Fiber and Nutritional Health

Populations that consume more dietary fiber have less chronic disease. According to the 2002 Dietary Reference Intakes (DRIs), dietary fiber includes carbohydrates and lignin that are intrinsic and intact in plants that are not digested and absorbed in the small intestine. Functional fiber consists of isolated or purified carbohydrates that are not digested and absorbed in the small intestine that confer beneficial physiologic effects in humans. Total fiber is the sum of dietary fiber and functional fiber. Fibers alter laxation, attenuate the rise in blood glucose, and normalize blood cholesterol. The solubility of fibers was originally thought to determine physiologic properties, with soluble fiber linked to cholesterol-lowering properties and insoluble fiber linked to laxation effects. The DRI Committee recommended that other descriptors for fiber be developed, suggesting viscosity and fermentability. Manufacturers are allowed to list total dietary fiber, soluble fiber, and insoluble fiber on the Nutrition Facts panel. DRIs recommend consumption of 14 g of dietary fiber per 1,000 kcal based on epidemiologic studies showing protection against cardiovascular disease. Usual intake of dietary fiber is only 15 g/day. Even with a fiber-rich diet, a supplement may be needed to bring fiber intakes into the recommended range. Dietary messages to increase consumption of high-fiber foods such as whole grains, pulses, fruits, and vegetables should be broadly supported by the medical profession.   This review contains 3 Tables and 38 references Key words: constipation, diarrhea, dietary fiber, health claims, laxatives, plant foods, stool weight, transit time