Effects of resistant potato starch on cholesterol and bile acid metabolism in the rat

This study examines the effects of two types of resistant starch (RS), raw starch from uncooked potatoes and retrograded starch in the form of cooked and cooled potatoes, on cholesterol and bile acid metabolism in rats. Groups of 8 male Wistar rats were fed a semipurified diet containing 15% cellulose, freeze-dried raw potatoes, or freeze-dried cooked potatoes for four weeks. Serum cholesterol, liver cholesterol, and fecal steroid excretion were determined. Serum cholesterol was significantly higher and liver cholesterol was significantly lower in response to the cooked potato diet compared to the cellulose or raw potato diet. Total steroid excretion was significantly higher in rats fed the cooked potato diet (26.31 mg/d) compared to those fed the cellulose or raw potato diet (14.27 mg/d and 16.81 mg/d, respectively) Daily total bile acid excretion was significantly different among the three groups, with highest excretion seen in rats fed cooked potatoes. High daily excretion of lithocholic acid and hyodeoxycholic acid was observed in rats fed cooked potatoes. These results suggest that changes in the cecal microflora and in the production, pool size, and excretion of chenodeoxycholic acid and its derivatives may be responsible for alterations in cholesterol and bile acid metabolism observed with resistant starch feeding. (C) 1997 Elsevier Science Inc.