I've had 'IBS' all my life. In reality I think that was a catchall diagnosis for me just drinking too much and eating badly. In the later years I developed IBSc and have been to A&E with it (to no avail, long story).
'IBS' is to me a kind of
'We don't know, so we'll guess it's down to mental health and call it a syndrome' diagnosis.
Mental health does, I believe have an influence on your gut action, as seretonin acts as a form of communication in your gut as well as your head, I believe. I've no doubt there is some connection here with the gut/brain axis.
However, I'd say the connection is nebulous and not understood and it's dismissive to just lump it all in as 'idiopathic' and a 'syndrome.'
A huge amount of things can effect your gut, all the way along it's length. One of the most obvious is the crap carb laden diet we invariably gravitate towards. Many people will be suffering from dysbiosis, whereby their gut biome is destroyed. Antibiotics and medical scans don't help this.
Personally, I'm taking a good quality probiotic and also an inulin supplement as a prebiotic adjunct, as well as eating a good balance of prebiotic vegetables. This hopefully helps in the production of butyric acid which can then provide the colon cell walls with sustenance in an effort to maintain gut health.
Butyric acid is a fatty acid that's created when bacteria in your gut break down dietary fiber. It's also found in lower amounts in some foods. Research suggests it may benefit your digestive health.
www.healthline.com
I think if you take a probiotic then it's also worth ensuring your diet contains enough prebiotic material (a mix of good quality soluble and insoluble fibres) so the little guys have enough to feed on.
I do also take medication, which I alter the dose of myself as required.
Personally I do not believe that exercise has any direct effect on 'IBS' or colon health whatsoever, but ofc it has an indirect effect by promoting general health.
And hydration is necessary with a diet rich in prebiotics too. I struggle with this due to other medical concerns.