It was initially hypothesized that resistant starches, i.e., starch that enters the colon, would have protective effects on chronic colonic diseases, including reduction of colon cancer risk and in the treatment of ulcerative colitis. Recent studies have confirmed the ability of resistant starch to increase fecal bulk, increase the molar ratio of butyrate in relation to other short-chain fatty acids, and dilute fecal bile acids. However the ability of resistant starch to reduce luminal concentrations of compounds that are damaging to the colonic mucosa, including fecal ammonia, phenols, and N-nitroso compounds, still requires clear demonstration. As such, the effectiveness of resistant starch in preventing or treating colonic diseases remains to be assessed. Nevertheless, there is a fraction of what has been termed resistant (RS1) starch, which enters the colon and acts as slowly digested or lente carbohydrate in the small intestine. Foods in this class are low glycemic index and have been shown to reduce the risk of chronic disease. They have been associated with systemic physiological effects such as reduced postprandial insulin levels and higher HDL cholesterol levels. Consumption of low glycemic index foods has been shown to be related to reductions in risk of coronary heart disease and Type 2 diabetes. Type 2 diabetes has in turn been related to a higher risk of colon cancer. If carbohydrates have a protective role in colon cancer prevention this may lie partly in the systemic effects of low glycemic index foods. The colonic advantages of different carbohydrates, varying in their glycemic index and resistant starch content, therefore, remain to be determined. However, as recent positive research findings continue to mount, there is reason for optimism over the possible health advantages of those resistant starches, which are slowly digested in the small intestine.