CARBOHYDRATES - SIGNIFICANCE FOR ENERGY-BALANCE AND GASTROINTESTINAL FUNCTION

The 10th edition of the RDA discusses carbohydrates in the context of dietary fiber and digestible carbohydrates, which provide energy, and recommends that more than half the energy requirement beyond infancy b e provided by carbohydrates and that a desirable intake of fiber be ac hieved by consumption of fruits, vegetables, legumes, and whole-grain cereals. The recommendations on digestible carbohydrates are primarily based on the desirability of limiting the intake of fat. An additiona l consideration is the suggestion that excess calories from carbohydra te vs. fat are metabolized and stored with different efficiencies. The scientific basis for recommending an appropriate intake of dietary fi ber is not clearly evident in the current RDA. The association between a high plant food, and thus fiber intake, and lower incidence of card iovascular disease, colon cancer, and diabetes is of interest but diff icult to use to form the basis of specific recommendations for an appr opriate amount of fiber to include in the diet. The importance of fibe r for normal gastrointestinal function provides the best scientific ba sis for developing recommended intake levels. Dietary fiber, as well a s non-digested starch, are the only known dietary components that incr ease stool weight and are the primary substrates for the microflora in the large intestine. Metabolism of this microflora, including product ion of short chain fatty acids that are used by epithelial cells, appe ars to be important for intestinal health, However, the challenge we s till face is to define the parameters of gastrointestinal function tha t are compatible with health.