I didn’t really look at the effects of removing the whole gut, only the microbial populations. However I did do a little research on colitis and the gut microbiome once and people who get partial colonectomies do have less microbial diversity in the gut and experience more metabolic problems as a result of this. They also score lower in cognitive intelligence tests, especially after total removal of the colon. Although it seems that the gut microbiome is intrinsically connected with the brain it’s still not 100% certain what the exact effects of the bacteria are on the brain so it can sometimes be hard to determine cause and effect even in germ free mice studies.

I wrote my dissertation on how the gut microbiome can be involved with neurological disorders such as autism and Parkinson’s. The gut-brain axis is still a system that needs a lot of research but they have found that byproducts produced by gut bacteria can have an influence on the enteric nervous system that is made up of sympathetic and parasympathetic nerves that are connected to the peripheral nerves and therefore the central nervous system including the brain. There are many studies on it, interesting ones are on germ free mice, lab raised mice that aren’t colonised with bacteria at birth and raised in a germ free environment.