The human body consists of approximately 30 trillion cells. There are approximately 40 trillion bacteria in our intestines. It is for this fact that it could be said we are more bacteria than man.
Bacteria predates man by billion of years and will likely out survive our species by billions more. These single-celled lifeforms are really the very basis of all life. They reside in every living being on earth including the human body. Primarily in our gut, bacteria provides protection from pathogens to ensure our survival by a day to day battle against other harmful bacteria and to allow healthy gut bacteria to flourish.
It is estimated that out of the 40 trillion bacteria found in the intestines, there are 30-40 species on average with a total of 1,000 different species in all. This group of bacteria is known as the microbiome. Most of the single-celled substances reside in the colon.
Bacteria seem to thrive in a warm and nutritious setting, like the colon. There they can do the job of breaking down fiber into short-chained fatty acids so we can enjoy the benefits by absorbing and utilizing the compounds. They also help to synthesis vitamins K and B as well as play an important role in downplaying inflammation and autoimmune conditions.
The Link of Gut and Brain
The link of the gut to the brain is a two way street. It has a neural, hormonal and immunological nature that involves the central nervous and the enteric nervous systems (controls gut function). This entire process is referred to as the gut-brain axis.
For many years researchers have curiously studied the unique relationship of our gut health to our mental health. It is only until recently they have been closer to connecting the dots into what they now term, the microbiome-gut-brain axis. According to data collected from the conversations our guts have with our brain, scientists have witnessed how anxiety and stress diminishes the capability of this system to exchange its vital information.
Stress and Gut Health
The brains response to stress directly impacts the guts response from the epithelial and interstitial cells to the immune and enterochromaffin cells (synthesis of serotonin).
One of the primary responders to stress involves the limbic system (emotions and memory center), which is part of the hypothalamic-pituitary axis (HPA). The HPA releases the stress hormone cortisol when it is activated by stress. This action can have damaging affects on many organs throughout the body including the gut and brain.
Although, the findings are in the beginning stages it does appear to indicate a back and forth of communication from gut to brain and back.
Microbes and Mental Health Conditions
Throughout the years there has been mounting clues left to indicate how our mental health is affected by changes in gut diversity.
One of the first clues came over 20 years ago when medical professionals could see how patients with hepatic encephalopathy or (a decline in neural functioning due to liver disease) was improved with oral antibiotics.
Research from 2004 demonstrated in studies with mice, that those who are void of gut bacteria have an extreme HPA axis reaction to stress and after more study appear that a more pristine and less diverse microbiome changed memory function.
The history of microbiome-gut-brain axis studies have either been attempting to answer the old chicken to egg question, by looking at the psychoneurological condition impacted by the gut flora or the other way around. The prevailing science has seen enough data that would indicate the establishment to dig deeper into what could reveal a two-way interaction of behaviors to gut flora.
For instance, hints that anxiety and depressive like behaviors are impacted by microbiome was found in later studies. Along with the fact that children with autism have abnormal and less diverse gut bacteria or dysbiosis (gut imbalances).
Some researchers have concluded that certain gut microbes can alter the gut-brain axis communication networks thus affecting brain function. Gaining a better understanding of neurotransmitter-related metabolite levels are key to opening the door on the communication activity of bacteria and autism.
How to Change Brain Activity with Gut Flora
One way bacteria can alter our brains functioning capability and thus our mental health is through stress. Stress can gain access to our immune system and the neuronal cells of our enteric system through causing greater permeability of the intestinal lining.
More direct ways of changing brain activity, involve food-borne pathogens which have shown evidence of intestinal bacteria activating the vagus nerve (large cranial nerve informational supply to many organs).
Other direct routes on how bacteria can alter our mental state of health comes from having direct contact with sensory neurons of the enteric system from the microbiome. Where studies have shown that after this happens, sensory neurons become less active and only after probiotics were administered, that the activity levels of the sensory neurons resumed to normal.
The germ-free mice studies have been extremely enlightening on demonstrating the impact of gut bacteria diversity has on differences in behaviors.
The quest to determine closer connections to find answers to the gut- brain axis lead to a meta-analysis published in the Journal of Neurogastroenterology and Motility. It looked at the effects of probiotics on the central nervous systems of humans and animals.
The study involved 15 humans and 25 animals over a 2-4 week period of time, where the subjects were given Bifidobacterium and Lactobacillus. It was concluded that:
“ These probiotics showed efficacy in improving psychiatric disorder-related behaviors including anxiety, depression, autism spectrum disorder, obsessive -compulsive disorder, and memory abilities, including spatial and non-spatial memory.”
There was another study that showed by altering levels of Actinobacteria and Bacteroidetes with probiotics in rats, demonstrated to reverse the signs of age-related memory decline in them.
Looking to the Future in Gut-Brain Axis
The idea of looking to the microbiome-gut-brain axis to find remedies for common mental health conditions could seem convoluted and far-reaching. Seeing the many multitudes of microbes that are involved and then determining to what degree they affect neuronal communication and state of mind is a daunting task.
But, the saying “everything starts in the gut” is an old one that’s rooted in truth. Single-celled microbes have been around much longer than humans. They are extremely intelligent in adapting to their environment to survive and are an integral part of the human experience. These single-celled lifeforms are partially responsible for our health. To what degree is the purpose of new research.
The future study of the human microbiome could have immense importance in that it could open a new way to diagnose psychiatric conditions, serve as an early warning signal to disease and offer a brand new approach to treatment.
-A Balanced Brain is a Better Brain-