The Gut is Your "Second Brain"

Get smart – take good care of your ‘second brain’

13 June, 2012
Our bodies have two brains. There’s the one we all know about and a second one – in our guts.
Both of these brains begin to form almost from the moment an egg is fertilised and develop from the same clump of tissue.
As this embryonic tissue divides during fetal development, one section evolves into the central nervous system, another into the enteric nervous system. Later these two nervous systems connect via the vagus nerve – the longest of all the cranial nerves. The vagus nerve stretches from the brain stem through the neck and finally ends up in the abdomen providing continuous two-way line of communication between the gut and the brain.
In the last decade or so scientists have discovered that each brain influences the other and imbalance in one can mean imbalance in the other.
The gut brain
In his ground breaking book The Second Brain, Dr. Michael Gershon, a professor of anatomy and cell biology at Columbia-Presbyterian Medical Center in New York City, says:
“The brain is not the only place in the body that’s full of neurotransmitters,” he says. “A hundred million neurotransmitters line the length of the gut, approximately the same number that is found in the brain…”
Those butterflies in your stomach it turns out are real and caused by a surge of stress hormones released by the body in a “fight or flight” situation.
A little number crunching reveals that the total number of nerve cells in the esophagus, stomach and large intestine, outnumber those in the whole of the peripheral nervous system (that portion of the nervous system that resides outside the brain and spinal column). Nearly every chemical that controls the brain in the head has been identified in the gut brain, including hormones and neurotransmitters (like serotonin).
A double whammy
Thus it is hardly surprising that conventional drugs can deliver a double whammy of effects in the mind and the digestive tract.
Antidepressants can cause gastric distress in up to a quarter of the people who take them. Likewise, stress can also overstimulate nerves in the esophagus, causing a feeling of choking.
In addition:
  • People suffering from  Alzheimer’s and Parkinson’s diseases also suffer from constipation; the nerves in their gut are as sick as the nerve cells in their brains.
  • Autoimmune diseases like Crohn’s disease and ulcerative colitis may also involve the gut’s brain. The consequences can be devastating, as in Chagas disease, which is caused by a parasite found in South America. Those infected develop an autoimmune response which means their immune systems slowly destroy their own gut neurons. When enough neurons die, the intestines literally explode.
  • The gut’s brain and the head’s brain act the same way when they are deprived of input from the outside world. During sleep, the head’s brain produces 90-minute cycles of slow wave sleep punctuated by periods of rapid eye movement sleep in which dreams occur. During the night, when it has no food, the gut’s brain produces 90-minute cycles of slow wave muscle contractions punctuated by short bursts of rapid muscle movements. The two brains may influence each other while in this state. Patients with bowel problems have been shown to have abnormal REM sleep – a finding that may go some way towards explaining how indigestion can cause nightmares.
  • Drugs designed to have psychic effects on the brain, are very likely to have an effect on the gut as well. For instance around a quarter of people taking Prozac or similar antidepressants that alter serotonin levels in the body, can end up with gastrointestinal problems like nausea, diarrhoea and constipation .
With regard to this last point, evidence suggests that IBS originates from a change in serotonin levels. In a healthy person, serotonin in the gut is cleared from the bowel by a serotonin transporter found in the cells that line the gut wall.
In IBS sufferers, this may not be happening and leaving the person with too much serotonin swirling round the system, causing diarrhoea, then overwhelming the receptors, shutting them down and leading to constipation.
A holistic view
The direct links between the brain and the digestive tract are a important model for a holistic thinking about health.  Recent studies suggest that a healthy gut in infancy can, in addition to helping to maintain immunity have a profound effect on our mind and emotional health later in life. Other data suggest the “cross-talk” between bacteria in our gut and our brain plays an important role in the development of psychiatric illness, intestinal diseases and probably other health problems including obesity.
But he opposite is also true. Our psychological, social and environmental environment can influence symptoms like pain and inflammation in the gut as well as how efficient our digestive process is.
Research suggests that some people with functional gastrointestinal tract (GI) disorders perceive pain more acutely than other people do because their brains do not properly regulate pain signals from the GI tract. Stress can make the existing pain seem even worse.
