Fecal ammonia in patients with adenomatous polyps and cancer of the colon.

The correlation between high intakes of protein and high incidence of human colonic cancer is unexplained. Appreciable amounts of ammonia are generated in the large bowel through bacterial degradation of proteins and peptides, and experimental studies indicate that ammonia may select for neoplastic growth. Fecal concentrations of ammonia did not differ among 17 patients with former colonic adenomas [40.6 +/- 4.5 (SE) mM], 17 patients with former colonic cancer (51.4 +/- 3.9 mM), and 16 healthy controls (46.4 +/- 6.1 mM). By use of an in vitro fecal incubation system, possible alterations in bacterial fermentation and formation of ammonia were investigated. Fecal suspensions were incubated for 6 and 24 hours with and without addition of fermentable substrates (ispaghula husk, wheat bran, albumin, and glucose; 10 mg/ml). The in vitro production of ammonia in unsupplemented fecal homogenates from both groups of patients was comparable with the production found in homogenates from healthy controls, and the response to fermentable substrates was similar in all three groups. Addition of albumin caused a marked increase in the production of ammonia, and addition of glucose increased bacterial assimilation of ammonia considerably. These well-known characteristics of bacterial metabolism of ammonia apparently did not differ between healthy individuals and patients investigated more than three months after colonoscopic polypectomy or colonic cancer resection.