Comparative effects of three resistant starch preparations on transit timeand short-chain patty acid production in rats

A high-fiber diet may protect against colon cancer because of the butyrate generated in the colon by bacterial fermentation of nonstarch polysaccharid es. Butryrate can reverse neoplastic changes, at least in vitro, and resist ant starch (RS) represents a source of butyrate in vivo. We examined the ef fects of replacing normal maize starch in the diet of rats with three prepa rations of RS on the amounts of starch, butyrate, and other short-chain fat ty acids in the cecum. We examined the effects on fecal bulking and transit time, which have been suggested to protect against colon cancer. The RS pr eparations that we tested were potato starch, high-amylose maize starch, an d an alpha-amylase-treated high-amylose maize starch. All had major effects on fecal weight and on the weight of the cecum but only slightly shortened transit times. All increased the amount of starch reaching the cecum and i ncreased short-chain fatty acid production in the cecum; potato starch had the greatest effect and high-amylose maize starch the least. Potato starch, unlike high-amylose maize starch, enhanced the proportion of butyrate. Thu s there were marked differences among sources of RS, even though these were all classified as RS2. The significance for colon cancer is discussed.