Health: The Second Brain - Part I

Our Need For Food:

It has been long understood that we can have a strong emotional or psychological need for food as well as the requirement that exists based purely on food's nutritional requirements.  Chemicals produced by the body such as serotonin and dopamine are potential drivers behind this.  

Serotonin is known as the happy hormone, its level affects our mood, appetite and sense of well-being.  Dopamine is known as the pleasure hormone it affects our expectations and has been shown in studies to affect the decision making process.

The Nervous System:

Before I go into more detail let's briefly discuss the nervous system.  In simple terms it is broken down into two areas based on its location within the body.  These are the central nervous system (CNS) and the peripheral nervous system (PNS).  The CNS consists of the nerves within the brain and spinal cord, the PNS consists of the nerves outside the brain and the spinal cord.

There is another part of our nervous system often overlooked until recently that is so complex and intricate; it is not just seen as a subset of the PNS.  It controls the gastrointestinal (GI) tract and is technically known as the enteric nervous system.  It is also termed "the second brain" because of the number of neurons (nerve cells) embedded in the walls of the alimentary canal or gut.  The gut contains 100 million neurons, approximately the same number found in the brain.  

I Can Feel It In The Gut:

Neurons transmit information by the use of electrical and chemical signals.   We often associate chemicals such as serotonin with the brain, but interestingly over 95% of serotonin resides in the gut. In fact nearly every substance that helps run and control the brain also reside in the gut.  Over 30 neurotransmitters (chemicals that send signals to cells) associated with the brain - including dopamine and adrenalin (epinephrine) are found in copious amounts in the gut too.

We are often advised to "follow our gut instinct", experience "butterflies in the stomach" or respond to our "gut feelings" there is more truth to this than just a bunch of often used expressions.  The gut is more than just a digestive system.  It has a vital link to the brain via the vagus nerve.  90% of its information goes from gut to the brain, with only 10% of information being sent from the brain back to the gut.  This reflects the fact that the 'feelings' of the gut can have significant influence over the brain.  The analytical process of decision making can be overridden by the emotional decision making process.

The enteric nervous system can also operate independently from the CNS.  Studies demonstrate even when the primary neural link (the vagus nerve) is severed; the enteric nervous system still continues to function.

Feel Good Factor:

Back to the happy hormone serotonin - it makes you feel good.  It supports emotional health and it directly affects the well-being of your gastrointestinal (GI) tract, other feel good chemicals such as enkephalins and benzodiazepines are also abundant in the gut - these are a form of natural opiates and mood-controllers in the body.  A lack of these hormones may lead to depression and feeling down.  But can also lead to more serious issues.  For example, a lack of dopamine long term can lead to chronic conditions such as Parkinson's disease, where dopamine based neurons levels are almost zero.

As well as not having enough serotonin or dopamine, we can also have too much of a good thing.  Current research in the burgeoning field of neurogastroenterology examines the link between the brain and the gut, the influence on our mental state and the key roles in certain diseases throughout the body.  For example studies show sufferers of irritable bowel syndrome (IBS), autism and osteoporosis have elevated levels of serotonin in the gut.

The gut also has a very important role in terms of mediating the body's immune response.  70% of our immune system is in the gut to kill and repel invaders.  An over-active or under-active immune system can of course have a devastating impact in the vast array of auto-immunity related diseases and a key starting point for promoting chronic systemic inflammation.

Nutrition:

Poor nutrition will affect the sensitivity and function of neurotransmitter receptors, particularly for dopamine and serotonin.  Insufficient tryptophan (due to a lack of protein in the diet), excessive carbohydrate consumption and lack of nutrient absorption can contribute to this lack of function.  

Food will affect not only how you look and perform, but most significantly how you feel.  Making healthy food choices, avoiding processed foods and those foods known to cause inflammation will optimise the health of the gut and lead to a healthy mind and outlook.

I will discuss the nutritional aspect of this in more detail in part two of this article in the near future.

Comments

[Zach Raybould]

Really interesting read and explains a lot of stuff regarding depression and mental health. Please write Part II :)