A mere 22 years ago, in 2002, J. Gruenwald, a Dutch pathologist and entrepreneur, completed a six-month study of 42 adult men and women suffering from stress or exhaustion. Each participant took a newly developed probiotic multivitamin preparation which included L. acidophius, B. bifidum and B. longum, all good bacteria that normally live in our intestines, each day with breakfast.
The study found an overall 41 percent reduction in stress, including decreases of 29 percent in the frequency of infections and 91 percent in gastrointestinal discomforts. Gruenwald concluded that his probiotic preparation reduced stress and exhaustion and improved immune system function, and that our gut biome talked to our brain and immune system about matters other than food, and they listened.
There is no longer any doubt that our gut, frequently referred to as our second brain, connects directly to our first brain via two-way communication. Additional understanding of our microbiome and this “gut-brain axis” is changing medical practices. How the brain and gut converse, the secrets that they exchange, why it’s increasingly important to us, and how we can influence their relationship to improve both our mental and physical health are the topics of this week’s column.
How the brain and gut converse
The sum of our gut, all the microscopic life in our bodies, includes trillions of microorganisms (microbes) combining thousands of different microbiotic species. Bacteria, viruses, parasites, fungi and electrons are all components of our gut microbiome, which is primarily located in our small and large intestines, or digestive tract, although smaller numbers of microbes do spread throughout our body. Everything we do influences our microbiome—where we live and breathe, who and what we touch, what we eat and drink—making everyone’s microbiome unique.
As we learn about our microbiome and its importance to the smooth functioning of our body, medical literature is beginning to refer to this second brain as a supporting organ. It’s that important.
If we’re healthy, there is a symbiotic relationship between these microbes and our body. Infectious illnesses, age, overuse of antibiotics, certain diets and bacteria-destroying medications can disrupt this balance and make us more prone to disease. Hence the importance of our microbiome reporting to mission control, our first brain, when we’re messing up.
One way the brain and gut communicate is via the vagus nerve, a pathway of neurons connecting the base of our brain to our gut. It is the longest cranial nerve in our body. The 100 million nerve cells lining our digestive system comprise the enteric nervous system. To put this in perspective, that’s more nerve cells than are found in the spinal cord.
It gets better. This mass of neural tissue is responsible for producing at least 30 unique neurotransmitters, which are signaling molecules used to ‘converse’ with the brain. Considering that up to 95 percent of serotonin, one example of a signaling molecule related to happiness, is produced in the gut biome, the importance of our gut health to our mental health becomes clear.
The gut microbes that live in the mucous layer of our intestines are in direct contact with our immune cells, a hugely significant information gathering system within our body. It has been confirmed that more than 80 percent of the neurons in these communication paths are signaling from the biome to the brain rather than the reverse, clearly indicating the gut biome’s significant influence on our brain health.
The secrets they share, and don’t
Our brains and microbiome talk about food a lot. Hunger, satiety, preferences and cravings, metabolism, and immunity are all in the discussion. As humans, we need the correct nutrients in the correct amounts. If we’re missing anything in our diet, a properly functioning gut biome will signal the deficiency to our brain. It will raise the alarm via our immune system when we ingest something harmful too, but we don’t always listen.
Medical science is learning that our brain and gut are big emotional partners too. For decades medical specialists believed mental anxiety and depression could trigger stomach upset, bloating, bowel function problems and pain. Researchers now have evidence that communication flows in the other direction too, that gut biome irritations may cause mood changes in the brain.
Seventy percent of our immune cells live in our digestive tract, so microbial disruption frequently triggers an immune response. The resultant inflammation appears as a chronic symptom in many neurological conditions.
Although our enteric nervous system is a team player, it can make its own calls as well. The microbiome system can process the information that it gathers from our gastrointestinal system locally and generate a response without communicating with the brain. The vagus nerve understands these reflexes are intrinsic to the enteric nervous system and don’t need to be passed on. Extrinsic reflexes, those in which all hands on deck are required, get sent immediately to the brain.
Why this gut-brain axis is becoming so important
The following paragraph from a paper authored by Heather Gerrie, BSc, MSc Neuroscience, and published by the University of British Columbia’s Faculty of Medicine, sums up the huge importance of research into what our gut microbiome may be able to tell us, or more importantly project, about our physical and mental health.
“Recent research on Parkinson’s disease found that the enteric nervous system begins to degenerate before the classic symptoms of Parkinson’s appear, and a dysfunctional gut microbiome is typical of this disease. Further, there is a significant decrease in the quantity of microbes in the gut microbiome of individuals with Alzheimer’s disease, with an unhealthy diet being a commonly cited risk factor for Alzheimer’s.”
Co-occurrences like these, where problems in our gut biome foreshadow approaching mental problems, and how this might help our future diagnosis and treatment of many diseases and conditions, are dependent on understanding our gut- brain relationship. Dysbiosis (an imbalance in natural gut microbes) and increases in intestinal permeability are now recognized features presenting with rheumatoid arthritis, asthma, autism spectrum disorders and other systemic conditions, including inflammation.
What can we do to help our gut influence our brain positively?
“We are what we eat,” is true by degree, but there’s more to it than just that.
As we get older, the volume and diversity of microbes in our gut decreases. We also know that imbalance in microbe populations can create problems, and research now suggests that over time we can inadvertently teach our gut to crave too much of certain harmful microbes such as sugar.
Every microbiome is different, meaning that without a gut microbiome test, which are now available in Canada, one is guessing at where deficiencies might lie. However, there are some basic things we know. Soluble and insoluble fibre (fruits, beans, avocados, nuts, etc.) is a primary food source for microbes. Health Canada recommends adult women consume 25 grams of fibre per day, and men 38. Because of the paucity of fibre in processed foods, Canadians consume less than half that on average. As the brain-gut connection is becoming better understood, scientists now say we need 50 grams. Worse still, if our microbes don’t get enough fibre, they will eat the naturally occurring mucous in our gut lining instead, making it porous and allowing various toxins and bad microbes we’ve ingested to cross over into our blood.
Fermented foods are high in probiotics (live bacteria), so a diet diverse in fermented foods and other probiotics is good.
Anti-inflammatory foods keep our gut microbes happy, so whole-food, plant rich diets which reduce sugars, additives and LDL (bad) cholesterol work.
Thank you, medical science. Understanding the gut-brain connection, and how important our gut biome is for our physical and mental health, seems easy to digest. In many cases, correcting poor gut health is not complicated or expensive to implement.
“You can’t change your genes, but all of us have the ability to change our own microbes through simple changes to our diet and lifestyle,” says Tim Spector, an MD and genetic epidemiologist from King’s College, London.
If you’d like more information on the gut biome and its importance, “Hack Your Health: the Secrets of Your Gut,” is a new Netflix documentary that’s not terribly technical and explains gut health and how we influence it for better or worse in a fun and entertaining manner.
