Check for Celiac disease. It can cause all of these problems - well, the diverticulosis would be from constipation, which Celiac can cause. Get the blood tests for Celiac. If that's the cause, going on a gluten-free diet will make the patient feel much better on all counts.
As the conditions you mentioned are different diseases, no one medication would help.
I would encourage the patient to follow the directions given by the health professional he/she has the most confidence in. I would avoid medication advice dispensed on the internet.