Re: Sweetening Kefir w/Xylitol

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3876090/

Xylitol Affects the Intestinal Microbiota and Metabolism of Daidzein in Adult Male Mice

XD = Xylitol Diet
CD = Daidzein-containing control diet

It has been shown that xylitol feeding caused a clear shift in rodent fecal microbial populations from Gram-negative to Gram-positive bacteria [21]. In human volunteers a similar shift was observed even after a single 30-g oral dose of xylitol [21].

It has been confirmed that human intestinal microbiota predominantly consists of members of approximately 10 phylogenetic bacterial groups and that these bacterial groups can be distinguished by the T-RFLP system developed by Nagashima et al. [37,38]. We used this Nagashima method [37,38] although it cannot completely distinguish between Gram-negative and Gram-positive bacteria. However, in our results, the occupation ratios of Bifidobacterium tended to increase in the XD group. Bifidobacterium belongs to Gram-positive bacteria.

The occupation ratios of Prevotella tended to increase in the XD group. There are few reports with respect to the effects of dietary xylitol on Prevotella. We cannot explain this phenomenon

Some diets affect the composition of intestinal microbiota [39]. It has been reported that diet affects the microbiota in terms of both structure and gene expression [40]. Switching from a low-fat, plant polysaccharide-rich diet to a high-fat, high-sugar “Western” diet shifted the population of the microbiota within a single day, changed the representation of metabolic pathways in the microbiome, and altered microbiome gene expression [40]. It has been reported that dietary fat significantly affects intestinal microbiota [40,41]. In our result, the XD diet significantly affected the fecal lipid contents. Differences in lipid concentrations of the gut also might affect the composition and/or metabolic activities of intestinal microbiota.

A limitation of our study was that we could not identify what kind of intestinal bacteria were stimulated by the supplementation of dietary xylitol in vitro. Further studies are needed to clarify these effects.

4. Conclusions
In conclusion, plasma total cholesterol concentrations were significantly lower in the XD group than in the CD group. Urinary amounts of equol were significantly higher in the XD group than in the CD group. The fecal lipid contents (% dry weight) were significantly greater in the XD group than in the CD group. The cecal microbiota differed between the two dietary groups. The occupation ratios of Bacteroides (OTUs 469, 853) were significantly greater in the CD than in the XD group (p < 0.05). This study suggests that xylitol has the potential to affect the metabolism of daidzein by altering the metabolic activity of the intestinal microbiota and/or gut environment. Given that equol affects bone health, dietary xylitol plus isoflavonoids may exert a favorable effect on bone health.
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