The stomach is often referred to as the second brain due to the fact that it is the largest endocrine organ, the main storage site for serotonin (a brain modulating hormone) and has a very intricate nervous system.
Technically however, it is actually the first brain and this connection goes back to beginning of life on earth…The first organisms on the planet were much simpler structured organisms such as algaes and microbes. They were basically floating digestive tracts surrounded by dense nervous systems. When these organisms evolved they gained other organ systems and eventually developed brains and now these structures can be found in virtually every life form on earth from fleas to elephants. So the fact that the gut has an effect on the brain and vice versa is very understandable when seen under the light of evolution. The bidirectional signalling and connection between the gut and brain is strongly established and the gut/ brain connection is now known for having major homeostatic governance in the body. It’s well-known now that the gut is more than a digestive space, it’s also the largest sensory organ, comprised of more than 100 million nerve cells, and the largest producer of serotonin in the body.
Research is now looking into the influence microbiome within the gut has on the this gut/ brain communication. While this research is still in its infancy there have been some interesting clinical studies that have demonstrated the beneficial effect of probiotic supplementation on the reduction in the reccurence of mania in patients admitted to hospital with psychiatric disorders. And similar studies are underway on bipolar patients in regards to treating their depressive state as well.
The gut is filled with millions of microbes that produce substances which communicate with the brain and the immune system, and are thought to play a role in how we feel mentally. “Certain gut microbes stimulate the production of serotonin in the gut, which ultimately impacts levels in the bloodstream and in the brain,” explains Emeran Mayer M.D Author of TheMind/Gut Connection and gastroenterologist at UCLA. In addition he says that “others produce gamma-aminobutryic acid, another neurotransmitter whose effects are mimicked by medications such as Xanax and Valium. If we’re low on these critical microbes or they are not communicating properly, it can ultimately lead to disturbances in the brain, and therefore mood.”
Meyer says when patients come to him with issues such as irritable bowel syndrome, acid reflux, and ulcers. Many are also dealing with anxiety, panic disorder, and depression, and he is convinced there is a connection. “Every emotion in the brain is felt in the gut, and every gut disturbance is felt in the brain—they are truly inseparable,” he says.
One way to understand how the gut affects our state of mind is to look at the effects of chronic stress on digestion and how this in turn can effect microbial balance within the digestive tract, which in turn creates psychological disturbances that can exacerbate the triggers for chronic stress. Stress causes changes in multiple gut functions by triggering the flight or fight response. Managing negative emotions plays a role too. “Chronically being angry, upset, fearful, or sad sends a message to your gut and from your gut back to the brain and negatively impacts the microbes,” Mayer says.
When the body is in a state of alarm and negativity it shifts its priorities from everyday functions such as digestion (and immune activation) and sends extra energy and blood flow to the parts of the body that will help it evade the threat of imminent danger such as the muscles and adrenal glands. This results in a decrease in contractions in the digestive tract which in turn increases the transit times of foods through the gut and decreases the secretion of digestive fluids.
If this response is a short lived event then the body will readjust fairly quickly when the threat has gone away. However, when the stress becomes chronic these changes become detrimental. The prolonged changes in the digestive environment makes it difficult for the beneficial microbiome to flourish and this can then result in gut issues that can eventually cause behavioural complaints. Chronic stress can also increases the likelihood of a weakening in the gut lining which is commonly known as leaky gut. This leads to larger food particles being allowed through the gut lining and into the blood stream which can cause immune responses that can also result in behavioural problems. Joseph Hibbeln, the acting chief of nutritional neurosciences at the National Institutes of Health. says “We think that some people with depression have low-grade persistent inflammation that arises when the immune system activates a type of cell called the microglia in the brain,” explains Hibbeln. “When those cells are turned on, they set off an entire inflammatory cascade that restricts the release of dopamine, a neurotransmitter that regulates emotional responses.”
Antibiotics are powerful drugs that have helped reduce the prevalence of diseases caused by bacteria worldwide. When used appropriately, they quickly and effectively eliminate infections. However according to Dr. Martin Blaser best selling author of Missing Microbes and preeminent authority on the negative impact of antibiotic use on the gut microbiome, the growing prevalence of chronic diseases such as obesity and chronic gut inflammation may be linked to the excessive use of antibiotics when they are not necessary. Dr Blaser cites some interesting statistics on antibiotic use :