Effect of dried plums on colon cancer risk factors in rats

Dried plums (that is, prunes) are a fruit that show promise as a food to lower colon cancer risk, based on their high content of dietary fiber and polyphenolics. In this study, we have examined the effect of diets containing dried plums on the number of colonic precancerous lesions (aberrant crypts, ACs), fecal bile acid concentration, and cecal bacterial enzyme activities related to colon cancer risk. Rats were fed one of four diets: a basal diet (a modified AIN-93G diet), a low-concentration dried plum diet (LCDP, 4.75% dried plum powder), a high-concentration dried plum diet (HCDP, 9.5% dried plum powder), or a diet matched to the carbohydrate content of the HCDP diet (CH-M) for 10 days. All animals were then administered azoxymethane (15 mg/kg, s.c., given two times, 1 wk apart) and fed their respective diets for 9 additional weeks. The number of AC foci (ACF), large ACF (>3 AC/ACF), or ACF multiplicity (AC/ACF) did not differ among the four groups. When compared with the basal diet, rats fed the LCDP diet had significantly lower concentrations of total fecal bile acids, deoxycholic acid, and hyodeoxycholic acid. Rats fed the HCDP diet had significantly lower fecal concentrations of lithocholic acid and hyodeoxycholic acid. The LCDP and HCDP diets significantly decreased the cecal activity of 7alpha-dehydroxylase, and the LCDP also had lower beta-glucuronidase activity. The LCDP, HCDP, and CH-M groups had significantly greater cecal nitroreductase activities than the basal group. There was a significant correlation between 7alpha-dehydroxylase activity and fecal lithocholic acid concentration. Compared with the basal diet, both the LCDP and HCDP diets greatly increased cecal supernatant oxygen radical absorbance capacity (ORAC). These results suggest that, although dried plums did not reduce ACF number, they favorably altered other colon cancer risk factors.