacillus rhamnosus, a bacterium found in the human intestine, can reduce anxiety because it changes the expression of GABA receptors, the main inhibitory and relaxing neurotransmitter in the central nervous system. And if this is not enough, a study developed at Lehigh University found that, at least in animals, this bacterium is as effective in treating obsessive-compulsive disorder as fluoxetine.
– Reduce depression. A meta-analysis by Chinese neuroscientists found that psychobiotic foods can relieve the symptoms of major depression in people under 65. They considered that the consumption of Bifidobacterium infantis or Lactobacillus rhamnosus during just 6 weeks, was sufficient to produce a significant improvement, and they proved that these bacteria changed effectively the brain biochemistry, decreasing also the level of psychological distress and stress.
Obviously, this does not mean that psychobiotic foods are the magic response to cure mental illnesses, but it is a new line of research that could work in people who do not respond to conventional medication or in which psychotropic drugs cause many adverse effects. For now, we should worry a little more about feeding our second brain correctly.
Sources:
Kato-Kataoka, A. et. Al. (2016) Fermented milk containing Lactobacillus casei strain Shirota preserves the diversity of the gut microbiota and relieves abdominal dysfunction in healthy medical students exposed to academic stress. Applied and Environmental Microbiology; 82(12):3649-3658.
Akkasheh, G. et. Al. (2016) Clinical and metabolic response to probiotic administration in patients with major depressive disorder: A randomized, double-blind, placebo-controlled trial. Nutrition; 32(3): 315-320.
Huang, R. et. Al. (2016) Effect of Probiotics on Depression: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients; 8(8): 483.
Dinan, Timothy G. et al. (2015) Collective unconscious: How gut microbes shape human behavior. Journal of Psychiatric Research; 63: 1-9.Kantak, P.A. et. Al. (2014) Obsessive-compulsive-like behaviors in house mice are attenuated by a probiotic (Lactobacillus rhamnosus GG). Behav Pharmacol;25(1): 71-79.
Tillisch, K. et. Al. (2013) Consumption of Fermented Milk Product With Probiotic Modulates Brain Activity. Gastroenterology; 144(7).
