Digestion, absorption, fermentation, and metabolism of functional sugar substitutes and their available energy
Many kinds of oligosaccharides and sugar alcohols have been newly developed as bulking sugar substitutes that have beneficial health effects. A sugar substitute that is not digested and absorbed in the small intestine reaches the large intestine, where it is completely fermented by intestinal bacteria and produces short-chain fatty acids, which are converted to energy. The available energy of a nondigestible sugar substitute, which is completely fermented by intestinal microbes, is estimated as approximately 2 kcal/g. On the other hand, a sufficiently high ingestion of nondigestible sugar substitutes regularly causes overt diarrhea in human and animals. However, the diarrhea disappears within a few days because intestinal microbes, which readily utilize these saccharides, increase during ingestion. The maximum permissible dose, by which transitory diarrhea is not caused by the ingestion of nondigestible sugar substitutes, is estimated as approximately 0.3 g per kg body weight in single ingestion for Japanese adults. The value is varied by some factors, such as separate ingestion, repeat ingestion, test substance, and body condition, etc.