A field of medicine known as psychobiotics is emerging.
Recent advances have shown that the gut microbiota (the collective name for the bacteria that lives in the digestive/intestinal tract) and its interaction with the brain, influences behavior and mental health. This acknowledged interaction has attracted the attention of neuroscientists and psychiatrists as a potential therapy for the problems of various mental health disorders.1
In a new study from the Ruđer Bošković Institute in Croatia, (a leading institute for this microbotica research) doctors note the proven existence of bidirectional communication between the brain and the gut and the increasing body of evidence which supports the hypothesis that cognitive and emotional processes are influenced through the brain-gut axis.2
In simple terms the gut and brain talk to each other. What do they talk about? Digestion, inflammation and diet.
My Gut tells me – Digestion, Inflammation and Mental Health
Old idioms reveal and amazing knowledge of the human body our ancestors had. They knew that the gut talks. “My gut tells me…”, “My gut reaction…”, “My gut thinking on this … ”
In November 2016, doctors at Oxford University and their colleagues at other universities released a study entitled: Psychobiotics and the Manipulation of Bacteria–Gut–Brain Signals.
Here is a summary of their fascinating findings on how the gut and brain talk to each other.
Better mood through communication
Gut bacteria produce a range of neurotransmitters through the metabolism of indigestible fibers. These include the following with a very simple and general explanation of its influence
- dopamine (reward and pleasure)
- noradrenalin (alertness and sexual arousal)
- GABA Gamma-Aminobutyric acid (low levels linked to anxiety and issues of chronic pain)
- serotonin (low levels implicated in depression)
- acetylcholine (reward and arousal)
The gut produces the neurotransmitters, the neurotransmitters talk to the brain.
Anti-Inflammatory effect through metabolism of Short chain fatty acids (SCFAs).
The gut talks to the brain through the metabolization of dietary fiber which produces short-chain fatty acids (SCFAs). These include acetate, butyrate, lactate, and propionate. SCFAs have been shown to reduce low-grade inflammation. It is suggested that inflammation plays a role in depression. Equally high fat diets have been shown to stimulate SCFA acetate’s role in triggering the likelihood of obesity and inflammation.
The gut produces short-chain fatty acids, the short-chain fatty acids either reduce inflammation and has a positive effect on depression – such as on a high fiber diet – or short-chain fatty acids increases inflammation and its negative effects on depression – such as on a high fat diet.
Anti-inflammatory effect – regulation pro-inflammatory cytokine concentrations
It is suggested that pro-inflammatory cytokine concentrations (the inflammation that makes a disease worse) are capable of increasing the permeability of the blood–brain barrier permitting access to the potentially physically and mentally pathogenic entities. In simplistic terms – the makers of bad thoughts because they can alter and lower levels of serotonin, dopamine, and glutamate (an amino acid involved in mental health).
- Strains of probiotics Bifidobacterium and Lactobacillus have been shown to help reduce the total quantity of pro-inflammatory cytokines, either directly or by increasing anti-inflammatory cytokines.3
As these researchers point out, there are many complexities to this relationship between the gut and the brain. One of the complexities is the role of obesity.
The chemical role of obesity on mental health
Doctors at Eastern Washington University and Dartmouth College have released a study that ties obesity and an altered gut environment with compromised brain function, leading to the development of mental illness.
The doctors noted that the gut microbiota, and changes associated with diet, affect the gut-brain axis and may possibly contribute to the development of mental illness.4
This study connects obesity and altered gut environment as a possible cause of impacted brain function and mental illness. Now researchers say the drugs prescribed to fight mental illness cause obesity and altered gut and brain function.
Drugs for mental illness lead to obesity, obesity leads to mental illness
Researchers at the University of Iowa have shown that drug-induced changes to the gut microbiome can cause obesity by reducing the resting metabolic rate – the calories burned while sleeping or resting.
The findings, published in the journal eBiomedicine highlight the critical role of gut microbes in energy balance and suggest that unhealthy microbiome shifts can lead to weight gain and obesity by altering resting metabolism.
The link between the gut microbiome and obesity seems clear, but just how changes to gut bacteria can cause weight gain is not.
The researchers focused on the effects of risperidone, an antipsychotic drug that causes significant weight gain in patients.
Risperidone is used to treat various psychiatric disorders in adults and children including:
- bipolar disorder, and
- and prescribing rates for children have increased nearly eight-fold over the last two decades.
In an earlier study, the same researchers compared patients taking risperidone long-term to patients who were not on the drug. They found that weight gain was correlated with a significant shift in the composition of the patients’ gut microbiomes
The results may suggest that manipulating resting metabolic rate, specifically by targeting the gut microbiome, could represent a new approach to treating obesity.5
Recently a team of researchers from Vanderbilt University presented their findings that friendly bacteria produce a therapeutic compound in the gut which inhibits weight gain, insulin resistance and other adverse effects of a high-fat diet in mice and that it may be possible to manipulate the bacterial residents of the gut – the gut microbiota — to treat obesity and other chronic diseases.6
In recent research, doctors also found that certain probiotics could help women lose weight and keep it off. Women consuming probiotics lost twice as much weight over the 24-week period of the study.7
In a report from earlier this year (2016) doctors recognize the difficulty in managing what they call a “healthy microbiota” and suggest to clinicians the following beneficial aspects can be found in patients despite age:
- Reductions in weight gain and, in particular, fat tissue mass at different locations
- Anti-inflammatory effects-including regulation of expression of lipogenic and lipolytic genes in the liver, (cholesterol)
- Reduction in liver steatosis (fatty liver),
- Improvement of blood lipid profile and glucose tolerance,
- Decreased endotoxemia (blood toxins)
Do you have questions about obesity, the gut and mental illness
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1. Foster JA, Lyte M, Meyer E, Cryan JF. Gut microbiota and brain function: An evolving field in neuroscience. Int J Neuropsychopharmacol. 2015 Oct 4. pii: pyv114. doi: 10.1093/ijnp/pyv114. [Epub ahead of print]
2. Vlainić J, Šuran J, Vlainić T, Vukorep AL. Probiotics as an adjuvant therapy in major depressive disorder. Curr Neuropharmacol. 2016 May 26. [Epub ahead of print]
3 Sarkar A, Lehto SM, Harty S, Dinan TG, Cryan JF, Burnet PWJ. Psychobiotics and the Manipulation of Bacteria–Gut–Brain Signals. Trends in Neurosciences. 2016;39(11):763-781. doi:10.1016/j.tins.2016.09.002.
4 Ochoa-Repáraz J, Kasper LH. The Second Brain: Is the Gut Microbiota a Link Between Obesity and Central Nervous System Disorders? Curr Obes Rep. 2016 Mar;5(1):51-64.
6. Certain probiotics could help women lose weight. January 28, 2014
7. Yu RQ, Yuan JL, Ma LY, Qin QX, Wu XY. Probiotics improve obesity-associated dyslipidemia and insulin resistance in high-fat diet-fed rats. Zhongguo Dang Dai Er Ke Za Zhi. 2013 Dec;15(12):1123-7.