Dietary fibre is widely found in vegetables, fruits, whole grain cereals and legumes. It mainly consists of indigestible carbohydrates and lignin. It provides physiological and metabolic health benefits in the body. There are two classifications of fibres; soluble (namely viscous) and insoluble fibres which act differently in terms of their physical behaviour in water. Soluble fibre (such as gums, pectins and mucilages) which dissolves in water (hydrophilic), is able to exert prebiotic effects in digestive system. Insoluble fibre (e.g. lignin, cellulose and hemicelluloses) serves as a laxative which can highly contribute to eliminating the fecal matters from the body and hence preventing/reducing constipation.
Epidemiological studies noted that the regular consumption of fibre-rich foods can protect the body against coronary heart disease (CHD) and its major risk factors such as hypertension, obesity, diabetes and dyslipidemia. Soluble fibre is significantly effective in lowering the serum concentration of total and LDL cholesterol as well as regulating the blood sugar swings in the body. The protective effects of soluble fibre on cholesterol catabolism is mainly attributed to its ability of increasing the intestinal viscosity which helps decrease the absorption of bile acids (by binding to bile acids in small intestine and excreting them from the body). Furthermore, the fermentation of soluble fibre in large intestine results in generating short-chain fatty acids and gases which facilitates reducing the production of cholesterol in addition to exhibiting anti-inflammatory activity in the colon.
Whole-grain cereals may be the most protective sources of fibrous diet. Research demonstrated that high levels of the whole-grain intake are correlated with significantly lower incidence of CHD. The significant effects of the ingested oat fibre on reducing the blood pressure have been reviewed by several studies. Other research found the significant effects of fruits and vegetables on attenuating the progression of atherosclerosis. The inverse relation between dietary fibre intake and obesity can be in response to the satiety or incomplete/delayed intestinal absorption.
Frequent intake of dietary fibre is incrementally recommended by dieticians and physicians. The acceptable recommendation of dietary fibre intakes for adults and children (above one year old) are currently 14g of fibre per 1000 kilocalories. The daily recommendation of fibre intakes are 36g for men and 28g for women.