Lack of fiber is the main dietary cause of diverticulitis, so opt for foods rich in fiber: wholemeal bread, cereals, wholemeal pasta and rice, green beans, spinach, sweet potatoes, cabbage, onions or broccoli, legumes such as beans, chickpeas, lentils and peas, nuts, apples, pears, plums, mango, bananas, figs, red fruits or pineapple.