What is dietary fiber?

Dietary fiber is an umbrella term for a heterogeneous mixture of plant food components that indigestible in the small intestine. Dietary fiber includes plant cell wall substances (cellulose, hernicellulos, pectin, and lignin) as well as intracellular polysaccharides such as gums and mucilages resistant to digestion by the alimentary enzymes of humans.

Dietary fiber is available in the human diet through a wide variety of food sources such as both raw and processed cereals, vegetables, legumes and fruits.

Fiber offers a variety of health benefits and is essential in reducing the risk of chronic diseases such as diabetes, obesity, cardiovascular disease and diverculitis.

The best accepted beneficial effect of dietary fiber is relief of constipation. Wheat bran, in particularly has been shown to be helpful in maintaining regularity. Some types of fiber including pectin, gaur gum, and the fibers found in oat products psyllium and legumes - reduce blood cholesterol levels to a small but measurable extent.

According to the Institute of Medicine (IOM), adequate intake (AI) of total fiber should be 14kg/1000 kcal.
What is dietary fiber?