In the past, people who made a point of eating a lot of dietary fibre were sometimes the source of ridicule. Once it was shown, however, that eating fibre could prevent or correct certain health problems, it became clear that all of us should increase our fibre intake.
What's the purpose of dietary fibre?
Dietary fibre increases fecal bulk, thus helping the body to eliminate waste. Fibre does this by absorbing several times its weight in water while passing through the small intestine. By the time fibre reaches the large intestine, it is still intact and thus has not been used as nourishment for the body. In the large intestine, fibre is attacked by bacteria, which transform it into substances capable of stimulating the expulsion of stools from the intestine.
Where can you find dietary fibre?
Meat doesn't contain any dietary fibre, only plants do. So people should eat plenty of fruit, vegetables, legumes and whole grains to get the fibre they need. The recommended daily fibre intake is 20 to 30 grams from "natural" products (e.g., unpeeled fruits and vegetables, unrefined foods). These foods contain more fibre than those that have been transformed (e.g., fruit/vegetable juice, products made with white flour). People who are not accustomed to eating large amounts of fibre should increase their intake gradually, to prevent the formation of gas. There are two types of dietary fibre: soluble and insoluble (e.g., seeds, wheat germ). While all fibre is healthy and helps prevent constipation, soluble fibre-fruit, vegetables, barley, rice, rye, etc.-also stops the absorption of certain substances, such as sugar and cholesterol, into the blood.
Psyllium, which is found in several natural laxatives (e.g., MetamucilTM), is also an excellent source of fibre.
What role does fibre play in the prevention or control of certain diseases?
When combined with large fluid intake (1.5-2 litres/day), dietary fibre helps regulate stool frequency by increasing fecal bulk. On the other hand, if liquid intake is too small, fibre can worsen, rather than improve, this problem.
Soluble fibre tends to slow the stomach's movements, thus preventing rapid emptying of its content. At the same time, soluble fibre delays sugar absorption and helps reduce the need for insulin.
Fibre binds to cholesterol, thus stopping its absorption into the blood. The complex remains bound until both are eliminated in the stools.
This disease of the intestine affects around 30 to 40% of adults 50 years and older. It is characterized by the formation of small pouches (diverticula) in the intestine. If stools accumulate in these pouches, the area become inflamed and painful. A high-fibre diet can help avoid this problem.
Not only does insoluble fibre help eliminate carcinogenic substances more quickly, but it also plays a role in the prevention of colon cancer.