Gastrointestinal Disturbances Associated with the Consumption of Sugar Alcohols with Special Consideration of Xylitol: Scientific Review and Instructions for Dentists and Other Health-Care Professionals

Abstract

Sugar alcohols (polyols) are used in food manufacturing and in medical tests and examinations. d-Glucitol (sorbitol) and d-mannitol were previously the most common alditols used for these purposes. After the 1960s, xylitol became a common ingredient in noncariogenic confectioneries, oral hygiene products, and diabetic food. Erythritol, a polyol of the tetritol type, can be regarded as the sweetener of the "next generation." The disaccharide polyols maltitol, lactitol, and isomalt have also been used in food manufacturing and in medical tests. Consumption of pentitol- and hexitol-type polyols and disaccharide polyols may cause gastrointestinal disturbances at least in unaccustomed subjects. The occurrence of disturbances depends on consumer properties and on the molecular size and configuration of the polyol molecule. Adaptation may take place as a result of enzyme induction in the intestinal flora. Some of the literature on xylitol has been difficult to access by health-care professionals and will be reviewed here. Research and clinical field experience have found no pathology in polyol-associated osmotic diarrhea-the intestinal mucosa having normal basic structure, except in extreme instances. Xylitol is better tolerated than hexitols or the disaccharide polyols. Erythritol, owing to its smaller molecular weight and configuration that differ from other alditols, normally avoids the gastrointestinal reactions encountered with other polyols. This review will also touch upon the FODMAPs diet concept.

Figure 1

Relationship between the metabolism of xylitol and glycolysis in humans. The scheme describes the metabolism of dietary xylitol in broad outline only. The body receives energy from glycolysis (the thick horizontal arrow). The first intermediate of glycolysis is glucose 6-phosphate which forms an important link between glycolysis and another metabolic pathway, called the pentose phosphate shunt, or pentose phosphate cycle (curved arrow). The thinner black arrow represents the glucuronate-xylulose cycle of Touster. The differences in the thickness of the arrows reflect the relative portion of these three pathways in the overall metabolism. Although the significance of the Touster cycle is minor from the energetic point of view, it is nevertheless absolutely necessary for body functions. Pyruvic acid which may be regarded as the end product of glycolysis can be further metabolized in two ways: reduction to lactic acid under conditions of limited oxygen supply, or becoming a part of coenzyme A when the oxygen supply is sufficient. The scheme shows how xylitol can contribute to the overall energy metabolism of the body. The original scheme of Bässler [67] was modified and completed by the present author.

Figure 2

Gradual lessening of osmotic diarrhea and flatulence in human subjects who consumed on the average 67 g of xylitol daily for two years. The results are here shown for the first 140-day period. The ordinate gives the number of subjects complaining even about slight diarrhea or increased defecation frequency on each test day. The initial peaks of consumption were found to result from the interest of the subjects to get acquainted with the new dietary regimen. Modified from [4].