While many people with gut disorders like IBS and Crohn’s would reject the idea of treating the problem psychologically (undoubtedly tired of being told it’s all in their minds!) there is evidence that therapy to reduce stress and anxiety can have a profound effect on gut symptoms.
For instance a review of 17 studies showed that patients who tried psychologically based approaches had greater improvement (up to 50% reduction in symptoms) compared with patients who received other treatments treatment.
Vital for immunity, too
In addition to all this, almost 70% of the immune system is found in the gut. So keeping your gut healthy is doubly important.
To do this requires a balance between the good and bacteria native to the human gut. In a healthy gut, the ‘good’ usually outnumber the bad; and when they flourish they also help:
  • to ferment organic acids into glucose,
  • lower blood cholesterol,
  • synthesise vitamins,
  • break down the enzymes and fibres in food
  •  boost the immune system.
Lack of variety in our diets means lack of variety in our gut bacteria.
All the so called ‘good’ bacteria in the gut need to be fed each day so that organisms that die off or are excreted are replaced regularly.
To do this we ideally need to include around 40g of various hard-to-digest carbohydrates, often referred to as “prebiotics”, in our diet each day. Without their preferred food supply, numbers of beneficial gut bacteria decline rapidly, with a knock on effect on immunity and other bodily functions.
Maintaining that balance from early in life has as much influence on our mental and emotional health as it does our physical health.
Keeping your second brain healthy
Across the developed world we spend billions on pills to treating gastrointestinal disorders. But are we making the job harder and more expensive than it needs to be? Anti-acid medications such as proton pump inhibitors (PPIs) may provide relief in the short term, but over the longer term they suppress the absorption of vitamin B12 and calcium, and are linked to bone and brain shrinkage. Pain-killers such as aspirin and ibuprofen can also damage the gut.
Maintaining a healthy gut is often a matter of common sense for instance
  • When you are eating – eat. Don’t text, talk on the phone or watch TV – and don’t eat when you are stressed as adrenaline can interfere with digestion. Digestion begins in the mouth so take time to really chew your food thoroughly to give your gut a helping hand.
  • Spread your meals out over the day. ‘Grazing’ on five smaller meals a day is easier on your digestion and helps keep your energy up and your blood sugar levels in balance.
  • Don’t skip breakfast. The hint is in the name ‘break fast’. Your morning meal comes after a long period of fasting, when your blood sugar will be at its lowest point. Eat well to ensure plenty of energy to take you to lunchtime and beyond.
  • Cut back on acidic foods like meat, wheat, sugar, fried foods, coffee and alcohol and try to make around 80% of your diet alkalising stomach-friendly foods such as vegetables, fish, pulses and rice.
  • Eat fruit away from main meals, for instance as snacks during the day. A fruit salad after a heavy meal can cause indigestion.
  • Don’t eat too late at night – instead try to eat at least three hours before you go to bed.
  • Use herbs. A number of medicinal herbs such as ginseng, ginkgo biloba, liquorice and chamomile help feed bacteria in the gut. Using herbs and spices such as cumin, cinnamon, coriander, nutmeg, parsley can also help keep unfriendly bacteria populations down, as well as making your food more enjoyable.
  • Boost gut bacteria with healthy probiotics and prebiotics. Live yoghurt, fermented drinks such as kefir should be part of your every day diet. These tend to be rich in probiotics acidophilus and bifido bacteria. Prebiotics are foods that feed and stimulate the growth of healthy bacteria in the gut. Raw oats, unrefined wheat and barley, Jerusalem artichokes, chicory, leeks, garlic onions, asparagus, bananas and dandelion greens are all excellent sources.
  • Deal with food allergies and intolerances. If you suspect you might have an intolerance, consult a nutritionist who can arrange tests for you. You can also try a home test kit, for example from
  • Practice stress reduction. Both yoga and meditation are excellent ways to relax. Regular exercise is also important. But any hobby that absorbs you completely will substantially lower your levels of stress hormones and this will have a knock on effect on gut health. So remember – make space for yourself and the things you enjoy.