We describe our recent studies evaluating the prebiotic effects of indigestible sugar separated from traditionally cultivated beans and potatoes, as well as newly developed chicory harvested in the Tokachi area, Hokkaido, Japan. Our results indicated that the structure of starches in beans can be categorized as resistant starch type 2 (RS2). Rats were found to have reduced digestibility of beans, probably due to the conversion of RS2 to resistant starch type 3 (RS3, retrograded starch) as well as interaction with denatured protein formed during the heating process. We also found that intake of beans facilitated cecal acid-fermentation in rats, increased short-chain fatty acid levels, and lowered pH. Consequently, intake of beans was found to be effective in improving the balance of intestinal flora. Potatoes contain starch composed of esterified phosphorus and RS2, which is most likely converted to RS3 during the heating process. Administration of potato starch also increased cecal short-chain fatty acid levels, particularly butyric acid. The increased production of butyric acid was found to facilitate digestion, resulting in increased amounts of fecal matter. Inulin, derived from chicory harvested in the Tokachi area, was also found to be effective in improving fecal fermentation, probably by increasing Lactobacillus and Bifidobacterium levels, along with increasing total short-chain fatty acid concentrations. These results are in agreement with previous findings. Overall, it was found that beans and potatoes contain resistant starch with distinct properties, and these foods, along with chicory-derived inulin, demonstrated a health-promoting prebiotic effect through improvement of intestinal flora.
Key words : Resistant starch, Prebiotic function, Intestinal flora, Lipid metabolism. |
