fecal levels of shortchain fatty acids and bile acids as determinants of colonic mucosal cell proliferation in humans we studied the correlation between fecal levels of shortchain fatty acids scfa bile acids ba and colonic mucosal proliferation in humans on a free diet subjects n 43 27 men and 16 women 61 7 and 59 6 se yr old respectively were outpatients who previously underwent resection of at least two sporadic colon polyps mucosal proliferation was determined by 3hthymidine incorporation in vitro in three colorectal biopsies obtained without cathartics and was expressed as labeling index li ba were analyzed in feces by mass spectrometry and scfa by gas chromatography we found that increasing levels of ba in feces did not correlate with higher li on the contrary higher levels of scfa were significantly associated with lower li in the colonic mucosa p for trend 002 in conclusion in humans on a free diet intestinal proliferation seems to be regulated by the levels of scfa in feces and not by ba because a lower intestinal proliferation is associated with a decreased colon cancer risk treatments or diets that increase colonic levels of scfa might be beneficial for colonic mucosa