Talked to my wife about this thread. She says she makes sure she ingests at least 20 servings of fibre a day. She is a retired dietician so she knows what she is talking about.
She makes sure that I have at least 12 servings of fibre a day.
An apple a day is great(2x the fibre of a banana). Nuts, beans, peas, bran, oatmeal, fruits, veggies etc etc.
Important as well is getting some exercise as it increases your metabolism. Who knows how much cancer is prevented by eating more fibre(colon cancer, pancreatic cancer etc).
Being aware of what you are eating and how much can make a big difference. Read food labels as well.