The Enteric Nervous System, which connects the gut's neurons to the brain neurons, may
subconsciously influence how we perceive the world. It could influence
our levels of anxiety and depression, for example. One hypothesis
suggests even neurological diseases, such as Parkinson's, are believed
to exist first in the neurons of the digestive tract.
A major area of study in the gut is about the bacteria used in digestion. They are just part of the mystery of how our stomach and digestion may have a huge impact on our quality of life. We are
ecosystems... We are more bacteria than we are human. We have more bacteria DNA than human DNA. Bacteria digest 30% of our food into energy.
The bacteria may influence our propencity towards diseases! Three enterotypes (classifications of living organisms) dictate how we convert our food into vitamins. That's why some people have a greater or less disposition for liver disease, diabetes and cardiovascular disease. These enterotypes can be discerned just by examining stool of individuals. Even obesity has been introduced into mice... when other controlling factors have been equalized... by changing the makeup of their gut flora. Other mice have been made more (or less) aggressive by trading gut flora from a mouse at the other end of the aggressive spectrum.
When it comes to willpower, when they removed the bacteria from mice, their behaviour became odd. They take lots of risks. When they add bacteria,
the mice behave better. There is very strong evidence that the microbiota influences the brain. We're being
influenced by the bacteria that has been on earth for millennia. We've
known that parasites have had an influence on the behaviour of
organisms... but now we see there may be many factors... and organisms... at play!
In humans, probiotics are
being examined for their effect on anxiety. There have been tests
showing that changing the intestinal flora changes the subject's
reaction to stress.
https://www.gaia.com/video/gut-our-second-brain?fullplayer=preview
https://www.gaia.com/video/gut-our-second-brain?fullplayer=preview