Effect of resistant starch on colonic fermentation, bile acid metabolism, and mucosal proliferation

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Abstract
Resistant starch is by definition that part of starch that escapes digestion 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 contents 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 starch. During amylomaize consumption, breath hydrogen excretion rose 85% and fecal short chain fatty acid output increased 35% (PP=0.002). Subsequently, cytotoxicity of the aqueous phase of feces—as measured on a colon cancer cell line—decreased (P=0.007). Colonic mucosal proliferation in rectal biopsies (proliferating cell nuclear antigen immunostaining) decreased from 6.7 to 5.4% (P=0.05). We speculate that resistant starch consumption decreases colonic mucosal proliferation as a result of the decreased formation of cytotoxic secondary bile acids, which is possibly mediated through acidification of the large bowel by production of short-chain fatty acids.