I believe strongly in the brain-gut connection. Serotonin is made in the gut, for one thing. If there are problems with brain chemicals, neurotransmitters, or electrical signals that affect how the brain functions, it’s likely the gut will be impacted, and vice versa. That said, I’ve had gut issues since early adulthood, and quasi-MAV symptoms for decades, until an acute vertigo/nystagmus incident ran me over two years ago.
Calm IBS? I have IBS-D or BAD (not sure). I’m taking Welchol, bile sequestrant, as it’s believed my issues stem from bile malabsorption. (Even before removal of gallbladder.) I also use Immodium, and even Pepto at times. You can do only so much in modifying diet, exercise, relaxation, counseling, psychotropic drugs, etc. My guts are loud and proud! But I have a chronic history.
A naturopath advised that psyllium powder is our best friend: helps move things along when there isn’t enough moisture, and absorbs moisture when there’s too much. (constipation vs. diarrhea)
Certain forms of magnesium can produce symptoms similar to IBS. When I was super low carb, I took magnesium citrate in tablet form to prevent constipation. I’ve heard many people with bowel issues say they can’t tolerate magnesium supplements. Some, even without bowel issues, are more sensitive to magnesium. I get magnesium in a daily multiple vitamin and in my calcium supplement, so I have to watch it.