This study was performed to examine the effect of dietary polyphenols on fecal secondary bile acids, such as deoxycholic acid and lithocholic acid, the risk factors of colon cancer, in rats fed a high-fat diet. In experiment 1, rats were fed a 30% beef tallow diet containing 0.5% polyphenols for 3 weeks. Dietary curcumin and caffeic acid significantly reduced the fecal concentration of deoxycholic acid. Dietary caffeic acid, catechin, rutin, and ellagic acid significantly reduced fecal lithocholic acid. Fecal hyodeoxycholic acid, a metabolite of lithocholic acid, was markedly lowered by dietary curcumin, caffeic acid, catechin, and rutin. In experiment 2, rats were fed a 30 or 5% beef tallow diet with or without the addition of 0.5% curcumin. In the rats without receiving curcumin, the fecal level of deoxycholic acid was significantly higher in the high-fat diet group than in the low-fat diet group. Fecal deoxycholic acid was significantly reduced by dietary curcumin in the high-fat diets but not in the low-fat diets. The results suggest novel effects of some polyphenols favorable for colon health by reducing secondary bile acids in animals fed a high-fat diet.

Recently, it has often been reported that certain polyphenols are useful for prevention of obesity. However, few investigations have been conducted on the anti-obesity effects of boysenberry polyphenols, including anthocyanins and ellagic acid. Therefore, we examined whether boysenberry juice BJ would prevent obesity in Wistar rats fed normal and high-fat diets containing 5 BJ for 12 weeks. At the end of the feeding period, our data revealed significant decreases in body weight gain, body fat accumulation, and liver lipid levels, especially triglyceride TG and total cholesterol, in the rats fed diets containing 5 BJ BJ group compared with the rats fed diets without BJ control group. Furthermore, we measured the plasma TG levels in rats fed each test diet after a 20-hour fast, and observed notable reductions in the postprandial plasma TG levels in the BJ group compared with the control group after 3 hours. These results suggest that consumption of BJ has potential preventive effects against obesity induced by a high-fat diet and associated metabolic syndrome.