Purpose: The results of previous studies of colorectal neoplasia and fecal composition have been inconsistent, in part because the cases have been symptomatic and the studies small. We sought to test hypotheses relating to fecal bile acids, calcium, and pH in a large sample of asymptomatic subjects who had participated in fecal occult blood screening.
Methods: Fecal samples were obtained from 45 cases of cancer, 129 subjects with adenoma, 167 fecal occult blood-negative controls and 155 fecal occult blood-positive subjects in whom no cancer or adenoma was found. Concentrations of fecal bile acids, steroids, calcium, and pH were assessed blind to case-control status and compared between cases and 1) fecal occult blood-negative controls and 2) fecal occult blood-positive subjects.
Results: No association between colorectal cancer and fecal bile acids or pH was observed. Although there was no overall association between colorectal adenomas and fecal bile acids or pH, villous adenomas were associated with increasing concentrations of major bile acids and decreasing concentration of minor bile acids, and there was a suggestion of an inverse association with an acid pH. High levels of fecal calcium were associated with a reduced risk of both colorectal cancer and adenoma, but this was not statistically significant.
Conclusion: The study does not support an association between colorectal cancer and fecal bile acids or pH. However, there is evidence that increases in major bile acids are associated with villous adenomas.