The Effect of Dietary Xylitol on the Ability of Rat Caecal Flora to Metabolise Xylitol

Abstract

Summary. The effect of dietary xyiitol on the ability ofthe rat caeca! flora lo metabolise xylitol was investigated. Xylitol metabolism in micro-organisms has generally been assessed in terms ofpH change and acid production wbich are often insensitive in demonstrating low rates ofsubstrate utilisation. Using a rapid and sensitive radioisotopic assay. in which '*COj production from lU-'^Cl xylitol was measured, it was possible to show that the caecal microflora obtained from rats can metabolise xylitol. This activity was increased 10, 15, 30 and 40-fold in the caecal flora taken from rats fed diets containing 2'5. 5. 10 and 20% xylitol, respectively.Using the caecal microflora of normally fed rats, the order of'•'COj production from '*C-iabelled sugars and sugar alcohols was glucose > fructose > xylose > sorbitol ? xylitol. The feeding of glucose and fructose did not alter tbe '^COj producing activities, whereas xylose feeding increased xylose metabolism, sorbitol feeding increased sorbitol and xylitol metabolism, xylitol feeding increased sorbitol, xylose and its own metabolism and arabitol feeding increased xylose and sorbitol metabolism. Marked changes were also observed in the population of the caecal flora of xylitol-fed rats, with increases in the number of gram-positive bacteria, compared to rats on a normal diet. Possible mechanisms for these effects involve mutation, selection of micro-organisms capable of metabolising sugar alcohols, and the induction of enzymes involved in sugar alcohol metabolism. INTRODUCTIONThere now exists considerable scientiftc and commercial pressure to introduce xylitoi into our diets in greater than normal quantities in order to reduce the incidence of dental caries, a major health problem in our society (Scheinin and Makinen, 1975;Makinen, 1978; Counsell, 1978). This is because the total or partial substitution of dietary sucrose by xylito] considerably reduced the incidence of dental caries in volunteers who participated in a two-year trial in Turku, Finland (Scheinin and Makinen, 1975).

Modulating effect of dietary carbohydrate supplementation on Candida albicans colonization and invasion in a neutropenic mouse model

“…The higher cecum percentages observed in the xylitol group indicate the presence of a simpler flora (19,45). A shift to an increased fecal proportion of grampositive versus gram-negative organisms has been described by others for animals receiving xylitol (22,33,35). In fact, we have seen the disappearance of nonlactose fermentors from the stools of mice receiving xylitol in previous experiments (39a).…”

“…In two of these, the mice were allowed free access to drinking water that contained either D-(+)-glucose (Sigma Chemical Co., St. Louis, Mo.) (n = 10) or xylitol (Sigma) (n = 12) each at 5% (wt/vol) concentration from day 16 to day 21 and at 10% thereafter until sacrifice (22,44). The control group (n = 14) received water without carbohydrates.…”

Selection for Streptococcus mutans with an Altered Xylitol Transport Capacity in Chronic Xylitol Consumers

“…The mechanism by which the constitutive fructose-PTS-negative strains arise is not known. A mutation is most unlikely, since it has been shown, in vitro and in vivo, that xylitol and its metabolites are non-mutagenic (Batzinger et al, 1977;Krishnan et al, 1980). Furthermore, it was shown (Gauthier et al, 1984) that the in vitro acquisition of the xylitol resistance phenotype was an adaptive process.…”

Gut Microbiome Toxicity: Connecting the Environment and Gut Microbiome-Associated Diseases

“…For example, cyclamate, which is currently banned in the USA, can be metabolized by gut bacteria into cyclohexylamine, which is carcinogenic [63]. Artificial sweeteners stevioside and xylitol can also be metabolized by the gut bacteria [64,65]. Several studies have demonstrated that some artificial sweeteners and emulsifiers were able to induce gut microbiome toxicity with potential gut microbiota-related health consequences.…”