Dietary fibre is made up of the constituents of plants which are resistant to digestion by the human gastrointestinal tract. Fibre increases the bulk of the faeces, it speeds the transit of bowel contents and is said to protect the body from the effects of cancer producing substances contained in some foods. A diet high in fibre protects against cancer of the large bowel, diverticular disease, chronic constipation and associated haemorrhoids, appendicitis and the irritable bowel syndrome. In diabetes it has become apparent that blood sugar levels are more easily controlled by the use of dietary fibre. Fibre in the diet is said to lower the levels of cholesterol thus protecting against coronary artery disease.
Oatmeal bran restricts the absorption of cholesterol - a convenient form is oatmeal porridge.
Apparently wheat bran does not but it can replace some of the fat in the diet and have a beneficial effect indirectly. Fruit and vegetables all play their part in protecting the heart. A mixed diet including fruits, vegetables, whole grain bread and cereal might be preferable to unprocessed bran which is said to interfere with the absorption of calcium, zinc and iron. Some people find unprocessed bran unpalatable. Abdominal discomfort may be increased by excessive production of intestinal gas which produces abdominal swelling and flatulence.