Importance of Dietary Fiber

Fibre forms the skeletal system of plants. Without it no plant or tree would be able to stand upright. Dietary fibre, the roughage of yesteryears, consists of those parts of the plant foods that cannot be digested by enzymes or other digestive secretions in the ailmentary canal.

Dietary fibre plays an important role in the maintenance of health and prevention of diseases. There is sufficient evidence to suggest that an artificial depletion of fibre as in case of refined cereals and sugar has over the last 100 years contributed to several degenerative diseases. Recent studies in this area indicate that sufficient intake of fibre-rich diet may help prevent obesity, colon cancer, heart disease, gallstones, irritable bowel syndrome, diverticulosis and diabetic conditions.

Studies have also established that dietary fibre is a collection of elements with a variety of functions rather than a single substance with single function as was assumed earlier. This new insight into the true nature of fibre has given the lie to old beliefs that bran is synonymous with fibre, that all fibre is fibrous or stringy and that all fibre tastes the same.

Physiological effects

Fibre in the diet promotes more frequent bowel movements and softer stools having increased weight. The softness of stools is largely due to the presence of emulsified gas which is produced by the bacterial action on the fibre. A high fibre intake results in greater efficiency in the peristaltic movement of the colon. This helps in relieving the constipation which is the main cause of several acute and chronic diseases.

Recent studies suggest that increasing the dietary fibre intake may be beneficial for patients with irritated bowel syndrome who have diarrhea and rapid colonic transit, as well as to those who have constipation and slow transit. The high fibre diet, like bran, thus regulates the condition inside the colon so as to avoid both extremes - constipation and diarrhea.

Investigations have shown that several potential carcinogens are produced in the faeces. Their production is related to the acidity of the gut content. The greater the acidity in the bowel content, the less is the production of these carcinogens. The breaking down of the fibre by bacteria renders the faeces more acidic. This reduces the amount of possible carcinogenic substances. Fibre also reduces the possibility of formation of harmful toxins in the large intestine by reducing the intestinal transit time of the food contents.

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 0.5-1.5, 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, hermicellulose 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 time, iron and vitamins and containing a considerable amount of protein.

Dr.Dennis P. Burkitt, a noted British physician remarks, " Grain roughages, such as rich bran and wheat bran, are an essential part of a healthy diet, and a preventive against diseases like piles, constipation, bowel cancer, varicose veins and even coronary thrombosis. " Dr. Burkitt worked for many years in Africa and found after a series of observations that rural Africans who eat bulk of fibrous foods rarely suffer from any of these diseases.

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.