What does our mental health & our gut have to do with who we are?

I am so astonished about all the findings now-a-days that suggest
that Mental health is so much more connected with our physical
health than we think. On my journey to figuring this out for
myself, I have discovered that seemingly physical symptoms like
unexplained aces or feeling tired have a lot to do with our mental
state and also a direct connection to our gut. Some think that
mental health just affects a few but what if we all have mental
health problems in our lives as well as we have physical health
issues?