How much Metamucil to prevent diverticulitis?

If you eat. Adequate fiber in your diet, ie fruits vegetables salads, whole grains, don't waste your money on metamucil or other fiber substitutes and don't forget to drink 80-100 oz of caffeine free/alcohol free fluid daily. Fluid is necessary for fiber to work properly. Even so this will not prevent 100% of the cases of diverticulitis but it will reduces your chances.
3 doses a day. Though i think that a high fiber diet &/or metamucil prevents diverticulitis, it is not conclusively proven. Diverticulitis is a peridiverticular infection while diverticulosis is the condition of having diverticulae. 3 doses of metamucil a day will prevent the formation of diverticulae.