Dietary Fibers and their Role as Functional Food for Human Health: Food Fibers and Human Health

Introduction

Ancient Greek physicians had some knowledge of prevention of constipation by using food items that had bulked excretions (British Nutrition Foundation, 1990). Fibers are the components of plant material that resist the human digestive enzymes. According to the Institute of Medicine which contains the dietary fiber can be defined as the non-digestible carbohydrates and lignin that are intrinsic and intact in plants; whereas the functional fiber consists of isolated, non-digestible carbohydrates that have beneficial physiological effects in humans and total fiber is the sum of both. According to the American Association of Cereal Chemists the dietary fiber is the edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine and as per this association the dietary fiber includes polysaccharides, oligosaccharides, lignin and associated plant substances. Dietary fibers promote beneficial physiological effects including laxation, blood cholesterol attenuation and blood glucose attenuation. The codex committee on nutrition and foods for special dietary uses defines dietary fiber (adopted as Codex definition, July 2009) as carbohydrate polymers with ten or more monomeric units that are not hydrolyzed by the endogenous enzymes in the small intestine of humans. They are classified into the following categories (Daniel, 2006; Lupton, 2010):

• 1.

  Edible carbohydrate polymers naturally occurring in the food.

• 2.

  Carbohydrate polymers which have been obtained from raw food material by physical, enzymatic or chemical means.

• 3.

  Synthetic carbohydrate polymers. The indigestible portion of food derived from plants is termed as dietary fiber (roughage) and it has two main components, soluble fiber and insoluble fiber.

Where patients are on hospital stay, post-operation, bedridden, pain medication control, etc constipation should be watched to prevent unwanted complications such as bowel impaction, vitals instability, hemorrhoids or even death as a result of straining and consequent vagal stimulation. Easy way to prevent those complications is through anticipatory interventions like high fiber diet. Such dietary fiber helps in keeping intestinal and bowel health in good condition. Hence the current chapter deals with major sources of dietary fiber, major health benefits of dietary fiber, recommendations and guidelines for the dietary fiber intake and effects of various food processing operations on the quality of dietary fiber (Daniel, 2006).

Sources Of Dietary Fibers

Eating of significant quantity of dietary fiber will help to keep the good health. Man, women and children will need different amount of fiber in their food. Main sources of fibers are plants and fibers are classified into two types: soluble and insoluble. Both kinds of fibers are important for optimal health (Association of Official Analytical Chemists, 1980; Indian Standard Institution, 1985). Fruits, vegetables and whole grains are rich sources of fiber and can be eaten directly or can be used to make supplements and fiber-rich processed foods. It was observed that fiber content in the meat is negligible compared to the plant sources. The Academy of Nutrition and Dietetics, USA recommends for the consumption of variety of fiber-rich foods. Some of the fibers are listed in the Table 1.