Dietary fibers find an important role in the normal functioning of the gut, as well as in maintaining the cholesterol levels in humans. In the last two decades dietary fibers have attracted the attention of researchers and is proving a promising additive in foods as well as in nutraceuticals, but still many aspects of the dietary fibers are yet to be explored and studied. Fibers have recently been classified by the Dietary Reference Intake Committee of the Food and Nutrition Board of the Institute of Medicine of the National Academy of Sciences, Canada as total fiber, which is made up of dietary fiber and functional fiber. The importance of dietary fibers have not been realized by the authorities and so has not been separately classified so far, but has constantly been associated in short term and acute studies with serum cholesterol reduction and reduced postprandial glucose and insulin responses. Ironically, it is the insoluble cereal fiber, which is associated with protection from Coronary heart disease (CHD) and diabetes in cohort studies despite a relative absence of demonstrated metabolic effects. Soluble fibers appear to have their effect by reducing the rate of absorption from the small intestine. Similar metabolic effects have been seen with slowing the rate of absorption by other means such as sipping versus bolus ingestion of glucose, increasing meal frequency, or reducing the rate of glucose absorption by the use of low glycemic index foods. However, in this last case, benefits have also been noted in cohort studies in terms of diabetes and CHD risk reduction. Furthermore benefits also appear in relation to the incidence of certain cancers. Soluble fibers therefore have good reasons to have a range of metabolic health benefits. Their potential uses, mechanisms of action and means of incorporation into diets require further exploration. The intent of this review is to summarize the physiological significance of dietary soluble fiber.
