Gut Instinct


By Richard Sutton

The father of modern medicine, Hippocrates, once said, “All disease begins in the gut.” Clinical and research-based evidence strongly supporting this wisdom is accumulating. To fully appreciate the digestive system’s role in health and wellbeing, it is valuable to understand a little more about its anatomy and physiology. The gut spans 9 meters in length in most adults and is our single largest body surface, measuring 200m2. Within its walls there are thousands of specialised cells called ‘enteroendocrine cells’ that secrete 20 different hormones. These hormones constitute one-third of the total hormones produced by the body.

In addition to its hormone-producing cells, the gut contains between 200-600 million neurons (nerve cells), which is why scientists often refer to it as the ‘enteric nervous system’ or the body’s ‘second brain’. According to developmental biologists, both your gut and your brain develop from the same cluster of embryonic tissue (known as the neural crest) during early foetal development, which makes sense when considering the many similarities between the two. Both the brain and the gut have strong protective barriers. The ‘blood brain barrier’ protects the brain from pathogens and toxins in the blood stream while the ‘gut-immune barrier’ acts as a defensive barrier against toxins and pathogens ingested with food. Another commonality of these two systems is that they each require over 40 different types of neurotransmitters (chemicals that carry signals from one nerve cell to another) in order to function, compared with other nerves in the body requiring only 2.

The importance of the second brain and our gut’s role in our overall functionality cannot be understated. According to Dr. Emeran Mayer, a prominent neuroscientist based at UCLA, there is constant bidirectional communication between the gut and the brain. Interestingly, 90% of the communication is from the gut to the brain, implying strong associations in brain functionality. The digestive tract is, for the most part, autonomous, requiring little input from the brain.

Another important role of the gut in human health is that of immunity. In a 2008 European study entitled ‘Allergy and the Gastrointestinal System’, researchers point out that 70% of the body’s immune system is represented in the gut and 80% of the cells that secrete antibodies (proteins that are used to identify and neutralise harmful organisms such as bacteria and viruses) are also found in the gut.

The digestive system also plays a role in the production of molecules and proteins that facilitate brain functioning. According to Dr. Pankaj Pasricha, Director of the Johns Hopkins Center for Neurogastroenterology, over 90% of the body’s serotonin and over 50% of the body’s dopamine is found in the gut. Serotonin and dopamine are neurotransmitters that influence mood, memory, learning, attention, focus, sleep, movement, as well as the cardiovascular, nervous, and skeletal systems. Our entire cognitive, emotional, and physical well-being is dependent on dopamine and serotonin and the digestive tract is the primary engine in the supply chain. One would assume that, in light of the important roles of dopamine and serotonin in our functioning, the body would have strict control measures over their production and regulation. However, in a bizarre twist, a team of researchers from the California Institute of Technology have discovered that serotonin levels are not regulated by the body itself, but rather by bacterial colonies residing in our gut!

Jessica Yano and her team found that levels of serotonin in the blood were influenced by intestinal flora (the microbiome) to such an extent that disrupted bacterial profiles could lower serotonin production by up to 60%. The study suggests that by promoting optimal bacterial balance in the gut, we could improve symptoms of serotonin-related diseases like obsessive-compulsive disorders, depression, and anxiety. The human body has been a host to resident bacteria for thousands of years. There are around 10 000 different species occupying the human habitat with 1000 different species found in the gut, of which 90% offer functional value. These colonisers are so numerous that they outnumber our own body’s cells by 10-1 and represent 3% of our total body weight.

The microbiome is an integral part of many biological systems. For example, it regulates our immune system by promoting the development and maturation of our immune cells. It also creates an actual physical barrier in our gut, protecting us against dangerous organisms like harmful bacteria, viruses, and parasites. It even acts as a detoxification system in much the same way as the liver. In addition, it is well established that the microbiome is responsible for the production of the essential vitamins B and K, but what has recently been discovered is its role in the production of important molecules (over and above serotonin) that are essential to brain health and function.

In a 2014 article that was published in the journal ‘Frontiers in Neuroscience’, the connection was made between the microbiome and the production of Gamma-amino Butyric Acid (GABA), which is an important protein known for its role in calming the brain and nervous system. Multiple studies also show the microbiome’s influence in the production of Brain Derived Neurotropic Factor (BDNF), a powerful brain chemical responsible for many aspects of brain cell development.

The pattern that is emerging is one where the gut and microbiome are an integral part of three major bodily systems: nervous, immune, and hormonal – and as such, any compromise to integrity and functionality has far reaching consequences.

According to world-renowned neurologist, Dr. David Perlmutter, many of the following ailments can directly be attributed to gut and microbiome dysfunction:

  • Memory and concentration issues
  • Chronic fatigue
  • Asthma, allergies, and food sensitivities
  • Mood disorders (depression and anxiety)
  • Obesity and weight issues
  • Digestive issues/disorders
  • Diabetes, sugar, and carbohydrate cravings
  • Insomnia
  • Frequent colds and infection
  • Joint pain and inflammation
  • High blood pressure
  • Atherosclerosis

Microbiome dysfunction is becoming more common for a variety of reasons, but according to Perlmutter the major reasons include:

  • Antibiotics (at least once every 2-3 years)
  • Medications containing cortisone
  • Having an appendectomy
  • Birth by C-section
  • Not being breast fed as a baby

Although some of these risk factors may be beyond our control, there are choices we can make, especially in relation to diet, that can further impact this vital ecosystem. A 2012 study by Dr. Kirsty Brown from the Department of Biology at the University of British Columbia published in the journal ‘Nutrients’ showed that dietary patterns account for 60% of the bacterial balance in the gut. For example high fat, sugar, and carbohydrate diets had a detrimental effect on the microbiome in that pathogenic bacterial species thrived and the populations of bacteria that conferred benefit declined. The study also showed that diets high in fiber, protein, omega 3 fatty acids, and complex unrefined carbohydrates created optimal microbial balance.

There are many things we can actively do to promote microbiome integrity and consequently proper gut health, here is a breakdown:

Try to avoid:

  • Unnecessary antibiotics
  • Excessive consumption of foods exposed to antibiotics (meat, poultry, dairy)
  • Processed sugar
  • Saturated and trans fats
  • Emulsifiers (found in processed foods)
  • Artificial sweeteners
  • Gluten (wheat, barley, rye, spelt, and oats)
  • Pesticides and herbicides (in particular Glyphosate)
  • Tap water (due to high chlorine content)

Try to incorporate:

  • Daily probiotics (bacteria that benefit our health) – taken in supplement form or obtained through foods that are prepared by bacterial fermentation (eg. yogurt, kefir). Different strains of probiotic bacteria have slightly different functions and, accordingly, supplements that contain multiple strains tend to be more effective overall as opposed to products containing high concentrations of just one or two strains.
  • Consume prebiotics (compounds that good gut bacteria eat to fuel their growth and activity) – found in many fruits and vegetables, foods high in prebiotics include beetroot, artichokes, asparagus, leeks, garlic, apples, bananas, dates, and cashews. 100 grams of prebiotics is typically associated with the production of 30 grams of good bacteria.

It is strongly recommended that you consult with your doctor before starting any new diet plan, especially if you have existing health issues.

Visit for more details.

Related posts