EFFECT OF RESISTANT STARCH ON COLONIC FERMENTATION, BILE-ACID METABOLISM, AND MUCOSAL PROLIFERATION

Resistant starch is by definition that part of starch that escapes dig estion in the small bowel. Cecal fermentation of resistant starch into short-chain fatty acids will result subsequently in a decrease in pH. Thus, resistant starch may have the same effect on colonic luminal co ntents and mucosa as some fiber components. We studied the effects of adding 45 g native amylomaize (Hylon-VII) to a standardized diet in 14 healthy volunteers on fermentation and colonic mucosal proliferation. Hylon-VII is a high amylose maize starch, containing 62% resistant st arch. During amylomaize consumption, breath hydrogen excretion rose 85 % and fecal short chain fatty acid output increased 35% (P < 0.01). Ex cretion of primaly bile acids increased and the soluble deoxycholic ac id concentration decreased by 50% (P = 0.002). Subsequently, cytotoxic ity of the aqueous phase of feces-as measured on a colon cancer cell l ine-decreased (P = 0.007). Colonic mucosal proliferation in rectal bio psies (proliferating cell nuclear antigen immunostaining) decreased fr om 6.7 to 5.4% (P = 0.05). We speculate that resistant starch consumpt ion decreases colonic mucosal proliferation as a result of the decreas ed formation of cytotoxic secondary bile acids, which is possibly medi ated through acidification of the large bowel by production of short-c hain fatty acids.