The Gut instinct on Gut Health 2/3

Although some people struggle to use one, we talk here about an entirely different brain and nervous system, not located in our head, but more surprisingly through our digestive tract.

The Second Brain

Yes you read it correctly, we have a brain in our gut.  This second brain will not help much with general thought processes like mathematics and philosophy, instead it is responsible for much of the critical complex processes of the gut, and as we discuss below – so much more.

The contribution of this second brain and how it behaves, could be considered as important as the brain inside our head. Our gut brain is now being understood as the control centre for important functions like immune response, hormonal signalling, emotions, metabolism, mood and so much more.
Situated throughout our digestive tract amongst the trillions of the gut microbes we discussed in part one, you’ll find this network of neurons that are revealing a communication process resembling a fully functioning brain. The complex independent network of neurons and it’s relationship with the bacteria inside us all, is only recently being understood and this article will help you understand what they know so far.


As mentioned, our body has a separate neural network known as the Enteric Nervous System or (ENS), located within sheaths of tissue lining the oesophagus, stomach, small intestine and colon. This nervous system comprises an estimated 500 million neurons (the average cat’s brain is estimated to have roughly double that).

Come to think of it, it does make sense to have a brain down there controlling the complexities of digestion, assimilation, elimination.


Similar to our central nervous system, there is also the manufacture, circulation and regulation of many neuro-transmitting hormones in the gut, that were previously thought to be exclusive to the brain.

Serotonin – makes up the majority of this stuff (95%) and is said to be produced in our gut brain. This is the feel good hormone that’s directly responsible for calmness and happiness

Ghrelin – a hormone produced in our stomach and is considered to be the major signaller and controller for hunger and cravings

Dopamine – a signalling molecule for pleasure and reward, the levels of this hormone, half is said to be circulating amongst the gut at any one time.

Interestingly, the gut is also a rich source of benzodiazepines, the family of psychoactive chemicals that includes those popular drugs Valium and Xanax

With over 30 of these neural chemicals circulating through our gut, whether we like it or not, our gut brain plays a major role in human happiness and misery. Only a relative few know this exists.
Stress placed from a repetitive onslaught of bad diet, exposure to pollutants and toxins, even the odd late night alcohol/drug fuelled bender, will influence the way in which these chemicals behave and often trigger things like overeating, mood/behavioural changes and bad decision making. 

Case Study

It’s the morning after a big night and ‘Peter’ has celebrated his birthday in style with plentiful amounts of alcohol and whatever else his inner party animal indulged in. With minimal water before retiring to bed he eventually passes out.

Besides his throbbing headache and dehydration, he wakes up the next day feeling bleary eyed and feeling about as smart as a box of matches. His symptoms include;

  • Insatiable craving for junk foods
  • Lethargic and often irritable mood swings
  • Mild I.B.S also known as a ‘grog bog’
  • Signs of depressive emotional behaviour


Why did Peter suffer such a broad range of unpleasant symptoms?
And are these symptoms believed to have a direct link with inflammation of the gut?

It is shown that the E.N.S (gut brain) takes a particularly hard beating from the effects of drugs and alcohol. Part of this battering involves the disruption of the all important neural hormones of the gut, creating this hormonal imbalance will result in cravings. This has been shown to affect emotions and decision making.

A rapid shift within the gut microbes trigger an inflammatory response from the effects of alcohol sugars and toxicity of drugs. This stress on the gut then create the perfect environment for symptoms of I.B.S and more.

-A study published in ‘The Science Daily’ showed that when mice where put under stress and given access to a range of palatable food, the mice actively sort out fatty foods.

Not that we need to study mice to realise that one, you would have to agree that if a day on the couch with a greasy burger and Netflix is what generally comes after a big night, then this somewhat standard recovery practice for many is in fact evidence of serious neural disruption. A shift to minimise damage from big nights, will undoubtedly lead to better decision making, positivity, moods and eating habits

But really, we all should know this.

The link

The two way link between the gut and brain is undeniable. This pathway is transmitted via the vagus nerve and it is now known that trillions of bacteria down there, can influence and communicate with our brain this way.

‘Did you know your gut actually sends
far more information to your brain than
your brain sends to your gut’

Those butterflies in your stomach when you’re nervous, the upset stomach when you’re angry or stressed even the eating disorders that can come after emotional breakup can all stem from your gut and its communication with the brain. 

Understanding this link is one thing but looking after this whole interconnected bacterial and neural network is a whole other chapter.  

Want to know more?

A cutting edge institute and a major reference point of this article is the The Human Microbiome ProjectIt reports on the mapping of the different types of intestinal bacteria, the relationships they have with each other and what they do for us. Much like how they mapped and discovered out human genes within the body. If you like to read scientific publications with really big words on all things bacterial, this is the site to go to.

Much of the knowledge on the gut brain is still in its infancy and it’s because of ventures like the The Human Microbiome Project that researchers and scientists alike are understanding and connecting the dots more and more.


In the third part of this article we descover things we must try and avoid and measures we must take to ensure adequate gut health.

Click for Part 3



Author: Jake

Bringing you this article, Jake combines his 15 years of expertise in integrated nutrition and fitness to provide his insights on matters of substance.