Dietary fibre increases the bacteria in the large intestines, which require nitrogen for their growth. This in turn reduces the chances of cancerous changes in cells by reducing the amount of ammonia in the large bowel. Fibre reduces the absorption of cholesterol in the diet. It also slows down the rate of absorption of sugars from the food in the digestive system. Certain types of fibre increase the viscosity of the food content. This increased viscosity indirectly reduces the need for insulin secreted by the pancreas. Thus a fibre-rich diet can help in diabetes mollitus.
Sources of fibre:
The most significant food sources of fibre are unprocessed wheat bran, whole cereals such as wheat, rice, barley, rye, millets, legumes such as potato, carrots, beet, turnip and sweet potato, fruits like mango and guava and leafy vegetables such as cabbage, lettuce and celery. The percentage of fibre content per 100 gms. of some foods are: bran 10.5-13.5, whole grain cereals 1.0-2.0, nuts 2.0-5.0, legumes 1.5-1.7, vegetables 0.5-.5, fresh fruits 0.5-1.5 and dried fruits 1.0-3.0. The foods, which are completely devoid of fibre, are meat, fish, eggs, milk, cheese, fats and sugars.
Bran, the outer coverings of grains, is one of the richest sources of dietary fibre. And it contains several types of fibre including cellulose, hemicellulose and pectin. Wheat and corn bran are highly beneficial in relieving constipation. Experiments show that oat bran can reduce cholesterol levels substantially-Corn bran is considered more versatile. It relieves constipation and also lowers LDL cholesterol, which is one of the more harmful kinds. Besides being rich in fibre, bran has a real food value being rich in lime, iron and vitamins and containing a considerable amount of protein.
Legumes have high fibre content. Much of this fibre is water-soluble, which makes legumes likely agents for lowering cholesterol. Soyabeans, besides this, can also help control glucose levels.
The types of fibre contained in vegetables and fruits contribute greatly towards good health. The vegetables with the biggest fibre ratings include sweet corn, carrots, potatoes, parsnips and peas. And among the high ranking fruits are
raspberries, pears, strawberries and guavas.
Types of fibres
There are six classes of fibre. They are cellulose, hemicellouse, pectin, gums, mucilages and legnin. They differ in physical properties and chemical interactions in the gut, though all except legnin are polysaceharides. The facts known so far about these forms of fibre as a result of various studies are discussed below.
Cellulose: It is the most prevalent fibre. It is fibrous and softens the stool. It abounds in fruits, vegetables, bran, whole-meal bread and beans. It is also present in nuts and seeds. It increases the bulk of intestinal waste and eases it quickly through the colon. Investigations indicate that these actions may dilute and flush cancer-causing toxins out of the intestinal tract. They also suggest that cellulose may help level out glucose in the blood and curb weight gain.
Hemicellulose: It is usually present wherever cellulose is and shares some of its traits. Like cellulose, it helps relieve constipation, waters down carcinogens in the bowel and aids in weight reduction. Both cellulose and hemiceltulose undergo some bacterial breakdown in the large intestine and this produces gas.
Pectin: This form of fibre is highly beneficial in reducing serum cholesterol levels. It, however, does not have influence on the stool and does nothing to prevent constipation. Researches are being conducted to ascertain if pectin can help eliminate bile acids through the intestinal tract thereby preventing gallstones and colon cancer. It is found in apples, grapes, berries, citrus fruits, guava, raw papaya and bran.
Gums and Mucilages: They are the sticky fibres found in dried beans, oat bran and oatmeal. Investigations have shown that they are useful in the dietary control of diabetes and cholesterol.
Legnin: The main function of legnin is to escort bile acid and cholesterol out of the intestines. There is some evidence that it may prevent the formation of gallstones. It is contained in cereals, bran, whole meal flour, raspberries, strawberries, cabbage, spinach, parsley and tomatoes.
The best way to increase fibre content in the diet is to increase the consumption of wholemeal bread, brown rice, peas, beans, lentils, root vegetables and sugar-containing fruits, such as dates, apples, pears and bananas. The intake of sugar, refined cereals, meat, eggs and dairy products should be reduced. Candies, pastries, cakes which are rich in both sugar and fat, should be taken sparingly. White processed bread should be completely eliminated from the diet.