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Food components of different chemical structure which attain the colon without being attacked by digestion and absorption during their transit through the small intestine are defined as dietary fibre. In the colon they serve as energy or nutrient source for the intestinal microflora or are excreted without change. Not only chemical structure is decisive when a food component has to be assigned to either nutrients or dietary fibre: Substances resisting small intestine digestion due to the lack of corresponding catabolizing enzymes in man are supposed to be "obligate" dietary fibre. "Potential" dietary fibre are nutrients which are only partially digested in the small intestine. Lactose--the main carbohydrate of milk--represents a typical potential dietary fibre. The present paper investigates the factors being responsible for both the degree of lactose utilization in the small intestine and its efficiency in the colon.

Carbohydrates are a major component of our food, they are important as body energy stores and they play an important role in cellular structures. In the present paper a classification of food carbohydrates, of dietary fibers and sweeteners is presented and the major physiological effects are discussed. Furthermore, the significance of carbohydrates for the etiology and the treatment of nutrition related diseases which are closely related to the development of arteriosclerosis is outlined. Carbohydrates are beside fat the major determinants of the daily caloric intake. This illustrates their impact on the development of obesity with its predominant role as a risk factor for the development of cardiovascular disease. Furthermore, the role of sugar consumption in the relation to dental caries is stressed. Also the central role of carbohydrate consumption for the treatment of diabetes mellitus is described. Problems of the diabetes diet, the role of the dietary fiber in the treatment of different diseases and the necessity of sweetness in nutrition are discussed in greater detail.